Volume 50,Issue 5,2021 Table of Contents
2021, 50(5):1505-1512.
DOI: 10.12442/j.issn.1002-185X.20191103
Abstract:
To investigate the effect of molybdenum (Mo) addition on microstructure and oxidation resistance of CrN coating, Cr-Mo-N coatings with different Mo contents were fabricated on silicon wafers and high speed steel by reactive magnetron sputtering and annealed at elevated temperatures from 500 °C to 800 °C in air for 1 h. The coatings before and after annealing were characterized by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscope (SEM). The results show that the as-deposited CrN and Cr-Mo-N coatings all exhibit B1 face-centered cubic (fcc) phase based on the CrN lattice. Mo ions substitute for Cr ions in Cr-N lattice, forming the solid solution Cr-Mo-N coatings. At 600 °C, XRD and Raman spectra show that the MoO3 phase forms in Cr-Mo-N coatings with higher Mo contents, indicating a coarser surface with higher oxygen content. At 700 °C, the cross sectional morphology of the CrN coating exhibits loose columnar grains with some porous regions due to the internal stress while the Cr-Mo-N coating shows the dense columnar structure. This study reveals that the Cr-Mo-N coatings with lower Mo contents (<17at%) have better oxidation resistance than the CrN coating does.
To investigate the effect of molybdenum (Mo) addition on microstructure and oxidation resistance of CrN coating, Cr-Mo-N coatings with different Mo contents were fabricated on silicon wafers and high speed steel by reactive magnetron sputtering and annealed at elevated temperatures from 500 °C to 800 °C in air for 1 h. The coatings before and after annealing were characterized by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscope (SEM). The results show that the as-deposited CrN and Cr-Mo-N coatings all exhibit B1 face-centered cubic (fcc) phase based on the CrN lattice. Mo ions substitute for Cr ions in Cr-N lattice, forming the solid solution Cr-Mo-N coatings. At 600 °C, XRD and Raman spectra show that the MoO3 phase forms in Cr-Mo-N coatings with higher Mo contents, indicating a coarser surface with higher oxygen content. At 700 °C, the cross sectional morphology of the CrN coating exhibits loose columnar grains with some porous regions due to the internal stress while the Cr-Mo-N coating shows the dense columnar structure. This study reveals that the Cr-Mo-N coatings with lower Mo contents (<17at%) have better oxidation resistance than the CrN coating does.
Li Yuanyuan
,
Zhang Ziyi
,
Guan Jiahao
,
Li Li
,
Li Shuli
,
Cheng Zhen
,
Yang Rui
,
Zhang Yunzhe
,
Zhao Xiaoxia
,
Xu Kewei
2021, 50(5):1513-1517.
DOI: 10.12442/j.issn.1002-185X.20200253
Abstract:
A series of SnO2 thin films doped with low-dose Al (≤1mol%) were prepared on slide glass substrates by radio frequency (RF) magnetron sputtering. The crystal structure and optical properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-IR spectrometer, and photoluminescence (PL) measurements. Results show that the lattice constant c decreases with increasing the Al content, which implies that Al atoms are successfully introduced into the SnO2 and occupy the Sn sites, and large number of oxygen vacancies are generated. The average transmittance values are higher than 88% within the visible spectral region (400~800 nm) for all the films. The bandgap broadens when the Al percentage increases, which is dominated by the Burstein-Moss (BM) effect. The PL spectra of these films have near band edge and deep level emission under the radiation excitation of 265 nm wavelength. The observed intensity of these peaks increases consistently with increasing the Al percentage.
A series of SnO2 thin films doped with low-dose Al (≤1mol%) were prepared on slide glass substrates by radio frequency (RF) magnetron sputtering. The crystal structure and optical properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-IR spectrometer, and photoluminescence (PL) measurements. Results show that the lattice constant c decreases with increasing the Al content, which implies that Al atoms are successfully introduced into the SnO2 and occupy the Sn sites, and large number of oxygen vacancies are generated. The average transmittance values are higher than 88% within the visible spectral region (400~800 nm) for all the films. The bandgap broadens when the Al percentage increases, which is dominated by the Burstein-Moss (BM) effect. The PL spectra of these films have near band edge and deep level emission under the radiation excitation of 265 nm wavelength. The observed intensity of these peaks increases consistently with increasing the Al percentage.
2021, 50(5):1518-1522.
DOI: 10.12442/j.issn.1002-185X.20200260
Abstract:
The epitaxial SmxNd1-xNiO3 (x=0.5, 0.55, 0.6, SNNO) thin films with (001)-oriented single-crystal LaAlO3 substrates were fabricated by a chemical solution deposition technique, namely polymer-assisted deposition (PAD) under the ambient oxygen annealing. X-ray diffraction θ-2θ scan, rocking curve measurement, φ-scan and scanning electron microscopy were used to study the SNNO characteristics. The results reveal the good crystallinity and heteroepitaxy of these SNNO films. Temperature dependence of the resistivity indicates that all the films show a clear Mott metal-insulator transition (MIT) and the transition temperature (TMI) shifts to higher temperature with the increase of Sm content. The epitaxial Sm0.55Nd0.45NiO3 thin films exhibit MIT near room temperature. The successful growth of high quality SNNO films with room temperature transition by economic and facile PAD method shows great potential in practical application of nickelate.
The epitaxial SmxNd1-xNiO3 (x=0.5, 0.55, 0.6, SNNO) thin films with (001)-oriented single-crystal LaAlO3 substrates were fabricated by a chemical solution deposition technique, namely polymer-assisted deposition (PAD) under the ambient oxygen annealing. X-ray diffraction θ-2θ scan, rocking curve measurement, φ-scan and scanning electron microscopy were used to study the SNNO characteristics. The results reveal the good crystallinity and heteroepitaxy of these SNNO films. Temperature dependence of the resistivity indicates that all the films show a clear Mott metal-insulator transition (MIT) and the transition temperature (TMI) shifts to higher temperature with the increase of Sm content. The epitaxial Sm0.55Nd0.45NiO3 thin films exhibit MIT near room temperature. The successful growth of high quality SNNO films with room temperature transition by economic and facile PAD method shows great potential in practical application of nickelate.
2021, 50(5):1523-1530.
DOI: 10.12442/j.issn.1002-185X.20200302
Abstract:
The duplex CrON coatings were prepared on H13 tool steels by combination of plasma nitriding and arc ion plating. The effects of oxygen flow rate on microstructure and corrosion behavior of duplex CrON coating in the molten aluminum were investigated. Results show that the as-deposited coatings with oxygen flow rate of 0, 50, and 100 mL/min, namely CrON-0, CrON-50, and CrON-100 coatings, mainly consist of B1-CrN phase. The major components of CrON coating change from nitride into oxide phase with increasing the oxygen flow rate, and the Cr2O3 crystalline phase is obviously observed in the as-deposited coatings with oxygen flow rate of 200 mL/min, namely CrON-200 coating. Oxygen addition in nitride restrains the columnar growth of grains resulting in the dense microstructure. The surface defects and roughness increase with the increase of oxygen content. The failure behavior of duplex CrON coatings is mainly corrosion pitting in molten aluminium. The CrON-50 coating reveals the best corrosion resistance due to the dense columnar microstructure and high thermal stability. The dense Cr2O3 layer in CrON-200 coating is also favourable for corrosion protection against the molten aluminum.
The duplex CrON coatings were prepared on H13 tool steels by combination of plasma nitriding and arc ion plating. The effects of oxygen flow rate on microstructure and corrosion behavior of duplex CrON coating in the molten aluminum were investigated. Results show that the as-deposited coatings with oxygen flow rate of 0, 50, and 100 mL/min, namely CrON-0, CrON-50, and CrON-100 coatings, mainly consist of B1-CrN phase. The major components of CrON coating change from nitride into oxide phase with increasing the oxygen flow rate, and the Cr2O3 crystalline phase is obviously observed in the as-deposited coatings with oxygen flow rate of 200 mL/min, namely CrON-200 coating. Oxygen addition in nitride restrains the columnar growth of grains resulting in the dense microstructure. The surface defects and roughness increase with the increase of oxygen content. The failure behavior of duplex CrON coatings is mainly corrosion pitting in molten aluminium. The CrON-50 coating reveals the best corrosion resistance due to the dense columnar microstructure and high thermal stability. The dense Cr2O3 layer in CrON-200 coating is also favourable for corrosion protection against the molten aluminum.
2021, 50(5):1531-1541.
DOI: 10.12442/j.issn.1002-185X.20200939
Abstract:
To enhance the surface protection of the bimodal Mo-Si-B alloy and simultaneously maintain its superior mechanical properties, a multilayered coating (MoSi2, Mo5Si3 and Mo5SiB2/MoB) was synthesized on its surface via pack cementation. Results show that, compared to the coating on the fine-grained substrate, the coating surface on the bimodal substrate is rougher and exhibits bimodal microstructure. Additionally, the fracture toughness of bimodal alloy after coating is acceptable. The distributed La2O3 particles toughen the coating. Besides, the coated bimodal specimens show excellent oxidation resistance at 1100~1300 °C, which is attributed to the quick formation of a thin and self-healing SiO2-B2O3 film on the coating surface. With increasing the temperature, the thickness of SiO2-B2O3 film and the oxidation product Mo5Si3 increase because the viscosity of SiO2-B2O3 film decreases. Also, improving temperature promotes the interdiffusion of Si and B, accelerating the growth of Mo5Si3 and Mo5SiB2/MoB layers. Compared to the coated bimodal alloy, the coated fine-grained alloy exhibits more oxidation mass gain at 1300 °C since the unimodal MoSi2 coating has more grain boundaries.
To enhance the surface protection of the bimodal Mo-Si-B alloy and simultaneously maintain its superior mechanical properties, a multilayered coating (MoSi2, Mo5Si3 and Mo5SiB2/MoB) was synthesized on its surface via pack cementation. Results show that, compared to the coating on the fine-grained substrate, the coating surface on the bimodal substrate is rougher and exhibits bimodal microstructure. Additionally, the fracture toughness of bimodal alloy after coating is acceptable. The distributed La2O3 particles toughen the coating. Besides, the coated bimodal specimens show excellent oxidation resistance at 1100~1300 °C, which is attributed to the quick formation of a thin and self-healing SiO2-B2O3 film on the coating surface. With increasing the temperature, the thickness of SiO2-B2O3 film and the oxidation product Mo5Si3 increase because the viscosity of SiO2-B2O3 film decreases. Also, improving temperature promotes the interdiffusion of Si and B, accelerating the growth of Mo5Si3 and Mo5SiB2/MoB layers. Compared to the coated bimodal alloy, the coated fine-grained alloy exhibits more oxidation mass gain at 1300 °C since the unimodal MoSi2 coating has more grain boundaries.
2021, 50(5):1542-1548.
DOI: 10.12442/j.issn.1002-185X.E20200015
Abstract:
To elevate the wear resistance of TC4 alloy, Co30Cr8W1.6C3Ni1.4Si coating was fabricated on the surface by laser thermal spraying (LTS). The morphologies and phases of obtained coatings were analyzed by scanning electronic microscope (SEM) and X-ray diffraction (XRD), respectively. The friction and wear properties of the coatings in poly-alpha-olefin (PAO)+2.5wt% molybdenum dithiocarbamate (MoDTC) oil were investigated by wear tester. The results show that the laser thermal sprayed Co30Cr8W1.6C3Ni1.4Si coatings are primarily composed of Ti, WC1-x, CoO, Co2Ti4O and CoAl phases, and the metallurgical bonding forms at the coating interface. The average coefficient of friction (COF) of Co30Cr8W1.6C3Ni1.4Si coatings fabricated at the laser power of 1000, 1200 and 1400 W is 0.151, 0.120, and 0.171 with corresponding wear rate of 1.17×10-6, 1.33×10-6 and 2.80×10-6 mm3·N-1·m-1, respectively, which increases with the increase of laser power. The wear mechanism is abrasive wear, and the dendrite size is the dominant role of anti-wear.
To elevate the wear resistance of TC4 alloy, Co30Cr8W1.6C3Ni1.4Si coating was fabricated on the surface by laser thermal spraying (LTS). The morphologies and phases of obtained coatings were analyzed by scanning electronic microscope (SEM) and X-ray diffraction (XRD), respectively. The friction and wear properties of the coatings in poly-alpha-olefin (PAO)+2.5wt% molybdenum dithiocarbamate (MoDTC) oil were investigated by wear tester. The results show that the laser thermal sprayed Co30Cr8W1.6C3Ni1.4Si coatings are primarily composed of Ti, WC1-x, CoO, Co2Ti4O and CoAl phases, and the metallurgical bonding forms at the coating interface. The average coefficient of friction (COF) of Co30Cr8W1.6C3Ni1.4Si coatings fabricated at the laser power of 1000, 1200 and 1400 W is 0.151, 0.120, and 0.171 with corresponding wear rate of 1.17×10-6, 1.33×10-6 and 2.80×10-6 mm3·N-1·m-1, respectively, which increases with the increase of laser power. The wear mechanism is abrasive wear, and the dendrite size is the dominant role of anti-wear.
Liu Mingxia
,
Zhang Wenkang
,
Chang Gengrong
,
Zhang Xiaohua
,
Wang Dong
,
He Binfeng
,
Fu Fuxing
,
Meng Yu
,
Ma Fei
,
Xu Kewei
2021, 50(5):1549-1555.
