Volume 51,Issue 3,2022 Table of Contents
2022, 51(3):765-771.
DOI: 10.12442/j.issn.1002-185X.20210018
Abstract:
The Ag-TiB2 contact materials with Ag powders of different sizes were prepared by spark plasma sintering. The relative density, electroconductivity, and hardness of Ag-4wt% TiB2 contact materials were measured, and the arc erosion behavior of the contact materials was analyzed under the vacuum condition. The surface morphologies of Ag-4wt% TiB2 contact materials after arc erosion were characterized by the scanning electron microscope. The arc duration was determined by the discharged waveform recorded by a Tektronix TDS-2014 dual channel digital memory oscilloscope, and the arc erosion mechanism was discussed. The results show that the relative density, electroconductivity, and hardness of Ag-4wt% TiB2 contact materials are increased with decreasing the Ag powder size. Furthermore, the Ag-4wt% TiB2 contact materials prepared from fine Ag powder have longer arc duration, larger erosion area, and shallower erosion pit, suggesting that the fine Ag powder is beneficial for arc dispersion and the improvement in arc erosion resistance.
The Ag-TiB2 contact materials with Ag powders of different sizes were prepared by spark plasma sintering. The relative density, electroconductivity, and hardness of Ag-4wt% TiB2 contact materials were measured, and the arc erosion behavior of the contact materials was analyzed under the vacuum condition. The surface morphologies of Ag-4wt% TiB2 contact materials after arc erosion were characterized by the scanning electron microscope. The arc duration was determined by the discharged waveform recorded by a Tektronix TDS-2014 dual channel digital memory oscilloscope, and the arc erosion mechanism was discussed. The results show that the relative density, electroconductivity, and hardness of Ag-4wt% TiB2 contact materials are increased with decreasing the Ag powder size. Furthermore, the Ag-4wt% TiB2 contact materials prepared from fine Ag powder have longer arc duration, larger erosion area, and shallower erosion pit, suggesting that the fine Ag powder is beneficial for arc dispersion and the improvement in arc erosion resistance.
2022, 51(3):772-777.
DOI: 10.12442/j.issn.1002-185X.20210022
Abstract:
The influence of Ag flake size on the electrical conductivity of silver pastes before and after folding was investigated. The low-temperature curing conductive silver pastes with good electrical conductivity after folding were fabricated using Ag flake with different flake sizes. Then the silver pastes were screen-printed on the polyimide substrate and sintered at 140 °C to form the circuits. The electrical resistivity of the printed circuits was detected by micro-ohmmeter. In order to measure the flexibility of Ag circuits, the variance of electrical resistivity of Ag circuits was detected after they were folded. The surface morphology of the folded Ag circuits was observed by the scanning electron microscopy. The conductive mechanism was analyzed. The results show that the small Ag flakes can act as the bridge between the unconnected flakes and fill the gaps after the circuits are folded, which forms the conductive networks, thereby improving the electrical conductivity after folding.
The influence of Ag flake size on the electrical conductivity of silver pastes before and after folding was investigated. The low-temperature curing conductive silver pastes with good electrical conductivity after folding were fabricated using Ag flake with different flake sizes. Then the silver pastes were screen-printed on the polyimide substrate and sintered at 140 °C to form the circuits. The electrical resistivity of the printed circuits was detected by micro-ohmmeter. In order to measure the flexibility of Ag circuits, the variance of electrical resistivity of Ag circuits was detected after they were folded. The surface morphology of the folded Ag circuits was observed by the scanning electron microscopy. The conductive mechanism was analyzed. The results show that the small Ag flakes can act as the bridge between the unconnected flakes and fill the gaps after the circuits are folded, which forms the conductive networks, thereby improving the electrical conductivity after folding.
2022, 51(3):778-782.
DOI: 10.12442/j.issn.1002-185X.20210062
Abstract:
In order to explore the loading mechanism and loading kinetics of TiO2 on cordierite, the acid-etched cordierite was used as the matrix and the TiO2 loading test was conducted by the chemical vapor deposition (CVD) method. The scanning electron microscope, energy disperse spectroscope, X-ray diffraction, and Brunauer-Emmett-Teller (BET) specific surface area measurement were used to characterize the TiO2 on cordierite surface and determine the loading speed at different temperatures. The results show that the surface of modified cordierite with TiO2 mainly consists of (211)-oriented and (200)-oriented anatase-TiO2 which is the octahedron and cube with BET specific surface area of 78.80 m2·g-1, an average pore diameter of 9.80 nm, and a bimodal distribution. The loading process is the diffusion and adsorption of TiCl4 and O2 towards the cordierite matrix. TiCl4 decomposes and Ti4+ enters the matrix lattice under the high oxygen potential to form TiO2 nuclei. After the preferential orientation and epitaxial growth, the loading deposition rate equation is
In order to explore the loading mechanism and loading kinetics of TiO2 on cordierite, the acid-etched cordierite was used as the matrix and the TiO2 loading test was conducted by the chemical vapor deposition (CVD) method. The scanning electron microscope, energy disperse spectroscope, X-ray diffraction, and Brunauer-Emmett-Teller (BET) specific surface area measurement were used to characterize the TiO2 on cordierite surface and determine the loading speed at different temperatures. The results show that the surface of modified cordierite with TiO2 mainly consists of (211)-oriented and (200)-oriented anatase-TiO2 which is the octahedron and cube with BET specific surface area of 78.80 m2·g-1, an average pore diameter of 9.80 nm, and a bimodal distribution. The loading process is the diffusion and adsorption of TiCl4 and O2 towards the cordierite matrix. TiCl4 decomposes and Ti4+ enters the matrix lattice under the high oxygen potential to form TiO2 nuclei. After the preferential orientation and epitaxial growth, the loading deposition rate equation is
2022, 51(3):783-792.
DOI: 10.12442/j.issn.1002-185X.20210065
Abstract:
The thermal fatigue properties of multicomponent Al-7Si-0.3Mg aluminum alloys in three different treatment states at different temperatures were studied. The integral method and secant method were proposed to calculate the thermal fatigue crack propagation life, and the thermal fatigue crack growth behavior of the alloys was analyzed. The results indicate that the temperature change has a direct effect on the thermal fatigue crack propagation rate of the multicomponent Al-7Si-0.3Mg aluminum alloys. The thermal fatigue properties of the multicomponent Al-7Si-0.3Mg alloys with addition of Cu, Mn, Ti, and other elements after refinement and direct refinement are superior to those of the as-cast Al-7Si-0.3Mg alloys. The growth behavior of thermal fatigue cracks mainly includes the initiation and propagation of thermal cracks. The initiation of thermal fatigue crack requires a certain incubation period and the crack is generated at the V-notch. When the alternating thermal stress exceeds the yield strength σs of alloys, different types of thermal fatigue cracks appear at the stress concentration parts or at defects of the V-notch but with only one main crack. When the angle between the crack tip propagation path and the major axis direction of the second phase particle is less than 45°, the crack propagation extends further along the edge of the second phase particles; when the angle between the crack tip propagation path and the minor axis direction of the second phase particle is less than 45°, the crack passes through the second phase particle and extends forward.