DOI: 10.12442/j.issn.1002-185X.20200030
Abstract:
Shot peening treatment was adopted to strengthen the steel surface, and the influence of the temperature field on the residual stress and fatigue resistance of the 17-4PH stainless steel was investigated. Firstly, the microstructure analysis by scanning electron microscope (SEM) and the nondestructive testing by X-ray technology were carried out to evaluate the residual stress of 17-4PH steel after shot peening treatments at room temperature. Fatigue property tests were conducted on the rotary bending fatigue tester and the related properties were presented through S-N curve. Then, by adopting the optimum shot peening treatment, the fatigue resistance and residual stress relaxation on the shot-peened surface were studied at 150, 300 and 450 °C. The results demonstrate that the low intensity shot peening parameters are the optimized ones for 17-4PH stainless steel at room temperature. Meanwhile, the shot peening treatment can significantly improve the fatigue life of 17-4PH steel at the environment temperature T<300 °C. However, the fatigue properties of 17-4PH steel decrease significantly at T>450 °C. When the shot-peened 17-4PH steel is applied at high temperature, the serious residual stress relaxation and the reduced surface integrity become the predominant effects for the reduced fatigue resistance. The results provide experimental basis for the application of shot peening treatment in special industrial fields, such as steam turbine industry.
Shot peening treatment was adopted to strengthen the steel surface, and the influence of the temperature field on the residual stress and fatigue resistance of the 17-4PH stainless steel was investigated. Firstly, the microstructure analysis by scanning electron microscope (SEM) and the nondestructive testing by X-ray technology were carried out to evaluate the residual stress of 17-4PH steel after shot peening treatments at room temperature. Fatigue property tests were conducted on the rotary bending fatigue tester and the related properties were presented through S-N curve. Then, by adopting the optimum shot peening treatment, the fatigue resistance and residual stress relaxation on the shot-peened surface were studied at 150, 300 and 450 °C. The results demonstrate that the low intensity shot peening parameters are the optimized ones for 17-4PH stainless steel at room temperature. Meanwhile, the shot peening treatment can significantly improve the fatigue life of 17-4PH steel at the environment temperature T<300 °C. However, the fatigue properties of 17-4PH steel decrease significantly at T>450 °C. When the shot-peened 17-4PH steel is applied at high temperature, the serious residual stress relaxation and the reduced surface integrity become the predominant effects for the reduced fatigue resistance. The results provide experimental basis for the application of shot peening treatment in special industrial fields, such as steam turbine industry.
2021, 50(5):1556-1562.
DOI: 10.12442/j.issn.1002-185X.20200091
Abstract:
By advanced analytical transmission electron microscope, an unexpected interdiffusion between magnetron sputtered Fe-Co thin film and Al2O3 substrate was detected and systematically investigated in this study. Results show that a new phase of spinel FeAl2O4 forms, leading to the formation of interfacial layer. Detailed microstructure characterization reveals the interdiffusion associated with incommensurate structure formation near the interface in the Fe-Co thin film. The interdiffusion and accompanied new phase formation between the Fe-Co thin film and sapphire substrate are detected, and the associated microstructure evolution at the interfacial region is discussed, which may considerably influence the thin film magnetic properties.
By advanced analytical transmission electron microscope, an unexpected interdiffusion between magnetron sputtered Fe-Co thin film and Al2O3 substrate was detected and systematically investigated in this study. Results show that a new phase of spinel FeAl2O4 forms, leading to the formation of interfacial layer. Detailed microstructure characterization reveals the interdiffusion associated with incommensurate structure formation near the interface in the Fe-Co thin film. The interdiffusion and accompanied new phase formation between the Fe-Co thin film and sapphire substrate are detected, and the associated microstructure evolution at the interfacial region is discussed, which may considerably influence the thin film magnetic properties.
2021, 50(5):1563-1568.
DOI: 10.12442/j.issn.1002-185X.20200285
Abstract:
In-situ magnesium silicide/aluminum (Mg2Si/Al) composites were fabricated by laser deposition. A dynamic model of in-situ Mg2Si/Al composites was established. The laser power (system temperature), Mg-rich layer thickness, Si particle size, and Al content were identified as the main factors affecting the reaction rate and degree. Results show that increasing the laser power (system temperature) and reducing the Mg-rich layer thickness, Si particle size, and Al content accelerate the reaction rate and degree.
In-situ magnesium silicide/aluminum (Mg2Si/Al) composites were fabricated by laser deposition. A dynamic model of in-situ Mg2Si/Al composites was established. The laser power (system temperature), Mg-rich layer thickness, Si particle size, and Al content were identified as the main factors affecting the reaction rate and degree. Results show that increasing the laser power (system temperature) and reducing the Mg-rich layer thickness, Si particle size, and Al content accelerate the reaction rate and degree.
2021, 50(5):1569-1575.
DOI: 10.12442/j.issn.1002-185X.20191073
Abstract:
The Ir(111)/SiC(111) interfaces were investigated by first-principles study based on density functional theory (DFT). Considering different stacking sites and terminations, six different interfaces were studied. The results show that an Ir(111) slab with 9 atom layers exhibits bulk-like interior characteristic, while a 12-atom-layer SiC(111) slab represents the properties of bulk SiC. Adhesion and interfacial energy results show that the C-terminated top-site (C-TS) and Si-terminated center-site (Si-CS) interfaces are highly stable with the highest work of adhesion of 6.35 and 6.23 J/m2, and the smallest interfacial energy of 0.07 and 0.10 J/m2 after relaxation, respectively. Electronic structure analysis reveals that the C-TS interface has the ionic characteristics, while the Si-CS interface exhibits covalent bond characteristics. The bonding strength and stability of C-TS and Si-CS interfaces are attributed to the hybridization between Ir-d and C-p, Si-p orbits. Compared with the C-TS interface, sub-interfacial atoms have more interaction with Ir atoms in Si-CS interface.
The Ir(111)/SiC(111) interfaces were investigated by first-principles study based on density functional theory (DFT). Considering different stacking sites and terminations, six different interfaces were studied. The results show that an Ir(111) slab with 9 atom layers exhibits bulk-like interior characteristic, while a 12-atom-layer SiC(111) slab represents the properties of bulk SiC. Adhesion and interfacial energy results show that the C-terminated top-site (C-TS) and Si-terminated center-site (Si-CS) interfaces are highly stable with the highest work of adhesion of 6.35 and 6.23 J/m2, and the smallest interfacial energy of 0.07 and 0.10 J/m2 after relaxation, respectively. Electronic structure analysis reveals that the C-TS interface has the ionic characteristics, while the Si-CS interface exhibits covalent bond characteristics. The bonding strength and stability of C-TS and Si-CS interfaces are attributed to the hybridization between Ir-d and C-p, Si-p orbits. Compared with the C-TS interface, sub-interfacial atoms have more interaction with Ir atoms in Si-CS interface.
2021, 50(5):1656-1664.
DOI: 10.12442/j.issn.1002-185X.20200378
Abstract:
The design and preparation of aluminum alloy surface protective coating is one of the main methods to improve the surface hardness and corrosion resistance of aluminum alloy components. In this paper, a SiC/TiN particle reinforced Ni-Mo nanocomposite coating was prepared on the surface of 6061 aluminum alloy by pulse electrodeposition technique. By introducing SiC and TiN nanoparticles into the coating and changing the average current density and duty cycle of electrodeposition, the microstructure of the composite coating was adjusted, the film formation process and grain refinement mechanism of the nanoparticle-enhanced coating were analyzed. The relationship between the microstructure of composite coating and the corrosion resistance and wear resistance was studied. The results showed that the addition of double nanoparticles resulted in a shift of the coating structure from conical to cellular, and the grain size was reduced from 29.86 nm to 22.79 nm. The coatings prepared at current density of 8 A·dm-2 were the most homogeneous and dense with the highest SiC/TiN particle complexes of 1.3 wt% and 3.1 wt%, respectively. The coating exhibits (111) preferred orientation and typical FCC structure, with nanoparticles uniformly dispersed in a Ni-Mo matrix. The corrosion behavior of the coatings was investigated by Tafel polarization and immersion test. Compared with the corrosion current density of Ni-Mo composite coating of 7.08 μA/cm2, Ni-Mo/SiC-TiN nanocomposite coatings prepared at current densities of 4 A·dm-2, 8 A·dm-2, 12 A·dm-2 and duty cycle of 40% and 60% was 4.68 μA/cm2, 4.12 μA/cm2, 5.75 μA/cm2, 4.37 μA/cm2 and 5.53 μA/cm2, which were reduced by 34%, 42%, 19%, 38% and 21% respectively. In particular, the nanocomposite coatings prepared at the current density of 8 A·dm-2 and the duty cycle of 20% exhibited the best corrosion resistance. Compared with Ni-Mo coating, the introduction of SiC/TiN particles significantly improves the wear resistance of the coating. In addition, the mechanism of pulsed co-deposition is discussed in this paper.
The design and preparation of aluminum alloy surface protective coating is one of the main methods to improve the surface hardness and corrosion resistance of aluminum alloy components. In this paper, a SiC/TiN particle reinforced Ni-Mo nanocomposite coating was prepared on the surface of 6061 aluminum alloy by pulse electrodeposition technique. By introducing SiC and TiN nanoparticles into the coating and changing the average current density and duty cycle of electrodeposition, the microstructure of the composite coating was adjusted, the film formation process and grain refinement mechanism of the nanoparticle-enhanced coating were analyzed. The relationship between the microstructure of composite coating and the corrosion resistance and wear resistance was studied. The results showed that the addition of double nanoparticles resulted in a shift of the coating structure from conical to cellular, and the grain size was reduced from 29.86 nm to 22.79 nm. The coatings prepared at current density of 8 A·dm-2 were the most homogeneous and dense with the highest SiC/TiN particle complexes of 1.3 wt% and 3.1 wt%, respectively. The coating exhibits (111) preferred orientation and typical FCC structure, with nanoparticles uniformly dispersed in a Ni-Mo matrix. The corrosion behavior of the coatings was investigated by Tafel polarization and immersion test. Compared with the corrosion current density of Ni-Mo composite coating of 7.08 μA/cm2, Ni-Mo/SiC-TiN nanocomposite coatings prepared at current densities of 4 A·dm-2, 8 A·dm-2, 12 A·dm-2 and duty cycle of 40% and 60% was 4.68 μA/cm2, 4.12 μA/cm2, 5.75 μA/cm2, 4.37 μA/cm2 and 5.53 μA/cm2, which were reduced by 34%, 42%, 19%, 38% and 21% respectively. In particular, the nanocomposite coatings prepared at the current density of 8 A·dm-2 and the duty cycle of 20% exhibited the best corrosion resistance. Compared with Ni-Mo coating, the introduction of SiC/TiN particles significantly improves the wear resistance of the coating. In addition, the mechanism of pulsed co-deposition is discussed in this paper.
2021, 50(5):1665-1672.
DOI: 10.12442/j.issn.1002-185X.20200372
Abstract:
A Cr coating of about 4 μm thick was successfully prepared on pure zirconium by filtered cathodic vacuum arc ion deposition technology (FCVAD), and the high-temperature oxidation properties of bare and Cr-coated Zr were measured using a thermogravimetric analyzer (TGA) in steam environment at different temperatures. Their phase composition, microstructure and composition distributions before and after the steam oxidation tests were characterized by X-ray diffraction analyzer (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). It was found that the mass gain per unit area of Cr-coated Zr was only 1/4, 1/6 and 4/9 of that of bare Zr after 3600 s exposure in 900, 1000 and 1100℃ steam environment, respectively. In the initial stage of steam oxidation, a compact and uniform Cr2O3layer was formed on the surface of Cr layer, significantly reducing oxygen or steam diffusion inwards. After Cr coating was completely oxidized into Cr2O3, Zr substrate was gradually oxidized, but the Cr2O3 at Cr2O3/Zr interface was reduced to form Cr. In addition, the oxidation activation energy of the Cr-coated Zr was up to 293.17 kJ/mol.
A Cr coating of about 4 μm thick was successfully prepared on pure zirconium by filtered cathodic vacuum arc ion deposition technology (FCVAD), and the high-temperature oxidation properties of bare and Cr-coated Zr were measured using a thermogravimetric analyzer (TGA) in steam environment at different temperatures. Their phase composition, microstructure and composition distributions before and after the steam oxidation tests were characterized by X-ray diffraction analyzer (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). It was found that the mass gain per unit area of Cr-coated Zr was only 1/4, 1/6 and 4/9 of that of bare Zr after 3600 s exposure in 900, 1000 and 1100℃ steam environment, respectively. In the initial stage of steam oxidation, a compact and uniform Cr2O3layer was formed on the surface of Cr layer, significantly reducing oxygen or steam diffusion inwards. After Cr coating was completely oxidized into Cr2O3, Zr substrate was gradually oxidized, but the Cr2O3 at Cr2O3/Zr interface was reduced to form Cr. In addition, the oxidation activation energy of the Cr-coated Zr was up to 293.17 kJ/mol.
2021, 50(5):1673-1678.