The thermal fatigue properties of multicomponent Al-7Si-0.3Mg aluminum alloys in three different treatment states at different temperatures were studied. The integral method and secant method were proposed to calculate the thermal fatigue crack propagation life, and the thermal fatigue crack growth behavior of the alloys was analyzed. The results indicate that the temperature change has a direct effect on the thermal fatigue crack propagation rate of the multicomponent Al-7Si-0.3Mg aluminum alloys. The thermal fatigue properties of the multicomponent Al-7Si-0.3Mg alloys with addition of Cu, Mn, Ti, and other elements after refinement and direct refinement are superior to those of the as-cast Al-7Si-0.3Mg alloys. The growth behavior of thermal fatigue cracks mainly includes the initiation and propagation of thermal cracks. The initiation of thermal fatigue crack requires a certain incubation period and the crack is generated at the V-notch. When the alternating thermal stress exceeds the yield strength σs of alloys, different types of thermal fatigue cracks appear at the stress concentration parts or at defects of the V-notch but with only one main crack. When the angle between the crack tip propagation path and the major axis direction of the second phase particle is less than 45°, the crack propagation extends further along the edge of the second phase particles; when the angle between the crack tip propagation path and the minor axis direction of the second phase particle is less than 45°, the crack passes through the second phase particle and extends forward.
2022, 51(3):793-799.
DOI: 10.12442/j.issn.1002-185X.20201000
Abstract:
The ceria-stabilized zirconia (CSZ) coating with an excellent hydrogen resistance performance was prepared by micro-arc oxidation (MAO) with cerium addition. The thickness, bonding strength, morphology, phase structure, chemical valence, and hydrogen resistance of ceramic coatings were investigated by coating thickness gauge, auto-scratch tester, scanning electron microscopy, energy dispersive X-ray spectrometer, X-ray diffraction, and X-ray photoelectron spectroscopy, and vacuum dehydrogenation experiment. Results show that CSZ ceramic coatings are mainly composed of monoclinic zirconia (m-ZrO2), tetragonal zirconia (t-ZrO2), and t-Zr0.82Ce0.18O2. With increasing the cerium content, the thickness of coating is increased. When the cerium content is 9mol%, the thickness of CSZ ceramic coating reaches the maximum of 135.5 μm, the bonding force is 52.46 N, and the hydrogen permeation reduction factor (PRF) is 19, which indicates an excellent hydrogen resistance. The cerium addition inhibits the phase transformation from t-ZrO2 to m-ZrO2, thereby promoting the formation of stable t-ZrO2 at elevated temperatures.
The ceria-stabilized zirconia (CSZ) coating with an excellent hydrogen resistance performance was prepared by micro-arc oxidation (MAO) with cerium addition. The thickness, bonding strength, morphology, phase structure, chemical valence, and hydrogen resistance of ceramic coatings were investigated by coating thickness gauge, auto-scratch tester, scanning electron microscopy, energy dispersive X-ray spectrometer, X-ray diffraction, and X-ray photoelectron spectroscopy, and vacuum dehydrogenation experiment. Results show that CSZ ceramic coatings are mainly composed of monoclinic zirconia (m-ZrO2), tetragonal zirconia (t-ZrO2), and t-Zr0.82Ce0.18O2. With increasing the cerium content, the thickness of coating is increased. When the cerium content is 9mol%, the thickness of CSZ ceramic coating reaches the maximum of 135.5 μm, the bonding force is 52.46 N, and the hydrogen permeation reduction factor (PRF) is 19, which indicates an excellent hydrogen resistance. The cerium addition inhibits the phase transformation from t-ZrO2 to m-ZrO2, thereby promoting the formation of stable t-ZrO2 at elevated temperatures.
2022, 51(3):800-805.
DOI: 10.12442/j.issn.1002-185X.20210048
Abstract:
The effect of ultrasonic vibration coupled with direct current on the wetting behavior of Sn liquid solder on Cu substrate at 270 °C was studied by the wetting balance technique. The wetting balance curves were measured. Results show that the ultrasonic vibration coupled with direct current method significantly improves the wettability of Sn liquid solder. With increasing the ultrasonic vibration power and direct current, the maximum equilibrium wetting force is increased. According to the microstructure observations of interface during wetting process, the ultrasonic vibration coupled with direct current method can increase the dissolution of Cu substrate in the molten Sn solder and promote the precipitation of the intermetallic compounds at interface. The sound pressure distribution inside the molten Sn solder was simulated by a finite element software. The maximum sound pressure occurs at the front end of the ultrasonic probe. During the ultrasonic vibration coupled with direct current process, the chemical driving force caused by the precipitation of intermetallic compounds at interface and the strong convection inside the molten Sn solder jointly promote the movement of the triple-phase line, thereby improving the wettability of Sn solder.
The effect of ultrasonic vibration coupled with direct current on the wetting behavior of Sn liquid solder on Cu substrate at 270 °C was studied by the wetting balance technique. The wetting balance curves were measured. Results show that the ultrasonic vibration coupled with direct current method significantly improves the wettability of Sn liquid solder. With increasing the ultrasonic vibration power and direct current, the maximum equilibrium wetting force is increased. According to the microstructure observations of interface during wetting process, the ultrasonic vibration coupled with direct current method can increase the dissolution of Cu substrate in the molten Sn solder and promote the precipitation of the intermetallic compounds at interface. The sound pressure distribution inside the molten Sn solder was simulated by a finite element software. The maximum sound pressure occurs at the front end of the ultrasonic probe. During the ultrasonic vibration coupled with direct current process, the chemical driving force caused by the precipitation of intermetallic compounds at interface and the strong convection inside the molten Sn solder jointly promote the movement of the triple-phase line, thereby improving the wettability of Sn solder.
Yu Zhuhuan
,
Fei Zhenbao
,
Yan Yawen
,
Qiang Junfeng
,
Gao Wei
,
Wang Xiaohui
,
Liu Xuliang
,
Yi Dawei
2022, 51(3):806-813.
DOI: 10.12442/j.issn.1002-185X.20210017
Abstract:
The effect of different solution treatments on the microstructure and element segregation of AM3 nickel-based single crystal superalloys with the carbon content of 0.045wt% was investigated. The optical microscope (OM) and scanning electron microscope (SEM) were used to observe the microstructure and γ' phase of AM3 superalloys, and the electron-probe microanalysis (EPMA) was used to analyze the element segregation. The results show that the incipient melting temperature of the AM3 superalloys is 1305 °C. After the solution treatment of 1305 °C/6 h following the homogenization treatment of 1300 °C/3 h, the incipient melting structure is reduced, and the incipient melting temperature is increased by about 5 °C. With increasing the solution temperature and prolonging the solution duration, the volume fraction and size of the precipitated γ' phase are increased significantly, and the segregation ratio of Cr, Co, Mo, W, and Al elements is closer to 1. The existence of incipient melting structure prevents the segregation of Ti in AM3 superalloys with prolonging the solution duration after heat treatment. Thus, the optimum heat treatment process is 1300 °C/3 h+1305 °C/6 h/air cooling (AC)+1080 °C/6 h+870 °C/20 h/AC. The dendrite structure of AM3 single crystal superalloys completely disappear after heat treatment. The cubic degree of γ' phase is improved, the size of γ' phase reaches 454 nm, the volume fraction of γ' phase is 66.05vol%, and the segregation of Cr, Co, Mo, W, Al, and Ti elements is significantly reduced.
The effect of different solution treatments on the microstructure and element segregation of AM3 nickel-based single crystal superalloys with the carbon content of 0.045wt% was investigated. The optical microscope (OM) and scanning electron microscope (SEM) were used to observe the microstructure and γ' phase of AM3 superalloys, and the electron-probe microanalysis (EPMA) was used to analyze the element segregation. The results show that the incipient melting temperature of the AM3 superalloys is 1305 °C. After the solution treatment of 1305 °C/6 h following the homogenization treatment of 1300 °C/3 h, the incipient melting structure is reduced, and the incipient melting temperature is increased by about 5 °C. With increasing the solution temperature and prolonging the solution duration, the volume fraction and size of the precipitated γ' phase are increased significantly, and the segregation ratio of Cr, Co, Mo, W, and Al elements is closer to 1. The existence of incipient melting structure prevents the segregation of Ti in AM3 superalloys with prolonging the solution duration after heat treatment. Thus, the optimum heat treatment process is 1300 °C/3 h+1305 °C/6 h/air cooling (AC)+1080 °C/6 h+870 °C/20 h/AC. The dendrite structure of AM3 single crystal superalloys completely disappear after heat treatment. The cubic degree of γ' phase is improved, the size of γ' phase reaches 454 nm, the volume fraction of γ' phase is 66.05vol%, and the segregation of Cr, Co, Mo, W, Al, and Ti elements is significantly reduced.