DOI: 10.12442/j.issn.1002-185X.20200095
Abstract:
SiC coated C/SiC and C/SiBCN composites were prepared by chemical vapor deposition (CVD) combined with polymer infiltration and pyrolysis (PIP) techniques. The effects of thermal cycling on bending properties of these composites were studied. Compared with SiC-C/SiC, the average bending strength of SiC-C/SiBCN was measured as around 605 MPa at room temperature, which increased by 126.6 %. After the oxidation at 1000 °C and 1200 °C for 3 cycles, the residual bending strength of SiC-C/SiBCN was separately measured as 417 and 342 MPa. The corresponding strength retention rates at 1000 °C and 1200 °C were 68.9 % and 56.5 %, respectively. Compared to the SiC ceramic matrix by PIP, the porosity of SiBCN ceramic matrix was lower. Meanwhile, SiO2 and B2O3 were formed during the oxidation of SiBCN, which could decrease permeation ration of the oxygen. Thus, the oxidation resistance and strength retention rate of SiC-C/SiBCN were significantly better than SiC-C/SiC composite.
SiC coated C/SiC and C/SiBCN composites were prepared by chemical vapor deposition (CVD) combined with polymer infiltration and pyrolysis (PIP) techniques. The effects of thermal cycling on bending properties of these composites were studied. Compared with SiC-C/SiC, the average bending strength of SiC-C/SiBCN was measured as around 605 MPa at room temperature, which increased by 126.6 %. After the oxidation at 1000 °C and 1200 °C for 3 cycles, the residual bending strength of SiC-C/SiBCN was separately measured as 417 and 342 MPa. The corresponding strength retention rates at 1000 °C and 1200 °C were 68.9 % and 56.5 %, respectively. Compared to the SiC ceramic matrix by PIP, the porosity of SiBCN ceramic matrix was lower. Meanwhile, SiO2 and B2O3 were formed during the oxidation of SiBCN, which could decrease permeation ration of the oxygen. Thus, the oxidation resistance and strength retention rate of SiC-C/SiBCN were significantly better than SiC-C/SiC composite.
2021, 50(5):1679-1684.
DOI: 10.12442/j.issn.1002-185X.20200127
Abstract:
RuO2-based thick film resistor is widely used in thick film integrated circuits because of its good resistance stability and low temperature coefficient of resistance. In this study, the ASf/SiO2 composite and alumina ceramic were chosen as substrates, and the RuO2-based thick films were fabricated on the two substrates by screen printing. The thermal mismatch between the thick film and substrates from 25℃ to 700℃ was analyzed by using the digital image correlation method, finite element method and XRD stress measurement method, and then the resistance-temperature characteristic for thick film was investigated. The results showed that the thermal expansion coefficient of the thick film was larger than that of ASf/SiO2 composites. The thick film fabricated on ASf/SiO2 composite substrate was suffered residual tensile, which was released at highStemperature. Thus, the distance between conductive particles was reduced, leading to the decrease of potential barrier resistance. Thick film prepared on ASf/SiO2 composite substrates presented negative resistance-temperature characteristic. On the contrary, the thermal expansion coefficient of the thick film was smaller than that of alumina. The thick film fabricated on alumina substrate was suffered residual compressive stress, which was also released at highStemperature. And then, the distance between conductive particles was rose, resulting in the increase of potential barrier resistance. The thick film prepared on alumina substrate exhibited positive resistance-temperature characteristic.. Keywords: RuO2-based resistance film; ASf/SiO2 composite; thermal mismatch; residual stress
RuO2-based thick film resistor is widely used in thick film integrated circuits because of its good resistance stability and low temperature coefficient of resistance. In this study, the ASf/SiO2 composite and alumina ceramic were chosen as substrates, and the RuO2-based thick films were fabricated on the two substrates by screen printing. The thermal mismatch between the thick film and substrates from 25℃ to 700℃ was analyzed by using the digital image correlation method, finite element method and XRD stress measurement method, and then the resistance-temperature characteristic for thick film was investigated. The results showed that the thermal expansion coefficient of the thick film was larger than that of ASf/SiO2 composites. The thick film fabricated on ASf/SiO2 composite substrate was suffered residual tensile, which was released at highStemperature. Thus, the distance between conductive particles was reduced, leading to the decrease of potential barrier resistance. Thick film prepared on ASf/SiO2 composite substrates presented negative resistance-temperature characteristic. On the contrary, the thermal expansion coefficient of the thick film was smaller than that of alumina. The thick film fabricated on alumina substrate was suffered residual compressive stress, which was also released at highStemperature. And then, the distance between conductive particles was rose, resulting in the increase of potential barrier resistance. The thick film prepared on alumina substrate exhibited positive resistance-temperature characteristic.. Keywords: RuO2-based resistance film; ASf/SiO2 composite; thermal mismatch; residual stress
2021, 50(5):1685-1693.
DOI: 10.12442/j.issn.1002-185X.20200387
Abstract:
To break through the technical bottleneck of low bonding strength of thermal protective coatings prepared by plasma spraying on aluminum alloy surfaces, a three-cathode plasma spraying system was used to prepare 8YSZ thermal protective coatings on the surface of 7A04-T6 ultra high strength aluminum alloy. With the help of scanning electron microscope, X-ray diffractometer, microhardness tester and universal testing machine, the effects of different gas flow parameters on the micromorphology, phase composition, microhardness and bonding strength of the coatings were analyzed and characterized. Finally, the critical value of the influence of gas flow parameters on the bonding strength of the coating was proposed. The results showed that the upper surface of the coatings prepared under different gas flow parameters all had molten and semi- molten powder particle morphology, pore structure and crack propagation morphology. With the increase of gas flow, the density of the coating increased, and the tamped morphology of the coating showed a trend of increasing first and then decreasing. The phase structure of the coating prepared under different gas flow parameters was basically consistent with the feed powder, and there was only a single component of Zr0.92Y0.08O1.96. With the increase of gas flow parameters, the average microhardness of the coating showed a gradually increasing trend. With the increase of gas flow parameters, the average bonding strength of the coating showed a trend of increasing first and then decreasing.
To break through the technical bottleneck of low bonding strength of thermal protective coatings prepared by plasma spraying on aluminum alloy surfaces, a three-cathode plasma spraying system was used to prepare 8YSZ thermal protective coatings on the surface of 7A04-T6 ultra high strength aluminum alloy. With the help of scanning electron microscope, X-ray diffractometer, microhardness tester and universal testing machine, the effects of different gas flow parameters on the micromorphology, phase composition, microhardness and bonding strength of the coatings were analyzed and characterized. Finally, the critical value of the influence of gas flow parameters on the bonding strength of the coating was proposed. The results showed that the upper surface of the coatings prepared under different gas flow parameters all had molten and semi- molten powder particle morphology, pore structure and crack propagation morphology. With the increase of gas flow, the density of the coating increased, and the tamped morphology of the coating showed a trend of increasing first and then decreasing. The phase structure of the coating prepared under different gas flow parameters was basically consistent with the feed powder, and there was only a single component of Zr0.92Y0.08O1.96. With the increase of gas flow parameters, the average microhardness of the coating showed a gradually increasing trend. With the increase of gas flow parameters, the average bonding strength of the coating showed a trend of increasing first and then decreasing.
Luo Guoqiang
,
Wang Chunsheng
,
Hu Jianian
,
Chen Changlian
,
Sun Yi
,
Li Meijuan
,
Wang Chuanbin
,
Shen Qiang
2021, 50(5):1694-1698.
DOI: 10.12442/j.issn.1002-185X.20200133
Abstract:
In this paper, silver films for electromagnetic induction heating were prepared on alumina ceramic through screen printing and pressureless sintering. The microstructure, mechanical properties and electrical properties of the silver films were characterized by SEM, four probe test and tensile test. The results indicate that the density of silver film is closely related to sintering temperature and glass frit content. With the increase of sintering temperature, the viscosity of the glass melt decreases, the silver particles are wetted and rearranged effectively, and a dense silver network forms through the sintering neck growth and further fusion. Meanwhile, with the increase of glass frit content, glass melt can not only promote the densification of silver particles, but also improve the adhesion strength of silver film and substrate. However, much glass melts block the contact between silver particles, thereby reducing the conductivity of the silver film. When the sintering temperature is 640 ℃ and the content of glass frit is 4 wt.%, the silver film owns good comprehensive properties. The sheet resistance reaches a minimum value of 2.26 mΩ/□, and the adhesion strength is high, reaching 14.64 MPa. The experimental results of electromagnetic induction heating show that the silver film with smaller sheet resistance has a faster heating rate.
In this paper, silver films for electromagnetic induction heating were prepared on alumina ceramic through screen printing and pressureless sintering. The microstructure, mechanical properties and electrical properties of the silver films were characterized by SEM, four probe test and tensile test. The results indicate that the density of silver film is closely related to sintering temperature and glass frit content. With the increase of sintering temperature, the viscosity of the glass melt decreases, the silver particles are wetted and rearranged effectively, and a dense silver network forms through the sintering neck growth and further fusion. Meanwhile, with the increase of glass frit content, glass melt can not only promote the densification of silver particles, but also improve the adhesion strength of silver film and substrate. However, much glass melts block the contact between silver particles, thereby reducing the conductivity of the silver film. When the sintering temperature is 640 ℃ and the content of glass frit is 4 wt.%, the silver film owns good comprehensive properties. The sheet resistance reaches a minimum value of 2.26 mΩ/□, and the adhesion strength is high, reaching 14.64 MPa. The experimental results of electromagnetic induction heating show that the silver film with smaller sheet resistance has a faster heating rate.
2021, 50(5):1699-1705.
DOI: 10.12442/j.issn.1002-185X.20200184
Abstract:
Traditional YSZ coating and Eu3+ doped YSZ coating were prepared by APS method. SEM was used to observe and measure the morphology and porosity level of the two coatings. The thermal conductivity of the two coatings in the range of 100-1100°C was measured by using a flashlight heat conducting system. 30 cycles and 50 cycles of oxidation cycle treatment for both YSZ coating and YSZ:Eu coating were conducted by oxidation cycle test equipment at 1100°C, the interfacial fracture toughness of as-received and heat treated specimens were then calculated. The results show that the thermal conductivity of the YSZ:Eu coating is lower than that of the YSZ coating at the same temperature, indicating that 2mol% Eu3+ doping can effectively reduce the thermal conductivity of the YSZ TBCs. For both types of coating, interfacial fracture toughness decreases while the TGO thickness increases with the oxidation cycle number increasing. At the same heat treatment conditions, the interfacial fracture toughness of the YSZ:Eu coating is greater than that of the YSZ coating, and the TGO thickness is thinner, indicating that 2mol% Eu3+ doping inhibits the growth of TGO and improves the coating’s interfacial properties.
Traditional YSZ coating and Eu3+ doped YSZ coating were prepared by APS method. SEM was used to observe and measure the morphology and porosity level of the two coatings. The thermal conductivity of the two coatings in the range of 100-1100°C was measured by using a flashlight heat conducting system. 30 cycles and 50 cycles of oxidation cycle treatment for both YSZ coating and YSZ:Eu coating were conducted by oxidation cycle test equipment at 1100°C, the interfacial fracture toughness of as-received and heat treated specimens were then calculated. The results show that the thermal conductivity of the YSZ:Eu coating is lower than that of the YSZ coating at the same temperature, indicating that 2mol% Eu3+ doping can effectively reduce the thermal conductivity of the YSZ TBCs. For both types of coating, interfacial fracture toughness decreases while the TGO thickness increases with the oxidation cycle number increasing. At the same heat treatment conditions, the interfacial fracture toughness of the YSZ:Eu coating is greater than that of the YSZ coating, and the TGO thickness is thinner, indicating that 2mol% Eu3+ doping inhibits the growth of TGO and improves the coating’s interfacial properties.
2021, 50(5):1706-1712.
DOI: 10.12442/j.issn.1002-185X.20200244
Abstract:
Chromized coatings were fabricated using a conventional pack-cementation method. Effect of chromizing time, as well as natural ageing on the structure and performance was investigated. The phases and microstructure were characterized by scanning electron microscopy (SEM) with EDS and X-ray diffraction (XRD). The microhardness of the surface, the nanohardness of cross-section, the adhesion strength of the coatings were characterized by Vickers microhardness tester, nano-indenter and Rockwell-C tester. The results show that the chromized coatings were composed of Cr2N, (Cr,Fe)23C6 and (Cr,Fe)7C3. In the top surface, the discontinous Cr2N crystal grains distributed in the loose chromium carbides. The Cr2N crystal grains growth larger as the chromizing time increased. In the sublayer, the phase was composed of chromium carbides. The gradient structure was formed in the chromized coatings with Cr content decreased from surface to substrate and the contrary trend for Fe content. The microhardness of the surface was between 1492HV0.05~1698HV0.05 and it decreased slightly after 1 year natural ageing. The nanohardness reduced with Cr content decreasing in cross-section of chromized coatings. The Rockwell-C test results show that there were some radial cracks and spalls around the indentation crater. However, only radial cracks were presented around the indentation craters after 1 year natural ageing, indicated the improvement of adhesion strength of the coatings to substrate.