2022, 51(3):814-820.
DOI: 10.12442/j.issn.1002-185X.20210016
Abstract:
The NiAl coating was prepared on the surface of NiCrW-based superalloy by pack cementation method with CaCl2 as an activator. The surface and cross-section of the coated specimens were analyzed via X-ray diffraction and scanning electron microscopy coupled with energy dispersive spectroscopy. Results show that CaCl2 can replace NH4Cl as an effective activator. The NiAl coating with an almost single phase structure and a thickness of 30 μm can be obtained after pack cementation at 950 °C for 4 h. A chromium-rich interlayer can be observed between the NiAl coating and the substrate. When the filling ratio of the pack powder is less than 100%, the needle-like θ-Al2O3 phase is formed on the NiAl layer surface. During the constant temperature air oxidation test at 1000 °C, the NiAl coating suffers from high speed oxidation to slow speed oxidation, which is in agreement with the phase transformation from needle-like metastable θ-Al2O3 to irregular granular stable α-Al2O3. The final stable α-Al2O3 provides a good oxidation resistance for the substrate.
The NiAl coating was prepared on the surface of NiCrW-based superalloy by pack cementation method with CaCl2 as an activator. The surface and cross-section of the coated specimens were analyzed via X-ray diffraction and scanning electron microscopy coupled with energy dispersive spectroscopy. Results show that CaCl2 can replace NH4Cl as an effective activator. The NiAl coating with an almost single phase structure and a thickness of 30 μm can be obtained after pack cementation at 950 °C for 4 h. A chromium-rich interlayer can be observed between the NiAl coating and the substrate. When the filling ratio of the pack powder is less than 100%, the needle-like θ-Al2O3 phase is formed on the NiAl layer surface. During the constant temperature air oxidation test at 1000 °C, the NiAl coating suffers from high speed oxidation to slow speed oxidation, which is in agreement with the phase transformation from needle-like metastable θ-Al2O3 to irregular granular stable α-Al2O3. The final stable α-Al2O3 provides a good oxidation resistance for the substrate.
Yang Liangwei
,
Chen Haoran
,
Jin Xin
,
Liu Wei
,
Yu Xinmin
,
Liu Junpeng
,
Song Huanjun
,
Li Xiaodong
,
Yu Yi
,
Wang Peng
,
Zhang Baopeng
2022, 51(3):821-826.
DOI: 10.12442/j.issn.1002-185X.20210067
Abstract:
Through the modified household microwave oven system, the graphene-based nanocomposites were in-situ and efficiently synthesized. Results show that the graphene nanosheets can be uniformly generated on the surface of the commercial anatase TiO2 nanoparticles by microwave-assisted method in a few minutes (the minimum duration is 3 min) through the acute corona discharge of SiO2/Si. The size of graphene nanosheet is about 50 nm, and few defects can be observed. The crystal structure of anatase TiO2 remains due to the short production period and low synthesis temperature (600~700 °C). The excellent electrical conductivity of graphene can improve the Li ion diffusion and the electron transport, and decrease the contact resistance at the interface of electrode/electrolyte. The as-prepared graphene/TiO2 nanocomposite electrode shows a two-fold increase of capacity with good cycling stability under the condition of 1 C (170 mA·g-1), compared with the traditional TiO2 nanoparticles. The specific capacity gap of graphene/TiO2 nanocomposite is substantially widened under different charge-discharge rates (1~5 C), compared with that of the commercial anatase TiO2 nanoparticles.
Through the modified household microwave oven system, the graphene-based nanocomposites were in-situ and efficiently synthesized. Results show that the graphene nanosheets can be uniformly generated on the surface of the commercial anatase TiO2 nanoparticles by microwave-assisted method in a few minutes (the minimum duration is 3 min) through the acute corona discharge of SiO2/Si. The size of graphene nanosheet is about 50 nm, and few defects can be observed. The crystal structure of anatase TiO2 remains due to the short production period and low synthesis temperature (600~700 °C). The excellent electrical conductivity of graphene can improve the Li ion diffusion and the electron transport, and decrease the contact resistance at the interface of electrode/electrolyte. The as-prepared graphene/TiO2 nanocomposite electrode shows a two-fold increase of capacity with good cycling stability under the condition of 1 C (170 mA·g-1), compared with the traditional TiO2 nanoparticles. The specific capacity gap of graphene/TiO2 nanocomposite is substantially widened under different charge-discharge rates (1~5 C), compared with that of the commercial anatase TiO2 nanoparticles.
Zheng Jingwu
,
Chen Yishun
,
Fu Yongcheng
,
Zhang Shuan
,
Qiao Liang
,
Cai Wei
,
Tang Yiping
,
Yi Xiaofei
,
Chen Jingwu
,
Li Wangchang
,
Ying Yao
,
Yu Jing
,
Liu Youhao
,
Huang Xiulian
,
Che Shenglei
2022, 51(3):827-834.
DOI: 10.12442/j.issn.1002-185X.20210040
Abstract:
The nanocrystalline Cu protective coating was obtained on the Nd-Fe-B magnet matrix in the cyanide-free electrolyte by the ultrasonic-assisted electrodeposition under high cathodic current density. The coating morphology, crystallite size, microhardness, and corrosion resistance of the Cu coatings were analyzed under different ultrasonic frequencies. Results show that with increasing the ultrasonic frequency, the effective cathodic current density of Cu electrodeposition in the complex electroplating solution system is increased remarkably, and the corresponding current efficiency is enhanced, thereby achieving the dense nanocrystalline Cu coating. Under the condition of the cathodic current density of 4.0 A·dm-2 and frequency of 40 kHz, the Cu coating with the crystallite of 18.8 nm in size can be obtained. The bonding strength between the Cu coating and sintered Nd-Fe-B matrix is improved via ultrasonic-assisted electrodeposition which promotes the electrodeposition in the blind holes of Nd-Fe-B matrix. The corrosion resistance of Cu-coated Nd-Fe-B materials with the same coating thickness is improved gradually with increasing the ultrasonic frequency.
The nanocrystalline Cu protective coating was obtained on the Nd-Fe-B magnet matrix in the cyanide-free electrolyte by the ultrasonic-assisted electrodeposition under high cathodic current density. The coating morphology, crystallite size, microhardness, and corrosion resistance of the Cu coatings were analyzed under different ultrasonic frequencies. Results show that with increasing the ultrasonic frequency, the effective cathodic current density of Cu electrodeposition in the complex electroplating solution system is increased remarkably, and the corresponding current efficiency is enhanced, thereby achieving the dense nanocrystalline Cu coating. Under the condition of the cathodic current density of 4.0 A·dm-2 and frequency of 40 kHz, the Cu coating with the crystallite of 18.8 nm in size can be obtained. The bonding strength between the Cu coating and sintered Nd-Fe-B matrix is improved via ultrasonic-assisted electrodeposition which promotes the electrodeposition in the blind holes of Nd-Fe-B matrix. The corrosion resistance of Cu-coated Nd-Fe-B materials with the same coating thickness is improved gradually with increasing the ultrasonic frequency.
2022, 51(3):835-842.