Chromized coatings were fabricated using a conventional pack-cementation method. Effect of chromizing time, as well as natural ageing on the structure and performance was investigated. The phases and microstructure were characterized by scanning electron microscopy (SEM) with EDS and X-ray diffraction (XRD). The microhardness of the surface, the nanohardness of cross-section, the adhesion strength of the coatings were characterized by Vickers microhardness tester, nano-indenter and Rockwell-C tester. The results show that the chromized coatings were composed of Cr2N, (Cr,Fe)23C6 and (Cr,Fe)7C3. In the top surface, the discontinous Cr2N crystal grains distributed in the loose chromium carbides. The Cr2N crystal grains growth larger as the chromizing time increased. In the sublayer, the phase was composed of chromium carbides. The gradient structure was formed in the chromized coatings with Cr content decreased from surface to substrate and the contrary trend for Fe content. The microhardness of the surface was between 1492HV0.05~1698HV0.05 and it decreased slightly after 1 year natural ageing. The nanohardness reduced with Cr content decreasing in cross-section of chromized coatings. The Rockwell-C test results show that there were some radial cracks and spalls around the indentation crater. However, only radial cracks were presented around the indentation craters after 1 year natural ageing, indicated the improvement of adhesion strength of the coatings to substrate.
2021, 50(5):1713-1719.
DOI: 10.12442/j.issn.1002-185X.20200262
Abstract:
AM60B magnesium alloys were processed in sodium silicate based electrolytes by micro-arc oxidation (MAO), and the influence of the concentration ratio of potassium fluoride to sodium silicate (in short as fluoride-silicate ratio) on the microstructure and corrosion resistance of the coatings was quantitatively analyzed with changing the concentrations of KF and Na2SiO3 in the electrolyte. The results show that the main salt Na2SiO3 is essential in the film-forming reaction. When fluoride-silicate ratio was greater than zero, the film-forming reaction was intensified with the increasing of fluoride-silicate ratio, which caused the coatings owning more surface porosity, more number of large pore (> 3μm ), and larger thickness. And newly formed MgF2 and more Mg2SiO4 in the coatings because of the existence of the F- in the electrolyte will contribute to the improvement of the coatings’ anti-corrosion ability. In addition, the competitive and synergistic effect of F- and SiO32- in the electrolyte will vary with the changing of fluoride-silicate ratio, thus affecting the microstructure, phase content, and even the corrosion resistance of the coatings. In this paper, the best fluoride-silicate ratio was 0.5(KF: Na2SiO3 = 7.5:15), since the resulting coating has shown a larger thickness, better density and fewer defects due to the good synergism between F- and SiO32-. That is to say, both large thickness and excellent corrosion resistance of the coating has been obtained at this point.
AM60B magnesium alloys were processed in sodium silicate based electrolytes by micro-arc oxidation (MAO), and the influence of the concentration ratio of potassium fluoride to sodium silicate (in short as fluoride-silicate ratio) on the microstructure and corrosion resistance of the coatings was quantitatively analyzed with changing the concentrations of KF and Na2SiO3 in the electrolyte. The results show that the main salt Na2SiO3 is essential in the film-forming reaction. When fluoride-silicate ratio was greater than zero, the film-forming reaction was intensified with the increasing of fluoride-silicate ratio, which caused the coatings owning more surface porosity, more number of large pore (> 3μm ), and larger thickness. And newly formed MgF2 and more Mg2SiO4 in the coatings because of the existence of the F- in the electrolyte will contribute to the improvement of the coatings’ anti-corrosion ability. In addition, the competitive and synergistic effect of F- and SiO32- in the electrolyte will vary with the changing of fluoride-silicate ratio, thus affecting the microstructure, phase content, and even the corrosion resistance of the coatings. In this paper, the best fluoride-silicate ratio was 0.5(KF: Na2SiO3 = 7.5:15), since the resulting coating has shown a larger thickness, better density and fewer defects due to the good synergism between F- and SiO32-. That is to say, both large thickness and excellent corrosion resistance of the coating has been obtained at this point.
2021, 50(5):1720-1726.
DOI: 10.12442/j.issn.1002-185X.20200294
Abstract:
In this study, a method of cold-spray-assisted synthesis of high-aluminum bronze alloy coating is proposed, and a high-aluminum bronze coating is prepared on 45 steel matrix. The corrosion resistance of the alloy coating was measured with the CHI660D electrochemical test system by analyzing the micromorphology and phase tissue of the coating by SEM, EDS and XRD. The results show that after induction remelting, the in situ synthesis tissue of cold spray metal mixed coating is a high aluminum bronze alloy coating of beta-phase, alpha-phase, gamma-2-phase and k-phase, with dense coating and low porosity. The high aluminum bronze alloy coating in situ has good mechanical properties and wear resistance, corrosion resistance, and the performance of cast block high aluminum bronze alloy is close. The hardness of the coating is 357.0HV and the dry friction coefficient with alumina is 0.320. The stable voltages in 3.5wt.%NaCl and 5.0wt.%H2SO4 corrosion media were -366mV and -387mV, respectively.
In this study, a method of cold-spray-assisted synthesis of high-aluminum bronze alloy coating is proposed, and a high-aluminum bronze coating is prepared on 45 steel matrix. The corrosion resistance of the alloy coating was measured with the CHI660D electrochemical test system by analyzing the micromorphology and phase tissue of the coating by SEM, EDS and XRD. The results show that after induction remelting, the in situ synthesis tissue of cold spray metal mixed coating is a high aluminum bronze alloy coating of beta-phase, alpha-phase, gamma-2-phase and k-phase, with dense coating and low porosity. The high aluminum bronze alloy coating in situ has good mechanical properties and wear resistance, corrosion resistance, and the performance of cast block high aluminum bronze alloy is close. The hardness of the coating is 357.0HV and the dry friction coefficient with alumina is 0.320. The stable voltages in 3.5wt.%NaCl and 5.0wt.%H2SO4 corrosion media were -366mV and -387mV, respectively.
2021, 50(5):1727-1734.
DOI: 10.12442/j.issn.1002-185X.20200281
Abstract:
Nitride coatings have been applied and regarded as key erosion resistant coating system for aircraft compressor. In order to consider the effect of thermophysical and chemical environment as well as stress environment, it was important to study the coupling behavior of corrosion and erosion for these nitride coatings. In this work, the erosion behaviors of original coating, the hot corrosion coating and the salt spray corrosion coating were compared for both TiN/Ti coating and TiN/ZrN coating. For TiN/Ti coating, the pittings caused by coating defects were weak regions to erosion. The salt spray TiN/Ti coating had lower adhesion and erosion resistance than original coating and hot corroded coating. For TiN/ZrN coating, loose corrosion and oxide products formed on the surface of droplets during hot corrosion, so they were more easier to fall off during erosion. Moreover, the generative interlayer thermal stress in hot corrosion process weakened the adhesion between the coating and substrate. The surface of the hot corrosion coating showed the most severe spiral peeling after erosion, and the hot corroded TiN/ZrN coating had lower adhesion and erosion resistance than original coating and salt spray corroded coating.
Nitride coatings have been applied and regarded as key erosion resistant coating system for aircraft compressor. In order to consider the effect of thermophysical and chemical environment as well as stress environment, it was important to study the coupling behavior of corrosion and erosion for these nitride coatings. In this work, the erosion behaviors of original coating, the hot corrosion coating and the salt spray corrosion coating were compared for both TiN/Ti coating and TiN/ZrN coating. For TiN/Ti coating, the pittings caused by coating defects were weak regions to erosion. The salt spray TiN/Ti coating had lower adhesion and erosion resistance than original coating and hot corroded coating. For TiN/ZrN coating, loose corrosion and oxide products formed on the surface of droplets during hot corrosion, so they were more easier to fall off during erosion. Moreover, the generative interlayer thermal stress in hot corrosion process weakened the adhesion between the coating and substrate. The surface of the hot corrosion coating showed the most severe spiral peeling after erosion, and the hot corroded TiN/ZrN coating had lower adhesion and erosion resistance than original coating and salt spray corroded coating.
2021, 50(5):1735-1742.
DOI: 10.12442/j.issn.1002-185X.20200317
Abstract:
In order to obtain more excellent and comprehensive composite coatings, Ni-Co-graphene composite coatings of different graphene particle sizes were prepared by using composite electrodeposition technology, and Ni-Co alloy coatings were prepared. The surface morphology, phase structure, microhardness, wear resistance and corrosion resistance of the coating were tested. The results showed that graphene was well embedded in the coating matrix during electrodeposition, and the presence of graphene did not change the crystal structure of the coating matrix. The addition of graphene increased the microhardness of the composite coating up to 805HV. The friction coefficient of composite coating is reduced, and the adhesive wear area is reduced to some extent. The self-corrosion current density of composite coating can be reduced to 1.0905×10-5A/cm2, which is lower than that of Ni-Co alloy coating. It was shown that the addition of graphene enhanced the hardness, wear resistance and corrosion resistance of the composite coating.
In order to obtain more excellent and comprehensive composite coatings, Ni-Co-graphene composite coatings of different graphene particle sizes were prepared by using composite electrodeposition technology, and Ni-Co alloy coatings were prepared. The surface morphology, phase structure, microhardness, wear resistance and corrosion resistance of the coating were tested. The results showed that graphene was well embedded in the coating matrix during electrodeposition, and the presence of graphene did not change the crystal structure of the coating matrix. The addition of graphene increased the microhardness of the composite coating up to 805HV. The friction coefficient of composite coating is reduced, and the adhesive wear area is reduced to some extent. The self-corrosion current density of composite coating can be reduced to 1.0905×10-5A/cm2, which is lower than that of Ni-Co alloy coating. It was shown that the addition of graphene enhanced the hardness, wear resistance and corrosion resistance of the composite coating.
2021, 50(5):1743-1752.
DOI: 10.12442/j.issn.1002-185X.20200318
Abstract:
Using solid powder embedding technique, 316H austenitic stainless steel was subjected to chemical heat treatment at 1090℃ for 0.5-15h and 750-1150℃ for 10h. The effects of different process parameters on the structure and wear resistance of the chromizing layer were studied. Optical metallurgical microscope (OM) , electron scanning microscope (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and X-ray diffractometer (XRD) and other analytical methods were used to study the influence of holding time and reaction temperature on the microstructure of the chromizing layer. Using friction and wear testing machine to study the influence of different technological parameters on the wear resistance of chromizing layer. The results show that the reaction temperature has a significant effect on the thickness of the chromizing layer. The thickness of the chromizing layer and the chromizing time are parabolic at the same chromizing termprature. The chromizing layer is mainly composed of Cr23C6, Cr2C and α-Fe-Cr solid solution. In the process of chromizing, first form a carbon chromium layer on the surface of the sample. As the reaction temperature increases or the holding time is extended, α-Fe-Cr solid solution layer will be formed under the carbon chromium compound layer, and further increase the reaction temperature and holding time ,the carbon chromium compound layer will gradually disappeare. After chromizing, the wear resistance of the sample is significantly improved. Chromizing at the same temperature, the shorter the holding time of the sample, the better the wear resistance; the same holding time, the lower the reaction temperature of the sample, the better the wear resistance.
Using solid powder embedding technique, 316H austenitic stainless steel was subjected to chemical heat treatment at 1090℃ for 0.5-15h and 750-1150℃ for 10h. The effects of different process parameters on the structure and wear resistance of the chromizing layer were studied. Optical metallurgical microscope (OM) , electron scanning microscope (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and X-ray diffractometer (XRD) and other analytical methods were used to study the influence of holding time and reaction temperature on the microstructure of the chromizing layer. Using friction and wear testing machine to study the influence of different technological parameters on the wear resistance of chromizing layer. The results show that the reaction temperature has a significant effect on the thickness of the chromizing layer. The thickness of the chromizing layer and the chromizing time are parabolic at the same chromizing termprature. The chromizing layer is mainly composed of Cr23C6, Cr2C and α-Fe-Cr solid solution. In the process of chromizing, first form a carbon chromium layer on the surface of the sample. As the reaction temperature increases or the holding time is extended, α-Fe-Cr solid solution layer will be formed under the carbon chromium compound layer, and further increase the reaction temperature and holding time ,the carbon chromium compound layer will gradually disappeare. After chromizing, the wear resistance of the sample is significantly improved. Chromizing at the same temperature, the shorter the holding time of the sample, the better the wear resistance; the same holding time, the lower the reaction temperature of the sample, the better the wear resistance.
2021, 50(5):1753-1759.
DOI: 10.12442/j.issn.1002-185X.20200329
Abstract:
In this research, tantalum was modified by two-step hydrothermal treatment, and magnesium-doped tantalum oxide nanorods with narrow rod spacing were obtained on the surface of tantalum. The morphology and microstructure of nanorods were observed with the change of the doping amount of magnesium. In the process of hydrothermal treatment, the best concentration of magnesium acetate solution was 0.05 M, and the content of Mg in tantalum oxide nanorods reached 4.25 at%, and magnesium was doped in the form of Mg2+. The roughness was measured by AFM and the roughness of Ta2O5 nanorods and Mg-Ta2O5 nanorods was higher than that of pure tantalum. ICP results showed that the precipitation rate of magnesium ions in normal saline increased greatly at first and then slowed down. Ta2O5 nanorod could not induce apatite until 12 days while apatite deposited on the surface of Mg-Ta2O5 nanorod coating for less than 8 days in biological activity test. Mg-Ta2O5 nanorod coating effectively improved the biological activity of tantalum substrate.