DOI: 10.12442/j.issn.1002-185X.20210055
Abstract:
The surface gradient nanocrystalline structure was fabricated by the surface mechanical attrition treatment (SMAT), and the influence of surface nanocrystallization on the surface microstructure and characteristic of passive film on pure titanium was studied. The anodic oxidation was conducted in 0.5 mol/L H2SO4 solution under the potentiostatic mode at 30 V for different durations to investigate the surface characteristic and corrosion resistance of the passive films by optical microscope, X-ray diffraction, Raman spectrometer, X-ray photoelectron spectroscopy, and electrochemical test. The results show that the gradient nanocrystalline structure can increase the film thickness, promote the crystallization, and improve the corrosion resistance of passive film. The influence mechanism of surface nanocrystallization on the corrosion resistance can be explained by the cation-anion-vacancy condensation.
The surface gradient nanocrystalline structure was fabricated by the surface mechanical attrition treatment (SMAT), and the influence of surface nanocrystallization on the surface microstructure and characteristic of passive film on pure titanium was studied. The anodic oxidation was conducted in 0.5 mol/L H2SO4 solution under the potentiostatic mode at 30 V for different durations to investigate the surface characteristic and corrosion resistance of the passive films by optical microscope, X-ray diffraction, Raman spectrometer, X-ray photoelectron spectroscopy, and electrochemical test. The results show that the gradient nanocrystalline structure can increase the film thickness, promote the crystallization, and improve the corrosion resistance of passive film. The influence mechanism of surface nanocrystallization on the corrosion resistance can be explained by the cation-anion-vacancy condensation.
2022, 51(3):843-849.
DOI: 10.12442/j.issn.1002-185X.20210013
Abstract:
Superplasticity of TA15 alloy was investigated based on the variable strain rate sensitivity exponent m value method. The superplastic tensile tests were conducted at 1053~1223 K. Results show that the elongation of TA15 alloy is 580%~1922%. The microstructure analysis shows that the grains are coarsened with increasing the temperatures but remain the equiaxed structure during the deformation. In addition, the phase transformation α→β occurs at 1223 K, resulting in the serious reduction in superplastic property. Compared with that treated by the constant strain rate method, the superplasticity of TA15 alloy treated by the variable m value method is greatly enhanced. During the superplastic deformation, the mechanical properties and microstructure evolution are in good agreement with the Ashby-Verrall model. Therefore, it can be inferred that the dominant superplastic mechanism for TA15 alloy based on variable m value method is the grain boundary glide accommodated by diffusion creep.
Superplasticity of TA15 alloy was investigated based on the variable strain rate sensitivity exponent m value method. The superplastic tensile tests were conducted at 1053~1223 K. Results show that the elongation of TA15 alloy is 580%~1922%. The microstructure analysis shows that the grains are coarsened with increasing the temperatures but remain the equiaxed structure during the deformation. In addition, the phase transformation α→β occurs at 1223 K, resulting in the serious reduction in superplastic property. Compared with that treated by the constant strain rate method, the superplasticity of TA15 alloy treated by the variable m value method is greatly enhanced. During the superplastic deformation, the mechanical properties and microstructure evolution are in good agreement with the Ashby-Verrall model. Therefore, it can be inferred that the dominant superplastic mechanism for TA15 alloy based on variable m value method is the grain boundary glide accommodated by diffusion creep.
Su Xin
,
Shen Shanzhong
,
Xu Jibo
,
Kuang Xinwen
,
Lu Yiqi
,
Yang Chao
,
Zhang Fa
,
Long Haibo
,
Tian Xitian
2022, 51(3):850-857.
DOI: 10.12442/j.issn.1002-185X.20210036
Abstract:
The microstructure and thermal formability of twin-roll cast 7075 alloy strips prepared with and without electrical pulse (EP) of 5 mm in thickness were investigated by hot tensile tests under the condition of deformation temperature of 250~350 °C and strain rate of 0.001~0.01 s-1. The related EP current parameters are as follows: the single cycle pulse width is 0.005 s; the pulse peak current is 300 A. The results show that the EP current effectively promotes the grain refinement and the precipitate homogeneousness, because the electromagnetic oscillation enhances the solute mixing ability during solidification. Meanwhile, the rolling textures of face-centered cubic (fcc) 7075 Al strips have the {423}<144> orientation. After EP current modification, the orientation of 7075 Al strips is {421}<216>. The peak flow stress of the 7075 alloy strips prepared with EP current is about 1.1~1.3 times larger than that of the original 7075 alloy strips. The electron back-scattered diffraction analysis shows that EP current can effectively improve the preferred distribution of the grains by promoting the dynamic recrystallization. Furthermore, the hyperbolic sine equation and the constitutive model with Zener-Holloman parameter are established based on the analyses. Besides, according to the fracture morphology, the EP current is beneficial to improve the mechanical properties of 7075 alloys at elevated temperature. Finally, the processing maps are established and the proper hot working parameters are designed as the temperature range of 290~330 °C and the strain rate of 0.001~0.002 s-1.
The microstructure and thermal formability of twin-roll cast 7075 alloy strips prepared with and without electrical pulse (EP) of 5 mm in thickness were investigated by hot tensile tests under the condition of deformation temperature of 250~350 °C and strain rate of 0.001~0.01 s-1. The related EP current parameters are as follows: the single cycle pulse width is 0.005 s; the pulse peak current is 300 A. The results show that the EP current effectively promotes the grain refinement and the precipitate homogeneousness, because the electromagnetic oscillation enhances the solute mixing ability during solidification. Meanwhile, the rolling textures of face-centered cubic (fcc) 7075 Al strips have the {423}<144> orientation. After EP current modification, the orientation of 7075 Al strips is {421}<216>. The peak flow stress of the 7075 alloy strips prepared with EP current is about 1.1~1.3 times larger than that of the original 7075 alloy strips. The electron back-scattered diffraction analysis shows that EP current can effectively improve the preferred distribution of the grains by promoting the dynamic recrystallization. Furthermore, the hyperbolic sine equation and the constitutive model with Zener-Holloman parameter are established based on the analyses. Besides, according to the fracture morphology, the EP current is beneficial to improve the mechanical properties of 7075 alloys at elevated temperature. Finally, the processing maps are established and the proper hot working parameters are designed as the temperature range of 290~330 °C and the strain rate of 0.001~0.002 s-1.
2022, 51(3):858-865.
DOI: 10.12442/j.issn.1002-185X.20210020
Abstract:
The Mg-10Gd-3Y-1Sn alloys were prepared by centrifugal casting and hot rolling, and their microstructure and mechanical properties were investigated by X-ray diffraction, optical microscope, scanning electron microscope, and tensile tests. Results show that the centrifugal-cast Mg-10Gd-3Y-1Sn alloy consists of α-Mg, Mg24(Gd,Y)5, Mg2(Sn,Y)3Gd2, and Mg3(Gd,Y) phases. With increasing the centrifugal radius and rotation speed, the tensile strength of alloys is increased gradually due to the decreased grain size of alloys. The ultimate tensile strength of as-rolled alloys after centrifugal casting with the rotation speed of 700 r/min is 304 and 296 MPa at room temperature and 300 °C, respectively. The improved tensile strength of Mg-10Gd-3Y-1Sn alloy at elevated temperatures mainly results from the Mg24(Gd, Y)5, Mg2(Sn, Y)3Gd2, and Mg3(Gd, Y) phases with excellent thermal stability.
The Mg-10Gd-3Y-1Sn alloys were prepared by centrifugal casting and hot rolling, and their microstructure and mechanical properties were investigated by X-ray diffraction, optical microscope, scanning electron microscope, and tensile tests. Results show that the centrifugal-cast Mg-10Gd-3Y-1Sn alloy consists of α-Mg, Mg24(Gd,Y)5, Mg2(Sn,Y)3Gd2, and Mg3(Gd,Y) phases. With increasing the centrifugal radius and rotation speed, the tensile strength of alloys is increased gradually due to the decreased grain size of alloys. The ultimate tensile strength of as-rolled alloys after centrifugal casting with the rotation speed of 700 r/min is 304 and 296 MPa at room temperature and 300 °C, respectively. The improved tensile strength of Mg-10Gd-3Y-1Sn alloy at elevated temperatures mainly results from the Mg24(Gd, Y)5, Mg2(Sn, Y)3Gd2, and Mg3(Gd, Y) phases with excellent thermal stability.