In this research, tantalum was modified by two-step hydrothermal treatment, and magnesium-doped tantalum oxide nanorods with narrow rod spacing were obtained on the surface of tantalum. The morphology and microstructure of nanorods were observed with the change of the doping amount of magnesium. In the process of hydrothermal treatment, the best concentration of magnesium acetate solution was 0.05 M, and the content of Mg in tantalum oxide nanorods reached 4.25 at%, and magnesium was doped in the form of Mg2+. The roughness was measured by AFM and the roughness of Ta2O5 nanorods and Mg-Ta2O5 nanorods was higher than that of pure tantalum. ICP results showed that the precipitation rate of magnesium ions in normal saline increased greatly at first and then slowed down. Ta2O5 nanorod could not induce apatite until 12 days while apatite deposited on the surface of Mg-Ta2O5 nanorod coating for less than 8 days in biological activity test. Mg-Ta2O5 nanorod coating effectively improved the biological activity of tantalum substrate.
Hu Chuanqi
,
Chen Yufeng
,
Huang Xiaoting
,
Liu Hailin
,
Gang Boren
,
Jia Zhihui
,
Huo Yanli
,
Yang Taisheng
,
Wang Hua
,
Li Hui
,
Sun Haoran
2021, 50(5):1576-1582.
DOI: 10.12442/j.issn.1002-185X.20200316
Abstract:
The effect of monofunctional monomers on the rheological and photosensitive properties of resin-based Al2O3 slurry was studied from the perspective of molecular structure and functional groups. The bifunctional group monomer 1,6-hexanediol diacrylate (HDDA) and triple functional group monomer trimethylolpropane triacrylate (TMPTA) were used as raw materials, adding monofunctional monomers X with a selected volume ratio of VHDDA:VX:VTMPTA=6:3:1. The photosensitive resin was fabricated by magnetically stirring at room temperature (RT), and the rheological properties of monofunctional monomers X and resins were studied. The resin-based alumina slurries with solid content of 30vol%~50vol% were prepared by ball milling, the 3D printing process based on stereolithography (SL) was realized and the alumina bodies were fabricated. The monofunctional monomers acryloylmorpholin (ACMO), 2-phenoxyethyl acrylate (2-PHEA), and hydroxyethyl acrylate (HEA) with hydrophilic groups and high photopolymerization activity were used, and the resins with high activity and photopolymerization accuracy were fabricated, benefiting for fabricating Al2O3 slurries with superior rheological and photosensitive properties.
The effect of monofunctional monomers on the rheological and photosensitive properties of resin-based Al2O3 slurry was studied from the perspective of molecular structure and functional groups. The bifunctional group monomer 1,6-hexanediol diacrylate (HDDA) and triple functional group monomer trimethylolpropane triacrylate (TMPTA) were used as raw materials, adding monofunctional monomers X with a selected volume ratio of VHDDA:VX:VTMPTA=6:3:1. The photosensitive resin was fabricated by magnetically stirring at room temperature (RT), and the rheological properties of monofunctional monomers X and resins were studied. The resin-based alumina slurries with solid content of 30vol%~50vol% were prepared by ball milling, the 3D printing process based on stereolithography (SL) was realized and the alumina bodies were fabricated. The monofunctional monomers acryloylmorpholin (ACMO), 2-phenoxyethyl acrylate (2-PHEA), and hydroxyethyl acrylate (HEA) with hydrophilic groups and high photopolymerization activity were used, and the resins with high activity and photopolymerization accuracy were fabricated, benefiting for fabricating Al2O3 slurries with superior rheological and photosensitive properties.
Xue Yong
,
Zheng Jie
,
Yan Zhaoming
,
Xu Jian
,
Zhang Zhimin
,
Li Xubin
,
Yang Yongbiao
,
Wang Qiang
2021, 50(5):1583-1589.
DOI: 10.12442/j.issn.1002-185X.20200310
Abstract:
Cyclic expansion-extrusion with an asymmetrical extrusion cavity (CEE-AEC) was performed on AZ31 magnesium alloy, and the effects of deformation passes on grain refinement, texture evolution, and mechanical properties were studied. The results show that during the CEE-AEC process, the continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) occur, and the average grain size reduces from 344 μm to 11.7 μm. The (0001) basal texture intensity gradually increases with the increase of processing passes. The existence of asymmetric cavities in CEE-AEC dies causes a great deflection of the basal texture. In addition, the mechanical properties of the alloy improve, and the tensile yield strength (TYS), ultimate tensile strength (UTS), and elongation (EL) are 109 MPa, 211 MPa, and 30.8%, respectively.
Cyclic expansion-extrusion with an asymmetrical extrusion cavity (CEE-AEC) was performed on AZ31 magnesium alloy, and the effects of deformation passes on grain refinement, texture evolution, and mechanical properties were studied. The results show that during the CEE-AEC process, the continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) occur, and the average grain size reduces from 344 μm to 11.7 μm. The (0001) basal texture intensity gradually increases with the increase of processing passes. The existence of asymmetric cavities in CEE-AEC dies causes a great deflection of the basal texture. In addition, the mechanical properties of the alloy improve, and the tensile yield strength (TYS), ultimate tensile strength (UTS), and elongation (EL) are 109 MPa, 211 MPa, and 30.8%, respectively.
2021, 50(5):1590-1595.
DOI: 10.12442/j.issn.1002-185X.20200304
Abstract:
Vacuum heat treatments were performed at different temperatures for the Zr-Sn-Nb alloys which were already oxidized for a certain time. Results show that the oxide film dissolution into the matrix occurs during heat treatment, and the oxygen diffusion from zirconia to nearby zirconium matrix is enhanced. Diffusion kinetics of oxygen is discussed, and the diffusion coefficient is calculated for the specific alloy. The diffusion may be attributed to the existence of oxygen content gradient and the high oxygen solubility in the matrix. ZrO is observed through microscopic chemical analysis, and the thickness of the metastable layer increases after the heat treatment. The thickness of oxygen-dissolved zirconium matrix (Zr(O)) layer also largely widens. It is speculated that in the actual aqueous corrosion procedure, there should be co-existence of oxidation and oxide film dissolution into the matrix. When the oxidation rate is restricted, the oxide film dissolution becomes obvious and facilitates the growth of metastable layer.
Vacuum heat treatments were performed at different temperatures for the Zr-Sn-Nb alloys which were already oxidized for a certain time. Results show that the oxide film dissolution into the matrix occurs during heat treatment, and the oxygen diffusion from zirconia to nearby zirconium matrix is enhanced. Diffusion kinetics of oxygen is discussed, and the diffusion coefficient is calculated for the specific alloy. The diffusion may be attributed to the existence of oxygen content gradient and the high oxygen solubility in the matrix. ZrO is observed through microscopic chemical analysis, and the thickness of the metastable layer increases after the heat treatment. The thickness of oxygen-dissolved zirconium matrix (Zr(O)) layer also largely widens. It is speculated that in the actual aqueous corrosion procedure, there should be co-existence of oxidation and oxide film dissolution into the matrix. When the oxidation rate is restricted, the oxide film dissolution becomes obvious and facilitates the growth of metastable layer.
2021, 50(5):1596-1601.
DOI: 10.12442/j.issn.1002-185X.20200337
Abstract:
The electronic structures, surface energies and thermodynamic properties of different terminated Nb2Al (100) surfaces were studied using first-principle calculations based on density functional theory. Results show that the calculated electronic structures present the enhanced metallic character and decrease covalent character for all terminated surfaces, which are attributed to the surface relaxations and the formation of surface states. According the calculated surface energies of different terminations, the surface stabilities of non-stoichiometric surfaces were analyzed. The C terminated surface (Nb22Al12) is the most thermodynamically stable surface under both Nb-rich and Al-rich conditions. Moreover, the work function of Nb2Al (100) surface was calculated, indicating that its ability to gain and lose electrons on the surface is similar to that of pure elemental surface before formation.
The electronic structures, surface energies and thermodynamic properties of different terminated Nb2Al (100) surfaces were studied using first-principle calculations based on density functional theory. Results show that the calculated electronic structures present the enhanced metallic character and decrease covalent character for all terminated surfaces, which are attributed to the surface relaxations and the formation of surface states. According the calculated surface energies of different terminations, the surface stabilities of non-stoichiometric surfaces were analyzed. The C terminated surface (Nb22Al12) is the most thermodynamically stable surface under both Nb-rich and Al-rich conditions. Moreover, the work function of Nb2Al (100) surface was calculated, indicating that its ability to gain and lose electrons on the surface is similar to that of pure elemental surface before formation.
Feng Ruicheng
,
Qi Yongnian
,
Li Haiyan
,
Song Wenyuan
,
Fan Lihe
,
Lei Chunli
,
Feng Guojin
,
Rui Zhiyuan
2021, 50(5):1602-1610.
DOI: 10.12442/j.issn.1002-185X.20200822
Abstract:
The acoustic emission (AE) response to brittle cutting of 6H-SiC was studied by molecular dynamics simulation. The micro-deformation and crack formation at atomic scale were analyzed. Furthermore, the AE sources in machining were distinguished and their corresponding AE characteristics were discussed. The results show that the brittle deformation process of 6H-SiC at cutting depth of 77 nm is simple but unusual. The deformation possesses discontinuous dislocation propagation and divides the deformed workpiece into pieces, and then the crack is initiated from a fast dislocation propagation. The compressive stress results in the decline of AE power initially. Three AE sources clustered in the frequency-energy analysis are lattice vibration, dislocation propagation and crack propagation. In addition, the AE response of two times of dislocation propagation shows a higher frequency characteristic than lattice vibration does at temperature of 1 K, with the lowest energy occupation in total. On the contrary, the AE response of crack propagation has apparent frequency and energy accumulation characteristics.
The acoustic emission (AE) response to brittle cutting of 6H-SiC was studied by molecular dynamics simulation. The micro-deformation and crack formation at atomic scale were analyzed. Furthermore, the AE sources in machining were distinguished and their corresponding AE characteristics were discussed. The results show that the brittle deformation process of 6H-SiC at cutting depth of 77 nm is simple but unusual. The deformation possesses discontinuous dislocation propagation and divides the deformed workpiece into pieces, and then the crack is initiated from a fast dislocation propagation. The compressive stress results in the decline of AE power initially. Three AE sources clustered in the frequency-energy analysis are lattice vibration, dislocation propagation and crack propagation. In addition, the AE response of two times of dislocation propagation shows a higher frequency characteristic than lattice vibration does at temperature of 1 K, with the lowest energy occupation in total. On the contrary, the AE response of crack propagation has apparent frequency and energy accumulation characteristics.
2021, 50(5):1611-1616.
DOI: 10.12442/j.issn.1002-185X.20200505
Abstract:
Considering the springback of 5182 aluminum alloy wind beam as the research object, the real stress-strain curves of 5182 aluminum alloy sheet under different rolling directions and strain rates were obtained through one-way tensile test, and introduced into the numerical simulation mode. The influence of sheet metal forming speed, die clearance, and friction coefficient on the springback of 5182 aluminum alloy windshield beams was studied and the formation mechanisms were analyzed. According to the response surface method, the prediction model of 5182 aluminum alloy windshield beam springback was established. The prediction model was verified by experiments under different conditions. The research provides a new method for the analysis of aluminum alloy sheet springback.
Considering the springback of 5182 aluminum alloy wind beam as the research object, the real stress-strain curves of 5182 aluminum alloy sheet under different rolling directions and strain rates were obtained through one-way tensile test, and introduced into the numerical simulation mode. The influence of sheet metal forming speed, die clearance, and friction coefficient on the springback of 5182 aluminum alloy windshield beams was studied and the formation mechanisms were analyzed. According to the response surface method, the prediction model of 5182 aluminum alloy windshield beam springback was established. The prediction model was verified by experiments under different conditions. The research provides a new method for the analysis of aluminum alloy sheet springback.
31 Multiscale Model for Crack Propagation of γ/γ Interface in γ-TiAl Alloy Based on Cohesive Zone Model
Li Jianhua
,
Zhang Cheng
,
Feng Ruicheng
,
Wang Junjun
,
Wang Maomao
,
Li Haiyan
,
Qi Yongnian
,
Rui Zhiyuan
2021, 50(5):1617-1625.
DOI: 10.12442/j.issn.1002-185X.20200774
Abstract:
The multiscale model was established to predict the crack propagation behavior of γ-titanium aluminide (TiAl) alloys. The constitutive parameters of the cohesive zone model (CZM) of true twin (TT) γ/γ interface were obtained by molecular dynamics (MD). The mesoscopic model of polycrystalline γ-TiAl was generated via Voronoi method, and the CZM constitutive parameters were coupled into the model. The corresponding critical stress fracture diagrams with non-defect, blunt crack and blunt crack+central cavity defect were obtained. Furthermore, the polycrystalline model and the overall force-displacement curve were averaged by the geometric similarity, and the damage mechanism of γ-TiAl alloy was analyzed. At the same time, the macroscopic finite element model (FEM) was constructed according to the homogeneous material hypothesis. A cohesive region was built in the interested crack area, and then the force-displacement relationship and fracture toughness of γ-TiAl alloy was obtained through the FEM simulation of the compact tensile specimen. Finally, the results show that the comparison between the crack propagation behavior obtained from the macroscale finite element simulation and the experimental results proves the validity of the multiscale model. The defects have a significant sensitivity on the strength of the entire near-γ structure when the ratio of grain is the same, and meanwhile this analysis method can effectively connect various scales and predict the growth of cracks.
The multiscale model was established to predict the crack propagation behavior of γ-titanium aluminide (TiAl) alloys. The constitutive parameters of the cohesive zone model (CZM) of true twin (TT) γ/γ interface were obtained by molecular dynamics (MD). The mesoscopic model of polycrystalline γ-TiAl was generated via Voronoi method, and the CZM constitutive parameters were coupled into the model. The corresponding critical stress fracture diagrams with non-defect, blunt crack and blunt crack+central cavity defect were obtained. Furthermore, the polycrystalline model and the overall force-displacement curve were averaged by the geometric similarity, and the damage mechanism of γ-TiAl alloy was analyzed. At the same time, the macroscopic finite element model (FEM) was constructed according to the homogeneous material hypothesis. A cohesive region was built in the interested crack area, and then the force-displacement relationship and fracture toughness of γ-TiAl alloy was obtained through the FEM simulation of the compact tensile specimen. Finally, the results show that the comparison between the crack propagation behavior obtained from the macroscale finite element simulation and the experimental results proves the validity of the multiscale model. The defects have a significant sensitivity on the strength of the entire near-γ structure when the ratio of grain is the same, and meanwhile this analysis method can effectively connect various scales and predict the growth of cracks.
2021, 50(5):1626-1634.
DOI: 10.12442/j.issn.1002-185X.20210015
Abstract:
The snake rolling manufacture technique provides a new method for producing high-performance heavy aluminum plates. The traditional curvature model of the asymmetrical rolling cannot be simply applied to calculate the curvature of the snake rolling. The plate curvature model of the snake rolling was set up in this research according to the roll offset and different roll radii. The deformation region consists of four different zones at most which depends on the positions of the two neutral points, and this number may drop to three or two under other conditions. The deformation zone with different composition cases was analyzed, and the models of the specific pressure and the accumulated shear strain deviation between the upper and lower parts of the plate were established. The plate curvature caused by shear strain and axial strain was calculated separately. The homogeneity coefficient E was introduced during the plate curvature modeling process to ensure the model accuracy. Then the total plate curvature model was established. Ansys software simulation can well restore the snake rolling process, and the indirect experiments were also conducted to verify the precision of plate curvature theoretical model. The results show that the maximum and minimum relative error is 10.71% and 0.34%, respectively, compared to results of simulation method and the indirect experiments, indicating that the model can be applied for the online plate curvature control application with the effect of some self-learning methods. The plate curvature affecting law with different process parameters (roll offset, roll radius ratio, rolling reduction, and initial work piece thickness) was obtained. This research about the plate curvature modeling provides important references for the production of heavy aluminum plate snake rolling.
The snake rolling manufacture technique provides a new method for producing high-performance heavy aluminum plates. The traditional curvature model of the asymmetrical rolling cannot be simply applied to calculate the curvature of the snake rolling. The plate curvature model of the snake rolling was set up in this research according to the roll offset and different roll radii. The deformation region consists of four different zones at most which depends on the positions of the two neutral points, and this number may drop to three or two under other conditions. The deformation zone with different composition cases was analyzed, and the models of the specific pressure and the accumulated shear strain deviation between the upper and lower parts of the plate were established. The plate curvature caused by shear strain and axial strain was calculated separately. The homogeneity coefficient E was introduced during the plate curvature modeling process to ensure the model accuracy. Then the total plate curvature model was established. Ansys software simulation can well restore the snake rolling process, and the indirect experiments were also conducted to verify the precision of plate curvature theoretical model. The results show that the maximum and minimum relative error is 10.71% and 0.34%, respectively, compared to results of simulation method and the indirect experiments, indicating that the model can be applied for the online plate curvature control application with the effect of some self-learning methods. The plate curvature affecting law with different process parameters (roll offset, roll radius ratio, rolling reduction, and initial work piece thickness) was obtained. This research about the plate curvature modeling provides important references for the production of heavy aluminum plate snake rolling.
Li Yahao
,
Tang Yu
,
Ye Yicong
,
Li Shun
,
Wan Hong
,
Liu Xiyue
,
Zhu Li’an
,
Wang Zhen
,
Bai Shuxin
2021, 50(5):1635-1640.
DOI: 10.12442/j.issn.1002-185X.20200474
Abstract:
In this paper, by collecting and summarizing the reported overall composition and phase composition of 18 eutectic high-entropy alloys (EHEAs), some parameters reflecting their properties were calculated, including mixing enthalpy, mixing entropy, Gibbs free energy, atomic size mismatch, the electronegativity difference and the valence electron concentration , and the influence of these parameters on the structure of the alloy were analyzed from a thermodynamic point of view. It is found that the calculated mixed entropy equivalent of the overall composition of the eutectic high-entropy alloy basically meets the structural criterion requirements of the traditional high-entropy alloy to form a single-phase solid solution. (Such as △Smix >11 J/(mol·K)、-15 kJ/mol < △Hmix < 5 kJ/mol、δ < 6.6%) But because the average free energy of the eutectic phase is lower than the total free energy when the whole forms a single phase, this makes the eutectic high-entropy alloy in the solidification process A eutectic reaction occurs, forming a multi-phase structure.
In this paper, by collecting and summarizing the reported overall composition and phase composition of 18 eutectic high-entropy alloys (EHEAs), some parameters reflecting their properties were calculated, including mixing enthalpy, mixing entropy, Gibbs free energy, atomic size mismatch, the electronegativity difference and the valence electron concentration , and the influence of these parameters on the structure of the alloy were analyzed from a thermodynamic point of view. It is found that the calculated mixed entropy equivalent of the overall composition of the eutectic high-entropy alloy basically meets the structural criterion requirements of the traditional high-entropy alloy to form a single-phase solid solution. (Such as △Smix >11 J/(mol·K)、-15 kJ/mol < △Hmix < 5 kJ/mol、δ < 6.6%) But because the average free energy of the eutectic phase is lower than the total free energy when the whole forms a single phase, this makes the eutectic high-entropy alloy in the solidification process A eutectic reaction occurs, forming a multi-phase structure.
2021, 50(5):1641-1648.
DOI: 10.12442/j.issn.1002-185X.20200452
Abstract:
Porous NiCrMoCu alloys were fabricated by reactive synthesis sintering technique with Ni, Cr, Mo and Cu element powders as raw materials. Phase composition, the volume expansion ratio, pore structures and pore morphology were characterized and the pore forming mechanism was discussed. The results indicate that the pore size, porosity and volume expansion rate of porous materials increase with the increase of Cr amount. When the Cr content is 30 wt%, the open porosity reaches 42.10%, the total porosity is 48.36%, the volume expansion rate is 12.60%, the average pore size and permeability are 13.32 μm and 96.3 m3?m-2?kpa-1?h-1, respectively. The diffusion rates of Cr, Mo, Cu atoms in different matrix elements at 1150 ℃ are calculated, and the calculation results illustrate that the diffusion rates of Cr atoms in Ni and Cu atoms are 1.61×10-14 m2?s-1 and 8.22××10-13 m2?s-1, respectively, which is higher than the diffusion rates of Mo and Cu atoms. The pore forming mechanism is explored and it is mainly based on the inter-connected pores in the green compacts and the Kirkendall effect due to the different diffusion rates of Cr, Mo and Cu atoms in the nickel substrate.
Porous NiCrMoCu alloys were fabricated by reactive synthesis sintering technique with Ni, Cr, Mo and Cu element powders as raw materials. Phase composition, the volume expansion ratio, pore structures and pore morphology were characterized and the pore forming mechanism was discussed. The results indicate that the pore size, porosity and volume expansion rate of porous materials increase with the increase of Cr amount. When the Cr content is 30 wt%, the open porosity reaches 42.10%, the total porosity is 48.36%, the volume expansion rate is 12.60%, the average pore size and permeability are 13.32 μm and 96.3 m3?m-2?kpa-1?h-1, respectively. The diffusion rates of Cr, Mo, Cu atoms in different matrix elements at 1150 ℃ are calculated, and the calculation results illustrate that the diffusion rates of Cr atoms in Ni and Cu atoms are 1.61×10-14 m2?s-1 and 8.22××10-13 m2?s-1, respectively, which is higher than the diffusion rates of Mo and Cu atoms. The pore forming mechanism is explored and it is mainly based on the inter-connected pores in the green compacts and the Kirkendall effect due to the different diffusion rates of Cr, Mo and Cu atoms in the nickel substrate.
2021, 50(5):1649-1655.
DOI: 10.12442/j.issn.1002-185X.20200899
Abstract:
The influence of wire compositions with different Cu, Fe and Si content on the microstructures and mechanical properties of heat treated WAAM single-walls was studied. It was found that the yielding strength of WAAM samples was low when the Cu content (5.3wt%) in wire was insufficient. When the Cu content in wire slightly exceeded the maximum solid solubility of Cu (5.65wt%) in α(Al), the yielding strength of WAAM samples increased without deteriorating the plasticity although there were some residual θ(Al2Cu) phases. When the wire had approiate Cu content (5.8-6.5wt%) with low Si content(<0.08wt%), the yielding strength of WAAM samples decreased with the increasing of Fe content due to the redueced amount of strengthening phases and increased amount of θ phases and α(Fe) compounds. When the wire had approiate Cu content with high Fe and Si content(>0.15wt%), the plasiticity in vertical direction of WAAM samples deteriorated due to the existing of acicular β(Fe) compounds in the interlayer region of the samples. Using the wire with low inpurities content (Si<0.08wt%,Fe<0.15wt%) and approiate Cu content (5.8-6.5wt%), the WAAM samples possesed the excellent mechancial properits with average tensile strength, yielding strength and elongation after fracture exceeding 440MPa, 300MPa and 10%, respectively.
The influence of wire compositions with different Cu, Fe and Si content on the microstructures and mechanical properties of heat treated WAAM single-walls was studied. It was found that the yielding strength of WAAM samples was low when the Cu content (5.3wt%) in wire was insufficient. When the Cu content in wire slightly exceeded the maximum solid solubility of Cu (5.65wt%) in α(Al), the yielding strength of WAAM samples increased without deteriorating the plasticity although there were some residual θ(Al2Cu) phases. When the wire had approiate Cu content (5.8-6.5wt%) with low Si content(<0.08wt%), the yielding strength of WAAM samples decreased with the increasing of Fe content due to the redueced amount of strengthening phases and increased amount of θ phases and α(Fe) compounds. When the wire had approiate Cu content with high Fe and Si content(>0.15wt%), the plasiticity in vertical direction of WAAM samples deteriorated due to the existing of acicular β(Fe) compounds in the interlayer region of the samples. Using the wire with low inpurities content (Si<0.08wt%,Fe<0.15wt%) and approiate Cu content (5.8-6.5wt%), the WAAM samples possesed the excellent mechancial properits with average tensile strength, yielding strength and elongation after fracture exceeding 440MPa, 300MPa and 10%, respectively.
2021, 50(5):1760-1766.
DOI: 10.12442/j.issn.1002-185X.20200435
Abstract:
In order to investigate the influence of the forming method and forming direction of TA15 titanium alloy on the microstructure and ultrasonic parameters,so as to clarify the acoustic properties of the material,the TA15 titanium alloy is manufactured by forging and laser deposition.The test specimens with the same cross hole defect and same standard size are manufactured.Ultrasonic non-destructive testing equipment is used to inspect the sample to obtain the defect amplitude,longitudinal wave sound velocity,and ultrasonic attenuation coefficient of the sample, and the optical microscope(OM)is used for the observation of the microstructure.The results indicate that the forming method affect the tissue characteristics, and then affect the ultrasonic parameters.The laser deposition manufacturing sample has obvious tissue anisotropy,which results in a large difference in ultrasonic parameters in different forming directions.Compared with laser-deposited sample,the length-width ratio of lath shape ɑ phase in the microstructure of the double-annealing sample have a decrease,resulting in an average reduction of the longitudinal sound velocity in all directions by 167 m/s and an increase by 13%~20% in attenuation coefficient.And compared with the forged sample,under the joint action of the difference between macro organization and micro organization, the X-direction and Z-direction longitudinal wave sound velocity decreases by 392 m/s and 466 m/s respectively, and the attenuation coefficient increases by 39% and 55% respectively.The research results have certain reference value for the ultrasonic non-destructive testing of laser additive parts and the non-destructive evaluation of internal defects of TA15 titanium alloy materials.
In order to investigate the influence of the forming method and forming direction of TA15 titanium alloy on the microstructure and ultrasonic parameters,so as to clarify the acoustic properties of the material,the TA15 titanium alloy is manufactured by forging and laser deposition.The test specimens with the same cross hole defect and same standard size are manufactured.Ultrasonic non-destructive testing equipment is used to inspect the sample to obtain the defect amplitude,longitudinal wave sound velocity,and ultrasonic attenuation coefficient of the sample, and the optical microscope(OM)is used for the observation of the microstructure.The results indicate that the forming method affect the tissue characteristics, and then affect the ultrasonic parameters.The laser deposition manufacturing sample has obvious tissue anisotropy,which results in a large difference in ultrasonic parameters in different forming directions.Compared with laser-deposited sample,the length-width ratio of lath shape ɑ phase in the microstructure of the double-annealing sample have a decrease,resulting in an average reduction of the longitudinal sound velocity in all directions by 167 m/s and an increase by 13%~20% in attenuation coefficient.And compared with the forged sample,under the joint action of the difference between macro organization and micro organization, the X-direction and Z-direction longitudinal wave sound velocity decreases by 392 m/s and 466 m/s respectively, and the attenuation coefficient increases by 39% and 55% respectively.The research results have certain reference value for the ultrasonic non-destructive testing of laser additive parts and the non-destructive evaluation of internal defects of TA15 titanium alloy materials.