2022, 51(3):866-872.
DOI: 10.12442/j.issn.1002-185X.20210025
Abstract:
According to the self-consistent bond length difference (SCBLD) method based on the empirical electron theory of solids and molecules, namely the Yu Ruihuang electron theory, the valence electron structure parameters (VESPs) were calculated to characterize the properties of alloy phases, and to investigate the influence of alloying elements (Al, Sn, Ti, Hf, V, Mo, Nb, Cu, Fe, Cr, Ni, Pd, and Re) on the phase transformation temperature of zirconium alloys. The results show that the sum of cohesive energy (
According to the self-consistent bond length difference (SCBLD) method based on the empirical electron theory of solids and molecules, namely the Yu Ruihuang electron theory, the valence electron structure parameters (VESPs) were calculated to characterize the properties of alloy phases, and to investigate the influence of alloying elements (Al, Sn, Ti, Hf, V, Mo, Nb, Cu, Fe, Cr, Ni, Pd, and Re) on the phase transformation temperature of zirconium alloys. The results show that the sum of cohesive energy (
16 Thermo-structural Simulation and Ablation Behavior of 3D C/C Composites Throat in Solid Rocket Motor
2022, 51(3):873-880.
DOI: 10.12442/j.issn.1002-185X.20210028
Abstract:
The heat transfer coefficient, temperature distribution, and stress distribution of 3D carbon/carbon (C/C) composite solid rocket motor (SRM) throat at the thermal equilibrium state were calculated through the comprehensive thermo-structural simulation, and SRM used the tri-component propellant of ammonium perchlorate/hydroxyl-terminated polybutadiene/Al under the condition of 6.5 MPa for long run of 20, 60, and 95 s. The analysis of ablation behavior and mechanism of different throat regions was also conducted according to the simulation results. The results show that the temperature at throat convergent zone is the highest due to the thermochemical ablation between the oxidation components (H2O, CO2, H2) and the surface carbon. The central throat zone has the maximum heat transfer coefficient with relatively high temperature. The ablation in the central throat zone is the most severe due to the stress of inner surface, including the gas thermochemical ablation, high-speed-flow mechanical denudation, and particle erosion. The central throat surface has small grooves or cracks, and the throat tends to decompose due to the stress and oxidation. The stress and temperature of throat exit zone are decreased, and the ablation rate is obviously reduced. The throat ablation mechanism is the combination effect of thermochemical ablation of oxidation components and the carbon influenced by the stress and temperature, flow mechanical denudation, and Al2O3 particle erosion.
The heat transfer coefficient, temperature distribution, and stress distribution of 3D carbon/carbon (C/C) composite solid rocket motor (SRM) throat at the thermal equilibrium state were calculated through the comprehensive thermo-structural simulation, and SRM used the tri-component propellant of ammonium perchlorate/hydroxyl-terminated polybutadiene/Al under the condition of 6.5 MPa for long run of 20, 60, and 95 s. The analysis of ablation behavior and mechanism of different throat regions was also conducted according to the simulation results. The results show that the temperature at throat convergent zone is the highest due to the thermochemical ablation between the oxidation components (H2O, CO2, H2) and the surface carbon. The central throat zone has the maximum heat transfer coefficient with relatively high temperature. The ablation in the central throat zone is the most severe due to the stress of inner surface, including the gas thermochemical ablation, high-speed-flow mechanical denudation, and particle erosion. The central throat surface has small grooves or cracks, and the throat tends to decompose due to the stress and oxidation. The stress and temperature of throat exit zone are decreased, and the ablation rate is obviously reduced. The throat ablation mechanism is the combination effect of thermochemical ablation of oxidation components and the carbon influenced by the stress and temperature, flow mechanical denudation, and Al2O3 particle erosion.
2022, 51(3):881-887.
DOI: 10.12442/j.issn.1002-185X.20210616
Abstract:
The molecular dynamics method was applied to simulate the effects of substrate surface morphology on nano-thermal spraying. The effects of columnar rough surface and smooth surface on cluster flattening, defect evolution of substrate, stress distribution, and the bonding strength between coating and substrate were investigated. The results show that the substrate surface morphology has a significant effect on the bonding strength of thermal spraying. The rough surface increases the actual contact area between the clusters and the matrix, improves the adhesion, causes the anchorage effect at the interface, and thereby enhances the bonding strength. In addition, the substrate surface morphology can change the stress distribution in the interface region. The columnar rough surface on the matrix weakens the stress concentration effect, decreases the critical stress, and reduces the damage to the substrate. Besides, the rough surface hinders the cluster slip and reduces the flattening ratio.
The molecular dynamics method was applied to simulate the effects of substrate surface morphology on nano-thermal spraying. The effects of columnar rough surface and smooth surface on cluster flattening, defect evolution of substrate, stress distribution, and the bonding strength between coating and substrate were investigated. The results show that the substrate surface morphology has a significant effect on the bonding strength of thermal spraying. The rough surface increases the actual contact area between the clusters and the matrix, improves the adhesion, causes the anchorage effect at the interface, and thereby enhances the bonding strength. In addition, the substrate surface morphology can change the stress distribution in the interface region. The columnar rough surface on the matrix weakens the stress concentration effect, decreases the critical stress, and reduces the damage to the substrate. Besides, the rough surface hinders the cluster slip and reduces the flattening ratio.
2022, 51(3):888-894.
DOI: 10.12442/j.issn.1002-185X.20210031
Abstract:
The compression deformation behavior of 316LN austenitic stainless steel was investigated at 1050~1200 °C under strain rate of 0.1, 1, 50 s-1. The influence of deformation temperature and strain rate on the hot flow curves was analyzed. Based on the dislocation density theory, the hot deformation constitutive model of 316LN steel was established. The softening mechanism of the 316LN steel was revealed. The results show that the dynamic recrystallization (DRX) dominates the softening mechanism under the condition of high temperature and low strain rate (<0.1 s-1); the dynamic recovery (DRV) dominates the softening mechanism under the condition of high temperature and high strain rate (>1 s-1); DRX and DRV dominate the softening mechanism under the condition of high temperature and strain rate of 0.1, 1 s-1. The established constitutive model can precisely predict the hot deformation behavior of 316LN steel: its Pearson correlation coefficient is 0.9956 and the average absolute value of relative error is 3.07%, indicating the accuracy of this constitutive model.
The compression deformation behavior of 316LN austenitic stainless steel was investigated at 1050~1200 °C under strain rate of 0.1, 1, 50 s-1. The influence of deformation temperature and strain rate on the hot flow curves was analyzed. Based on the dislocation density theory, the hot deformation constitutive model of 316LN steel was established. The softening mechanism of the 316LN steel was revealed. The results show that the dynamic recrystallization (DRX) dominates the softening mechanism under the condition of high temperature and low strain rate (<0.1 s-1); the dynamic recovery (DRV) dominates the softening mechanism under the condition of high temperature and high strain rate (>1 s-1); DRX and DRV dominate the softening mechanism under the condition of high temperature and strain rate of 0.1, 1 s-1. The established constitutive model can precisely predict the hot deformation behavior of 316LN steel: its Pearson correlation coefficient is 0.9956 and the average absolute value of relative error is 3.07%, indicating the accuracy of this constitutive model.
2022, 51(3):895-905.