2021, 50(5):1767-1774.
DOI: 10.12442/j.issn.1002-185X.20200442
Abstract:
An experimental device for centrifugal atomization of rotating disk was developed independently, then, high fluidity aluminium alloy powder for additive manufacturing were produced by the self-developed experimental device, and the better shape of the atomized disk was obtained by experimental study. The properties of aluminum alloy powder produced by centrifugal atomization and the physical properties of 3D printed parts were tested. Results show that the powder made by centrifugal atomization is high fluidity, narrow size distribution, good spherical, high apparent density, no hollow powder and the surface is smooth without satellite powder, etc. Moreover, the 3D printing sample of centrifugal atomization powder has more uniform laser cladding coating and less hole defects, and its density and mechanical properties are significantly better than those of gas atomization powder, especially, tensile strength and yield strength of 3D printing sample reaches 495MPa and 320 MPa, which is nearly 10% higher than that of gas atomization powder.
An experimental device for centrifugal atomization of rotating disk was developed independently, then, high fluidity aluminium alloy powder for additive manufacturing were produced by the self-developed experimental device, and the better shape of the atomized disk was obtained by experimental study. The properties of aluminum alloy powder produced by centrifugal atomization and the physical properties of 3D printed parts were tested. Results show that the powder made by centrifugal atomization is high fluidity, narrow size distribution, good spherical, high apparent density, no hollow powder and the surface is smooth without satellite powder, etc. Moreover, the 3D printing sample of centrifugal atomization powder has more uniform laser cladding coating and less hole defects, and its density and mechanical properties are significantly better than those of gas atomization powder, especially, tensile strength and yield strength of 3D printing sample reaches 495MPa and 320 MPa, which is nearly 10% higher than that of gas atomization powder.
2021, 50(5):1775-1780.
DOI: 10.12442/j.issn.1002-185X.20200451
Abstract:
In this paper, a new high-strength corrosion-resistant titanium alloy is taken as the research object, and its titanium alloy hot-rolled sheet is subjected to different solution aging heat treatments. The effects of solution aging processes on the microstructure, texture, mechanical properties and corrosion resistance of titanium alloy sheets were studied. The results show that when the solution temperature is increased from 900 ℃ to 930 ℃, the equiaxed α-phase and β-transformed structures are significantly increased, and they are all equiaxed morphologies. When the solution temperature is increased to 960 ℃, the equiaxed α-phase and β-transformed structures decrease, and a large number of needle-like secondary α-phases appear, and the structure changes from the equiaxed structure to the dual-state structure. With the increase of solution temperature, the strength and hardness of the plate increase, and the plasticity gradually decreases, while the corrosion current density and corrosion rate show a trend of decreasing first and then increasing. After the Ti603 titanium alloy plate is treated at 900 ℃ for 30 minutes and aging at 580 ℃ for 3 hours, it has the best comprehensive mechanical properties and good corrosion resistance.
In this paper, a new high-strength corrosion-resistant titanium alloy is taken as the research object, and its titanium alloy hot-rolled sheet is subjected to different solution aging heat treatments. The effects of solution aging processes on the microstructure, texture, mechanical properties and corrosion resistance of titanium alloy sheets were studied. The results show that when the solution temperature is increased from 900 ℃ to 930 ℃, the equiaxed α-phase and β-transformed structures are significantly increased, and they are all equiaxed morphologies. When the solution temperature is increased to 960 ℃, the equiaxed α-phase and β-transformed structures decrease, and a large number of needle-like secondary α-phases appear, and the structure changes from the equiaxed structure to the dual-state structure. With the increase of solution temperature, the strength and hardness of the plate increase, and the plasticity gradually decreases, while the corrosion current density and corrosion rate show a trend of decreasing first and then increasing. After the Ti603 titanium alloy plate is treated at 900 ℃ for 30 minutes and aging at 580 ℃ for 3 hours, it has the best comprehensive mechanical properties and good corrosion resistance.
2021, 50(5):1781-1786.
DOI: 10.12442/j.issn.1002-185X.20200455
Abstract:
Changing the structure of lithium titanate (Li4Ti5O12, Abbre. LTO) material by delithiation (activation) in advance, to increase the internal lithium ion vacancy and enhance the lithium intercalation ability, a high specific capacity LTO was prepared; and CMF (carbon nanotubes macro film) was introduced as a current collector instead of metal foil to improve its electrochemical stability; finally, a Li4Ti5O12 electrode having high specific capacity and high stability was obtained. Characterization was executed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical testing. The results show that the activated Li4Ti5O12 can achieve a specific capacity of 192.7 mAh/g at 1C rate, which is about 30 mAh/g higher than that of the normal Li4Ti5O12 material. The introduced CMF current collector can enhance the binding force with the active material, and it still possesses a specific capacity of 150 mAh/g at 5C rate , exhibiting excellent rate performance.
Changing the structure of lithium titanate (Li4Ti5O12, Abbre. LTO) material by delithiation (activation) in advance, to increase the internal lithium ion vacancy and enhance the lithium intercalation ability, a high specific capacity LTO was prepared; and CMF (carbon nanotubes macro film) was introduced as a current collector instead of metal foil to improve its electrochemical stability; finally, a Li4Ti5O12 electrode having high specific capacity and high stability was obtained. Characterization was executed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical testing. The results show that the activated Li4Ti5O12 can achieve a specific capacity of 192.7 mAh/g at 1C rate, which is about 30 mAh/g higher than that of the normal Li4Ti5O12 material. The introduced CMF current collector can enhance the binding force with the active material, and it still possesses a specific capacity of 150 mAh/g at 5C rate , exhibiting excellent rate performance.
2021, 50(5):1787-1794.
DOI: 10.12442/j.issn.1002-185X.20200463
Abstract:
The high-temperature titanium alloy mesh rib panel is more efficient than the traditional aluminum alloy rib wall plate, but the titanium alloy monolithic wall plate is difficult to form at room temperature. The use of current electroplasticity effect and Joule heat effect can effectively reduce the forming load and increase the forming limit, and can effectively avoid the problem of serious oxidation oxidation of titanium alloy.In this paper, the electric-thermo-mechanical coupled finite element model of electric pulse assisted bending forming of Ti55 integral panel is established, and different forming process parameters and panel geometric parameters are simulated. The results show that 8A/mm2 current is applied at both ends of the wall plate For density, the temperature range of press forming is more suitable. As the height of the ribs increases, the degree of instability buckling becomes larger and larger. The smaller the critical load required when the ribs are unstable, the worse the stability of the ribs. The thickness of the web mainly affects the temperature of the ribs and thus the instability of the ribs. The greater the spacing of the transverse ribs of the overall wall panel, the worse the stability of the ribs and the more serious the buckling of the buckling.
The high-temperature titanium alloy mesh rib panel is more efficient than the traditional aluminum alloy rib wall plate, but the titanium alloy monolithic wall plate is difficult to form at room temperature. The use of current electroplasticity effect and Joule heat effect can effectively reduce the forming load and increase the forming limit, and can effectively avoid the problem of serious oxidation oxidation of titanium alloy.In this paper, the electric-thermo-mechanical coupled finite element model of electric pulse assisted bending forming of Ti55 integral panel is established, and different forming process parameters and panel geometric parameters are simulated. The results show that 8A/mm2 current is applied at both ends of the wall plate For density, the temperature range of press forming is more suitable. As the height of the ribs increases, the degree of instability buckling becomes larger and larger. The smaller the critical load required when the ribs are unstable, the worse the stability of the ribs. The thickness of the web mainly affects the temperature of the ribs and thus the instability of the ribs. The greater the spacing of the transverse ribs of the overall wall panel, the worse the stability of the ribs and the more serious the buckling of the buckling.
2021, 50(5):1795-1802.
DOI: 10.12442/j.issn.1002-185X.20200464
Abstract:
30vol%TiB2/Al composites were fabricated by squeeze casting technology, and its self-lubricating characteristics under low load and high speed were found. Therefore, the influence of load, sliding speed and friction pair on the friction behavior of the material was studied by means of friction tests in the paper. The results show that in dry sliding wear mode, at 0.8m/s sliding velocity, with the increase of the load, the average friction coefficient of TiB2/Al composite with GCr15 was basically unchanged, but the fluctuation amplitude of the instantaneous friction coefficient decreased, and the standard deviation of the friction coefficient decreased. While at 0.49N，the average friction coefficient did not change significantly with the increase of sliding velocity, fluctuating between 0.165-0.255.The friction coefficient dispersion of TiB2/Al composites under constant loading and variable velocity is higher than that under constant loading and variable velocity. When GCr15 is used as friction pair, the turbulent fluctuation of instantaneous friction coefficient is larger than that of composite itself. The average friction coefficient of composites was stable at about 0.08.When grinding with GCr15, the average friction coefficient was stable at about 0.18.
30vol%TiB2/Al composites were fabricated by squeeze casting technology, and its self-lubricating characteristics under low load and high speed were found. Therefore, the influence of load, sliding speed and friction pair on the friction behavior of the material was studied by means of friction tests in the paper. The results show that in dry sliding wear mode, at 0.8m/s sliding velocity, with the increase of the load, the average friction coefficient of TiB2/Al composite with GCr15 was basically unchanged, but the fluctuation amplitude of the instantaneous friction coefficient decreased, and the standard deviation of the friction coefficient decreased. While at 0.49N，the average friction coefficient did not change significantly with the increase of sliding velocity, fluctuating between 0.165-0.255.The friction coefficient dispersion of TiB2/Al composites under constant loading and variable velocity is higher than that under constant loading and variable velocity. When GCr15 is used as friction pair, the turbulent fluctuation of instantaneous friction coefficient is larger than that of composite itself. The average friction coefficient of composites was stable at about 0.08.When grinding with GCr15, the average friction coefficient was stable at about 0.18.
2021, 50(5):1803-1811.
DOI: 10.12442/j.issn.1002-185X.20200467
Abstract:
The effect of microstructure on fatigue behavior of 7020 aluminum alloy profile was investigated by optical microscopy, scanning electron microscopy, scanning transmission electron microscopy and electron back scattering diffraction technique. The results show that the fatigue strength of the alloy is 232.9MPa at 107 cycles of loading, under the stress ratio R of 0. The fatigue crack growth rate is about 6.44×10-5mm/cycle at ΔK of 8MPa·m1/2. The coarse high-melting intermetallic compounds with a size of 3 to 12μm in the alloy not only easily become the initiation of fatigue crack, but also accelerate fatigue crack growth. In the unrecrystallized area, the fatigue crack growth of the alloy mainly occurred by a transgranular mechanism. When the adjacent grains are small equiaxed recrystallized grains with high misorientation, fatigue cracks would propagate rapidly along the grain boundaries. The lower the proportion of recrystallization and its corresponding high-angle grain boundaries, the more tortuous of the fatigue crack propagation path. Under these conditions, the fatigue crack of the alloy propagates slowly.
The effect of microstructure on fatigue behavior of 7020 aluminum alloy profile was investigated by optical microscopy, scanning electron microscopy, scanning transmission electron microscopy and electron back scattering diffraction technique. The results show that the fatigue strength of the alloy is 232.9MPa at 107 cycles of loading, under the stress ratio R of 0. The fatigue crack growth rate is about 6.44×10-5mm/cycle at ΔK of 8MPa·m1/2. The coarse high-melting intermetallic compounds with a size of 3 to 12μm in the alloy not only easily become the initiation of fatigue crack, but also accelerate fatigue crack growth. In the unrecrystallized area, the fatigue crack growth of the alloy mainly occurred by a transgranular mechanism. When the adjacent grains are small equiaxed recrystallized grains with high misorientation, fatigue cracks would propagate rapidly along the grain boundaries. The lower the proportion of recrystallization and its corresponding high-angle grain boundaries, the more tortuous of the fatigue crack propagation path. Under these conditions, the fatigue crack of the alloy propagates slowly.
2021, 50(5):1812-1816.
DOI: 10.12442/j.issn.1002-185X.20200471
Abstract:
As a kind of high quality metal material, magnesium is widely used in various fields. There is little research on the molecular level of magnesium. In this paper, the effect of temperature on the properties of single crystal magnesium at a tensile rate of 10^10s^-1 was studied by using molecular dynamics simulation method, and stress-strain analysis, potential energy strain analysis, common neighbor analysis, dislocation density analysis and other operations were performed on the results. The results show that the peak tensile strength of monocrystalline magnesium decreases with the increase of temperature, and the corresponding strain value of each peak point decreases with the increase of temperature. HCP before the peak stress appears first converted into Other structures without dislocation, after the peak stress in the FCC, BCC structure appeared at the same time produce dislocation, dislocation mainly for 1/3<-1100> dislocation and unknown dislocation structure, the corresponding crystal structure transformation and the generation of dislocation about lag strain values of stress peaks around 0.45%, and the effects of temperature on lag value is not big, crystal structure transformation and the generation of dislocation and with the increase of temperature in advance.
As a kind of high quality metal material, magnesium is widely used in various fields. There is little research on the molecular level of magnesium. In this paper, the effect of temperature on the properties of single crystal magnesium at a tensile rate of 10^10s^-1 was studied by using molecular dynamics simulation method, and stress-strain analysis, potential energy strain analysis, common neighbor analysis, dislocation density analysis and other operations were performed on the results. The results show that the peak tensile strength of monocrystalline magnesium decreases with the increase of temperature, and the corresponding strain value of each peak point decreases with the increase of temperature. HCP before the peak stress appears first converted into Other structures without dislocation, after the peak stress in the FCC, BCC structure appeared at the same time produce dislocation, dislocation mainly for 1/3<-1100> dislocation and unknown dislocation structure, the corresponding crystal structure transformation and the generation of dislocation about lag strain values of stress peaks around 0.45%, and the effects of temperature on lag value is not big, crystal structure transformation and the generation of dislocation and with the increase of temperature in advance.
2021, 50(5):1817-1825.
DOI: 10.12442/j.issn.1002-185X.20200480
Abstract:
With sodium bicarbonate and sodium silicate as silica materials, molybdenum ions were loaded onto silica gel surface by sol-gel method to prepare antibacterial molybdenum silica gel. The best preparation conditions were obtained by single factor experiment. XRD, ICP, SEM, EDS, XPS and BET were used to characterize the crystal structure, ion concentration, apparent morphology, loading form and specific surface area of the material. In addition, the antibacterial properties of the samples were tested by plate coating method. The photocatalytic effect of the composite was investigated by observing the degradation of methylene blue solution under different light sources. Finally, the antibacterial and photocatalytic mechanism of the material were discussed. The results showed that the amorphous molybdenum photocatalytic antibacterial material was successfully prepared without changing the structure and morphology of silica gel, and the bactericidal effect on Escherichia coli was good. The methylene blue solution has ideal degradation effect under ultraviolet and visible light. The material has the unique characteristics of photocatalytic antibacterial material, not only antibacterial effect and photodegradation function, but also good circulation.
With sodium bicarbonate and sodium silicate as silica materials, molybdenum ions were loaded onto silica gel surface by sol-gel method to prepare antibacterial molybdenum silica gel. The best preparation conditions were obtained by single factor experiment. XRD, ICP, SEM, EDS, XPS and BET were used to characterize the crystal structure, ion concentration, apparent morphology, loading form and specific surface area of the material. In addition, the antibacterial properties of the samples were tested by plate coating method. The photocatalytic effect of the composite was investigated by observing the degradation of methylene blue solution under different light sources. Finally, the antibacterial and photocatalytic mechanism of the material were discussed. The results showed that the amorphous molybdenum photocatalytic antibacterial material was successfully prepared without changing the structure and morphology of silica gel, and the bactericidal effect on Escherichia coli was good. The methylene blue solution has ideal degradation effect under ultraviolet and visible light. The material has the unique characteristics of photocatalytic antibacterial material, not only antibacterial effect and photodegradation function, but also good circulation.
2021, 50(5):1826-1832.
DOI: 10.12442/j.issn.1002-185X.20200481
Abstract:
In this paper, the microstructure and mechanical properties of Mg-4Y-3Nd-1.5Al alloy with different heat treatment conditions were carried out by microstructural analysis and mechanical property testing. The experimental results show that there are Mg5RE, Mg24RE5 and Al2RE intermetallic phases in as-cast Mg-4Y-3Nd-1.5Al alloy and the Mg5RE and Mg24RE5 phases dissolved into α-Mg matrix and Al2RE phases is stable in solid-solution treated Mg-4Y-3Nd-1.5Al alloy. The Mg-4Y-3Nd-1.5Al alloy has an obvious aging hardening effect and the mechanical property can be improved obviously by solution + aging treatment. The yield strength, ultimate tensile strength and elongation of Mg-4Y-3Nd-1.5Al alloy after solution (525℃×6h+550℃×12h)+peak aging (225℃×10h) are 85MPa, 262MPa and 6.5%, respectively. The high density and fine precipitation β" and β" are responsible for the excellent mechanical properties of heat treated Mg-4Y-3Nd-1.5Al alloy.
In this paper, the microstructure and mechanical properties of Mg-4Y-3Nd-1.5Al alloy with different heat treatment conditions were carried out by microstructural analysis and mechanical property testing. The experimental results show that there are Mg5RE, Mg24RE5 and Al2RE intermetallic phases in as-cast Mg-4Y-3Nd-1.5Al alloy and the Mg5RE and Mg24RE5 phases dissolved into α-Mg matrix and Al2RE phases is stable in solid-solution treated Mg-4Y-3Nd-1.5Al alloy. The Mg-4Y-3Nd-1.5Al alloy has an obvious aging hardening effect and the mechanical property can be improved obviously by solution + aging treatment. The yield strength, ultimate tensile strength and elongation of Mg-4Y-3Nd-1.5Al alloy after solution (525℃×6h+550℃×12h)+peak aging (225℃×10h) are 85MPa, 262MPa and 6.5%, respectively. The high density and fine precipitation β" and β" are responsible for the excellent mechanical properties of heat treated Mg-4Y-3Nd-1.5Al alloy.
2021, 50(5):1833-1839.
DOI: 10.12442/j.issn.1002-185X.20200488
Abstract:
The high cycle fatigue performance and fracture mechanism of 2A70 aluminum alloy after laser and vibration marking were studied.The results showed that compared with the base material, the high cycle fatigue life of 2A70 alloy after vibration marking decreased by 57% and that of laser marking decreased by 94%, which was only 14% of the fatigue life of vibration marking.Compared with laser marking, the topography near vibration marking is more gentle, the stress concentration degree is smaller, the S "phase size is smaller and the volume fraction is higher.Al9FeNi phase has smaller size, higher volume fraction, lower crack initiation and propagation rate, and longer fatigue life.The high cycle fatigue performance of 2A70 aluminum alloy under vibration marking is much better than that under laser marking due to the joint action of stress concentration, precipitation phase size and volume fraction.S
The high cycle fatigue performance and fracture mechanism of 2A70 aluminum alloy after laser and vibration marking were studied.The results showed that compared with the base material, the high cycle fatigue life of 2A70 alloy after vibration marking decreased by 57% and that of laser marking decreased by 94%, which was only 14% of the fatigue life of vibration marking.Compared with laser marking, the topography near vibration marking is more gentle, the stress concentration degree is smaller, the S "phase size is smaller and the volume fraction is higher.Al9FeNi phase has smaller size, higher volume fraction, lower crack initiation and propagation rate, and longer fatigue life.The high cycle fatigue performance of 2A70 aluminum alloy under vibration marking is much better than that under laser marking due to the joint action of stress concentration, precipitation phase size and volume fraction.S
2021, 50(5):1840-1852.
DOI: 10.12442/j.issn.1002-185X.20200814
Abstract:
The development of films with good cycle stability, fast coloring / fading response and high coloring efficiency is research focus of electrochromic materials. Compared with the organic materials, inorganic materials have stronger stability and better practicability. The electrochromic properties can be effectively improved by constructing micro-nano structural active films with high porosity, low resistivity, large specific surface area and multiple active sites. In this paper, the principle of electrochromic devices is described. The performance advantages and development status of inorganic electrochromic thin films with special micro-nano structures such as mesoporous structure, nano-array structure and core-shell structure are introduced in detail. Furthermore, the bottleneck problems and future research and development trends of micro-nanostructure thin films are discussed. It is helpful to expand the research ideas accurately and play a guiding role in promoting the development and application of inorganic electrochromic materials.
The development of films with good cycle stability, fast coloring / fading response and high coloring efficiency is research focus of electrochromic materials. Compared with the organic materials, inorganic materials have stronger stability and better practicability. The electrochromic properties can be effectively improved by constructing micro-nano structural active films with high porosity, low resistivity, large specific surface area and multiple active sites. In this paper, the principle of electrochromic devices is described. The performance advantages and development status of inorganic electrochromic thin films with special micro-nano structures such as mesoporous structure, nano-array structure and core-shell structure are introduced in detail. Furthermore, the bottleneck problems and future research and development trends of micro-nanostructure thin films are discussed. It is helpful to expand the research ideas accurately and play a guiding role in promoting the development and application of inorganic electrochromic materials.
2021, 50(5):1853-1859.
DOI: 10.12442/j.issn.1002-185X.20200457
Abstract:
Resin based Carbon fiber reinforced plastics (CFRP), as the cutting-edge light-weight composite material, are widely used in the aerospace parts. The main technologies to bond CFRPs and metals are namely adhesive bonding and mechanical bonding, which includes limitation in some area . However, laser welding technology possesses the advantages of low heat input and small deformation after welding, therefore, it can be applied to the bonding of composites and metals. This paper reviewed the bonding mechanisms and the joint defects of the joints between the CFRP materials and the common used metal like aluminum alloys, titanium alloys and carbon steels by laser welding process, and analyzed the effect of welding process, structural optimal and pre-surface treatment on the property of joint, Finally, the prospect of the CFRP/metal joint formed by laser welding are presented in this paper.
Resin based Carbon fiber reinforced plastics (CFRP), as the cutting-edge light-weight composite material, are widely used in the aerospace parts. The main technologies to bond CFRPs and metals are namely adhesive bonding and mechanical bonding, which includes limitation in some area . However, laser welding technology possesses the advantages of low heat input and small deformation after welding, therefore, it can be applied to the bonding of composites and metals. This paper reviewed the bonding mechanisms and the joint defects of the joints between the CFRP materials and the common used metal like aluminum alloys, titanium alloys and carbon steels by laser welding process, and analyzed the effect of welding process, structural optimal and pre-surface treatment on the property of joint, Finally, the prospect of the CFRP/metal joint formed by laser welding are presented in this paper.
2021, 50(5):1860-1866.
DOI: 10.12442/j.issn.1002-185X.20200459
Abstract:
Superalloy exhibits excellent overall performance at high temperature. As a result, it is widely used in the field of aerospace, petrochemical engineering and so on. Superalloy ring forging is mainly used in the component of receiver, combustor, sealing ring, et al. With the development of high performance aero-engine, the demand of superalloy ring forging with high quality keeps increasing. Previously, most focus is put on superalloy used for turbine disks and blades. Related research is carried out on alloy design and optimization, manufacture technology and deformation mechanism. However, there is only limited work about superalloy ring forging. Hence, in this work, the development of ring rolling technology of superalloy ring forging is summarized. The application of numerical simulation technique in manufacture process design of superalloy ring forging is discussed. The main superalloy used as ring forging is compared. At last, the difficulty in microstructure control during ring rolling process of superalloy analyzed. This review work is made hoping to provide some theoretical guidance for the research and development of superalloy ring forging with high quality.
Superalloy exhibits excellent overall performance at high temperature. As a result, it is widely used in the field of aerospace, petrochemical engineering and so on. Superalloy ring forging is mainly used in the component of receiver, combustor, sealing ring, et al. With the development of high performance aero-engine, the demand of superalloy ring forging with high quality keeps increasing. Previously, most focus is put on superalloy used for turbine disks and blades. Related research is carried out on alloy design and optimization, manufacture technology and deformation mechanism. However, there is only limited work about superalloy ring forging. Hence, in this work, the development of ring rolling technology of superalloy ring forging is summarized. The application of numerical simulation technique in manufacture process design of superalloy ring forging is discussed. The main superalloy used as ring forging is compared. At last, the difficulty in microstructure control during ring rolling process of superalloy analyzed. This review work is made hoping to provide some theoretical guidance for the research and development of superalloy ring forging with high quality.
2021, 50(5):1867-1882.
DOI: 10.12442/j.issn.1002-185X.20200462
Abstract:
Characteristics of room temperature brittleness for the rare material Ti-Al intermetallic compounds limit the choice of precision machining technology and its application in aerospace and national defense to a certain extent. In order to promote the adaptability of rare alloy materials in precision machining technology and high quality and high efficiency to obtain good surface quality. This article reviews the research technology on the precision machining of Ti-Al intermetallic compounds. First, the material properties of such materials and the overall status of precision machining technology are summarized. Subsequently, the cutting performance (material removal mechanism, cutting force, cutting temperature, chip shape and tool wear) of the machinability is mainly analyzed. Simultaneously summarize the surface integrity (surface roughness, surface defects, residual stress, work hardening and microstructure) of the material after processing. Finally, the ultrasonic vibration-assisted machining technology used in Ti-Al intermetallic compounds is prospected to provide a certain theoretical basis and technical support for the processing of such materials.
Characteristics of room temperature brittleness for the rare material Ti-Al intermetallic compounds limit the choice of precision machining technology and its application in aerospace and national defense to a certain extent. In order to promote the adaptability of rare alloy materials in precision machining technology and high quality and high efficiency to obtain good surface quality. This article reviews the research technology on the precision machining of Ti-Al intermetallic compounds. First, the material properties of such materials and the overall status of precision machining technology are summarized. Subsequently, the cutting performance (material removal mechanism, cutting force, cutting temperature, chip shape and tool wear) of the machinability is mainly analyzed. Simultaneously summarize the surface integrity (surface roughness, surface defects, residual stress, work hardening and microstructure) of the material after processing. Finally, the ultrasonic vibration-assisted machining technology used in Ti-Al intermetallic compounds is prospected to provide a certain theoretical basis and technical support for the processing of such materials.