DOI: 10.12442/j.issn.1002-185X.20210246
Abstract:
The corrosion behavior of Cu-4wt.%Ti alloy in solid solution in simulated polluted seawater (3.5wt.% NaCl solution containing S2-) was studied by immersion test and electrochemical test.Scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to test and analyze the corrosion products on the surface of copper titanium alloy.The results show that the Cl- causes pitting corrosion of Cu-Ti alloy in solution, and the pitting pits with uniform distribution are smaller in size. When the concentration of S2- in NaCl solution is 60ppm, the pitting pits are connected with each other on the surface of the alloy, showing uniform corrosion morphology.There is competitive adsorption between S2- and Cl- on the corrosion of Cu-Ti alloy, and S2- Corrosion of copper-titanium alloy is severe due to its strong adsorption.In NaCl solution containing S2-, the corrosion products are mainly CuS, Cu2S, Cu2O and Cu2(OH)3Cl.When S2- concentration is high, the concentration of OH- in the solution will increase, which will increase the thickness and density of the corrosion product film. Therefore, when S2- concentration reaches 100ppm, passivation can occur to the Cu-Ti alloy to slow down the corrosion. Key words: Cu-Ti alloy; S2- pollution; Simulated sea water; Corrosion; Competitive adsorption
The corrosion behavior of Cu-4wt.%Ti alloy in solid solution in simulated polluted seawater (3.5wt.% NaCl solution containing S2-) was studied by immersion test and electrochemical test.Scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to test and analyze the corrosion products on the surface of copper titanium alloy.The results show that the Cl- causes pitting corrosion of Cu-Ti alloy in solution, and the pitting pits with uniform distribution are smaller in size. When the concentration of S2- in NaCl solution is 60ppm, the pitting pits are connected with each other on the surface of the alloy, showing uniform corrosion morphology.There is competitive adsorption between S2- and Cl- on the corrosion of Cu-Ti alloy, and S2- Corrosion of copper-titanium alloy is severe due to its strong adsorption.In NaCl solution containing S2-, the corrosion products are mainly CuS, Cu2S, Cu2O and Cu2(OH)3Cl.When S2- concentration is high, the concentration of OH- in the solution will increase, which will increase the thickness and density of the corrosion product film. Therefore, when S2- concentration reaches 100ppm, passivation can occur to the Cu-Ti alloy to slow down the corrosion. Key words: Cu-Ti alloy; S2- pollution; Simulated sea water; Corrosion; Competitive adsorption
2022, 51(3):906-912.
DOI: 10.12442/j.issn.1002-185X.20210228
Abstract:
Phase equilibria in the Zr-rich region of Zr-Fe-Si system at 580 ℃ was determined through equilibrated alloy method by using X-ray powder diffraction (XRD), scanning electron microscope (SEM) and energy dispersive x-ray analysis (EDX). Five two-phase equilibria Zr2Si + Zr2Fe, Zr2Fe + ZrFe2, Zr2Fe + Zr3Fe, Zr2Si + Zr5Si3, α-Zr + Zr2Si and two three-phase equilibria α-Zr + Zr2Fe + Zr3Fe, α-Zr + Zr2Si + Zr5Si3 were included in this study. The compounds Zr2Fe and Zr5Si3 which were marked as unstable phases at 580 ℃ in the available Zr-Fe and Zr-Si phase diagrams were observed, While the compound Zr3Si which was marked as stable phase in the Zr-Si phase diagram was not observed in this work.. It was shown that Zr2Fe and Zr2Si with same crystal structure were partially miscible. Solubility of Fe in Zr2Si is up to 5.95 at.% and solubility of Si in Zr2Fe is up to 6.38 at.%. ZrFe2 (cubic crystal structure) dissolves 3.11 at.% of Si.
Phase equilibria in the Zr-rich region of Zr-Fe-Si system at 580 ℃ was determined through equilibrated alloy method by using X-ray powder diffraction (XRD), scanning electron microscope (SEM) and energy dispersive x-ray analysis (EDX). Five two-phase equilibria Zr2Si + Zr2Fe, Zr2Fe + ZrFe2, Zr2Fe + Zr3Fe, Zr2Si + Zr5Si3, α-Zr + Zr2Si and two three-phase equilibria α-Zr + Zr2Fe + Zr3Fe, α-Zr + Zr2Si + Zr5Si3 were included in this study. The compounds Zr2Fe and Zr5Si3 which were marked as unstable phases at 580 ℃ in the available Zr-Fe and Zr-Si phase diagrams were observed, While the compound Zr3Si which was marked as stable phase in the Zr-Si phase diagram was not observed in this work.. It was shown that Zr2Fe and Zr2Si with same crystal structure were partially miscible. Solubility of Fe in Zr2Si is up to 5.95 at.% and solubility of Si in Zr2Fe is up to 6.38 at.%. ZrFe2 (cubic crystal structure) dissolves 3.11 at.% of Si.
Baoquan Xue
,
Yaqian Yang
,
Tian liang
,
Bo chen
,
Yingche Ma
,
Kui Liu
,
Hongyi Shan
,
Taifeng Kang
,
Peiwen Gu
2022, 51(3):913-920.
DOI: 10.12442/j.issn.1002-185X.20210245
Abstract:
In order to simulate the transient phenomenon of retention in high temperature core melt of nuclear power plant, the mixture of 50kg ZrO2-Fe-Zr system was melted by electromagnetic induction in a cold crucible. The phase and element distribution of oxide layer, metal layer and oxide crust of solidified melt ingot were analyzed by means of XRD, SEM, EDS and so on. The results show that during the formation of the 50-kg-scale initial molten pool, the high temperature molten material is separated into a two-layer structure of metal layer and oxide layer due to gravity and incompatibility, and an oxidation crust is formed on and around the top of the molten pool; After that, due to the secondary feeding to form a three-layer molten pool with the top liquid metal, the top metal molten pool can gradually settle to the bottom of the molten pool through the oxide hard crust.
In order to simulate the transient phenomenon of retention in high temperature core melt of nuclear power plant, the mixture of 50kg ZrO2-Fe-Zr system was melted by electromagnetic induction in a cold crucible. The phase and element distribution of oxide layer, metal layer and oxide crust of solidified melt ingot were analyzed by means of XRD, SEM, EDS and so on. The results show that during the formation of the 50-kg-scale initial molten pool, the high temperature molten material is separated into a two-layer structure of metal layer and oxide layer due to gravity and incompatibility, and an oxidation crust is formed on and around the top of the molten pool; After that, due to the secondary feeding to form a three-layer molten pool with the top liquid metal, the top metal molten pool can gradually settle to the bottom of the molten pool through the oxide hard crust.
2022, 51(3):921-926.
DOI: 10.12442/j.issn.1002-185X.20210325
Abstract:
In order to improve the properties of Co-8.8Al-9.8W-2Ta alloy, 0.4at.% Ce and B elements were added to study their effects on the microstructure and properties of the matrix alloy. The results showed that both Ce and B can inhabit the precipitation of the secondary phase, and spheroidize the secondary phase. Co3W phase is precipitated in the grain boundary region of 0.4Ce alloy, Ce mainly formed compounds Ce2Co17 and Al2Ce2Co15. And Co3W and Co7W6 phases are mainly formed in the grain boundary region of 0.4B alloy, and B element mainly formed compound CoW2B2. Both Ce element and B element can improve the microhardness of the alloy, and 0.4Ce alloy owned the highest microhardness.
In order to improve the properties of Co-8.8Al-9.8W-2Ta alloy, 0.4at.% Ce and B elements were added to study their effects on the microstructure and properties of the matrix alloy. The results showed that both Ce and B can inhabit the precipitation of the secondary phase, and spheroidize the secondary phase. Co3W phase is precipitated in the grain boundary region of 0.4Ce alloy, Ce mainly formed compounds Ce2Co17 and Al2Ce2Co15. And Co3W and Co7W6 phases are mainly formed in the grain boundary region of 0.4B alloy, and B element mainly formed compound CoW2B2. Both Ce element and B element can improve the microhardness of the alloy, and 0.4Ce alloy owned the highest microhardness.
2022, 51(3):927-933.
DOI: 10.12442/j.issn.1002-185X.20210225
Abstract:
The vacuum brazing experiment of Si3N4-MoSi2 composite ceramic and Nb was successfully carried out with high-temperature active brazing filler TiZrNiCu. The typical interface structure and formation mechanism of the brazing joint were studied, and the effects of brazing temperature and holding time on interface structure and mechanical properties of brazed joints were analyzed. The results show that the typical interface structure of the joint was Nb/β-Ti/(Ti, Zr)2(Cu, Ni)+β-Ti+(Ti, Zr)5Si3/TiN+(Ti, Zr)5Si3+MoSi2/Si3N4-MoSi2. Brazing temperature and holding time affected the amount and distribution of (Ti, Zr)5si3 compound in the brazing seam by controlling the diffusion degree of Si atoms in Si3N4-MoSi2 composite ceramic to the brazing filler, thus affecting the shear strength of the brazed joint. The highest room temperature shear strength of Nb/Si3N4-MoSi2 joint was 112 MPa at 920 ℃/10 min. The high-temperature shear strength of Nb/Si3N4-MoSi2 brazed joint was 123 MPa and 131 MPa at 500 ℃ and 600 ℃, respectively.
The vacuum brazing experiment of Si3N4-MoSi2 composite ceramic and Nb was successfully carried out with high-temperature active brazing filler TiZrNiCu. The typical interface structure and formation mechanism of the brazing joint were studied, and the effects of brazing temperature and holding time on interface structure and mechanical properties of brazed joints were analyzed. The results show that the typical interface structure of the joint was Nb/β-Ti/(Ti, Zr)2(Cu, Ni)+β-Ti+(Ti, Zr)5Si3/TiN+(Ti, Zr)5Si3+MoSi2/Si3N4-MoSi2. Brazing temperature and holding time affected the amount and distribution of (Ti, Zr)5si3 compound in the brazing seam by controlling the diffusion degree of Si atoms in Si3N4-MoSi2 composite ceramic to the brazing filler, thus affecting the shear strength of the brazed joint. The highest room temperature shear strength of Nb/Si3N4-MoSi2 joint was 112 MPa at 920 ℃/10 min. The high-temperature shear strength of Nb/Si3N4-MoSi2 brazed joint was 123 MPa and 131 MPa at 500 ℃ and 600 ℃, respectively.
2022, 51(3):934-939.
DOI: 10.12442/j.issn.1002-185X.20200367
Abstract:
In this study, the Ti-60Ta alloy bars were prepared by vacuum arc smelting and then forging process. The bulk samples of Ti-60Ta alloy were cut from the bars, some of them were quenched in the water. The spherical powder of Ti-60Ta alloy were prepared by PREP (plasma rotating electrode process). The microstructure and phase transition process were characterized by SEM, XRD, TEM, DSC and so on. It revealed that both of the bulk samples and powders were mainly composed of β-Ti with bcc structure. With the powder size decreasing, the cooling rate was increased during the rapid solidification process, the content of α" martensite phase increased, while the content of β-Ti decreased gradually. The bulk samples were kept at 1000℃ for 60min then quenched in the water, resulting in a small amount of α" martensite phase. The results of TEM and SEAD revealed the lath α" martensite phase with a width of 50 nanometers formed in the powders after rapid solidification, the α" martensite phase mainly precipitated at grain boundaries.
In this study, the Ti-60Ta alloy bars were prepared by vacuum arc smelting and then forging process. The bulk samples of Ti-60Ta alloy were cut from the bars, some of them were quenched in the water. The spherical powder of Ti-60Ta alloy were prepared by PREP (plasma rotating electrode process). The microstructure and phase transition process were characterized by SEM, XRD, TEM, DSC and so on. It revealed that both of the bulk samples and powders were mainly composed of β-Ti with bcc structure. With the powder size decreasing, the cooling rate was increased during the rapid solidification process, the content of α" martensite phase increased, while the content of β-Ti decreased gradually. The bulk samples were kept at 1000℃ for 60min then quenched in the water, resulting in a small amount of α" martensite phase. The results of TEM and SEAD revealed the lath α" martensite phase with a width of 50 nanometers formed in the powders after rapid solidification, the α" martensite phase mainly precipitated at grain boundaries.
2022, 51(3):940-946.
DOI: 10.12442/j.issn.1002-185X.20210237
Abstract:
The linear friction welding behavior of TC17(α+β)/TC17(β) was investigated using several different processing conditions of frequency(20 to 50 Hz), amplitude (1 to 4 mm), friction pressure(32 to 96 MPa). The experimental research analyzed the influence of different welding parameters on the quality of LFWed joints, the microstructure of different regions of joints. The results showed that when the heat input is insufficient, a good welding joint can not be obtained. When other welding parameters remain unchanged, with the increase of single parameter, the heat input increases rapidly, the welding process reached a stable state, and the influence of parameters on the welding process and joint quality was small.?It was observed that phase transition and dynamic recrystallization were occurred in the weld region during the welding process, and finally formed a metastable β phase after weld; the equiaxed and lath α phase were elongated along the vibration direction, and the intergranular needle-like secondary α phase was completely dissolved in both sides of the thermo-mechanically affected zone because of undergoing thermal coupling.
The linear friction welding behavior of TC17(α+β)/TC17(β) was investigated using several different processing conditions of frequency(20 to 50 Hz), amplitude (1 to 4 mm), friction pressure(32 to 96 MPa). The experimental research analyzed the influence of different welding parameters on the quality of LFWed joints, the microstructure of different regions of joints. The results showed that when the heat input is insufficient, a good welding joint can not be obtained. When other welding parameters remain unchanged, with the increase of single parameter, the heat input increases rapidly, the welding process reached a stable state, and the influence of parameters on the welding process and joint quality was small.?It was observed that phase transition and dynamic recrystallization were occurred in the weld region during the welding process, and finally formed a metastable β phase after weld; the equiaxed and lath α phase were elongated along the vibration direction, and the intergranular needle-like secondary α phase was completely dissolved in both sides of the thermo-mechanically affected zone because of undergoing thermal coupling.
2022, 51(3):947-952.
DOI: 10.12442/j.issn.1002-185X.20210250
Abstract:
In this paper, a new high-strength corrosion-resistant titanium alloy is taken as the research object. The effect of annealing process on the microstructure and properties of the plate were studied. After annealing, the overall structure is uniformly distributed. As the annealing temperature increases, the lamellar α phase decreases, the equiaxed α phase increases, and the β-transformed structure grows and increases. When annealed at 740℃, the lamellar α phase basically disappears, the β-transformed structure grew, increased and struck together, showing a typical equiaxed structure. As the annealing temperature increases, the strength and hardness of the plate decrease, the plasticity increases, the corrosion current density decreases, the corrosion rate decreases, and the corrosion resistance increases. After annealing at 740℃ for 1 hour, the plate has the best mechanical properties and corrosion resistance.
In this paper, a new high-strength corrosion-resistant titanium alloy is taken as the research object. The effect of annealing process on the microstructure and properties of the plate were studied. After annealing, the overall structure is uniformly distributed. As the annealing temperature increases, the lamellar α phase decreases, the equiaxed α phase increases, and the β-transformed structure grows and increases. When annealed at 740℃, the lamellar α phase basically disappears, the β-transformed structure grew, increased and struck together, showing a typical equiaxed structure. As the annealing temperature increases, the strength and hardness of the plate decrease, the plasticity increases, the corrosion current density decreases, the corrosion rate decreases, and the corrosion resistance increases. After annealing at 740℃ for 1 hour, the plate has the best mechanical properties and corrosion resistance.
2022, 51(3):953-959.
DOI: 10.12442/j.issn.1002-185X.20210249
Abstract:
In this paper, an alternative alloy of GH4080A for fastener application in the steam turbine running at the parameter near 630℃ was considered. And notch stress rupture tests under different loads processed under the same heat treatments and melted from Special Metals Corporation and Fushun Special Metals Company, respectively. Then, the relationship between characteristics of microstructure near facture zone and the dispersivity of rupture life was systematically investigated by using OM, SEM and EBSD analysis. The results are as follows: the difference of rupture life for specimens melted from Fushun special metals was mainly due to the different grain size distribution at egde and at the center of the billet bar. While the reason that the difference of rupture life for spicimens at the billet bar edge melted from Fushun special metals and Special Metals Corporation was based on the different deformation mechanisms under rupture loads, and grain boundary sliding was the dominant deformation for specimens melted from Fushun, the grain boundary sliding coordinates with intracrystalline plastic deformation for specimens melted form Special Metals Corporation.
In this paper, an alternative alloy of GH4080A for fastener application in the steam turbine running at the parameter near 630℃ was considered. And notch stress rupture tests under different loads processed under the same heat treatments and melted from Special Metals Corporation and Fushun Special Metals Company, respectively. Then, the relationship between characteristics of microstructure near facture zone and the dispersivity of rupture life was systematically investigated by using OM, SEM and EBSD analysis. The results are as follows: the difference of rupture life for specimens melted from Fushun special metals was mainly due to the different grain size distribution at egde and at the center of the billet bar. While the reason that the difference of rupture life for spicimens at the billet bar edge melted from Fushun special metals and Special Metals Corporation was based on the different deformation mechanisms under rupture loads, and grain boundary sliding was the dominant deformation for specimens melted from Fushun, the grain boundary sliding coordinates with intracrystalline plastic deformation for specimens melted form Special Metals Corporation.
2022, 51(3):960-969.
DOI: 10.12442/j.issn.1002-185X.20210244
Abstract:
Metal-organic framework (MOFs)-derived magnetic metal/carbon composites have shown tremendous potential for lightweight microwave absorption materials. Flaky Co/C composites were synthesized by pyrolysis process using two-dimensional flaky Co/Zn bimetallic MOFs as precursors. The effects of Co/Zn molar ratios in the precursor on the morphology structure, graphitization degree, magnetic properties and microwave absorption properties of the composites were investigated. As a result, Co nanoparticles are uniformly distributed in the carbon framework, As the Co content decreases, the graphitization degree of carbon components in composites is decreased, and the magnetic properties are weakened. The microwave absorption properties of flaky Co/C composites are first enhanced and then weakened with the decrease of Co content. The composite with the filling ratio of 30 wt% and Co/Zn molar ratio of 4:1 shows the best microwave absorption properties. The minimum reflection loss (RL) of ?23.09 dB is achieved at 10.8 GHz with the thickness of 2.11 mm. The maximum effective bandwidth (RL≤?10 dB) reaches 4.96 GHz with the thickness of 1.62 mm. The excellent microwave absorption performance of composites mainly due to the synergistic effects of uniformly distributed magnetic Co nanoparticles and carbon frameworks, which enhanced the conduction loss and interfacial polarization and improved the impedance matching.
Metal-organic framework (MOFs)-derived magnetic metal/carbon composites have shown tremendous potential for lightweight microwave absorption materials. Flaky Co/C composites were synthesized by pyrolysis process using two-dimensional flaky Co/Zn bimetallic MOFs as precursors. The effects of Co/Zn molar ratios in the precursor on the morphology structure, graphitization degree, magnetic properties and microwave absorption properties of the composites were investigated. As a result, Co nanoparticles are uniformly distributed in the carbon framework, As the Co content decreases, the graphitization degree of carbon components in composites is decreased, and the magnetic properties are weakened. The microwave absorption properties of flaky Co/C composites are first enhanced and then weakened with the decrease of Co content. The composite with the filling ratio of 30 wt% and Co/Zn molar ratio of 4:1 shows the best microwave absorption properties. The minimum reflection loss (RL) of ?23.09 dB is achieved at 10.8 GHz with the thickness of 2.11 mm. The maximum effective bandwidth (RL≤?10 dB) reaches 4.96 GHz with the thickness of 1.62 mm. The excellent microwave absorption performance of composites mainly due to the synergistic effects of uniformly distributed magnetic Co nanoparticles and carbon frameworks, which enhanced the conduction loss and interfacial polarization and improved the impedance matching.
2022, 51(3):970-976.
DOI: 10.12442/j.issn.1002-185X.20210242
Abstract:
A new way to add Sc in Al alloys using Cu-Sc master alloy was developed. The dissolution behaviors of Cu-Sc master alloy in liquid Al was investigated in this paper. It is was found that the size and areal fraction of particles bearing Sc decrease, the solid solution content of Sc in α Al after solidification increases with increase in holding time and temperature. The grain size of solidified ingots is finer in short holding time. While it increases with increase in holding time and temperature, which is resulted form reduction in the size and areal fraction of particle bearing Sc during dissolution.
A new way to add Sc in Al alloys using Cu-Sc master alloy was developed. The dissolution behaviors of Cu-Sc master alloy in liquid Al was investigated in this paper. It is was found that the size and areal fraction of particles bearing Sc decrease, the solid solution content of Sc in α Al after solidification increases with increase in holding time and temperature. The grain size of solidified ingots is finer in short holding time. While it increases with increase in holding time and temperature, which is resulted form reduction in the size and areal fraction of particle bearing Sc during dissolution.
2022, 51(3):977-982.
DOI: 10.12442/j.issn.1002-185X.20210238
Abstract:
Recently, high entropy ceramics developed by researchers inspired by high entropy alloy have attracted wide attention, due to which can provide new design ideas for the development of non-metallic materials with excellent properties. In this work, based on perovskite ceramic BaMO3, a series of Li-doped high-entropy ceramics Ba(Ti1/7Sn1/7Zr1/7Hf1/7Nb1/7Ga1/7Li(1/7-x))O3 (x = 0, 2.3%, 5.3%, 8.3%, 11.3%) were successfully prepared by solid state reaction. The effects of Li content on the high entropy ceramic phase structure, microstructure and dielectric properties were investigated. The results show that the grain sizes of these ceramics are uniform, and the effect of Li content on the structure of ceramics is not significant. All ceramics are of cubic perovskite structure without obvious impurity phase. When x = 0, the ceramic is represented as seven-component equimolar high entropy ceramic Ba(Ti1/7Sn1/7Zr1/7Hf1/7Nb1/7Ga1/7Li1/7)O3, which exhibits excellent dielectric properties, with dielectric constant reached the maximum value of 2920 (@ 100 Hz), nearly 50 times as much as the value of Li-undoped six-component equimolar high entropy ceramic Ba (Ti1/6Sn1/6 Zr1/6 Hf1/6 Nb1/6 Ga1/6) O3.
Recently, high entropy ceramics developed by researchers inspired by high entropy alloy have attracted wide attention, due to which can provide new design ideas for the development of non-metallic materials with excellent properties. In this work, based on perovskite ceramic BaMO3, a series of Li-doped high-entropy ceramics Ba(Ti1/7Sn1/7Zr1/7Hf1/7Nb1/7Ga1/7Li(1/7-x))O3 (x = 0, 2.3%, 5.3%, 8.3%, 11.3%) were successfully prepared by solid state reaction. The effects of Li content on the high entropy ceramic phase structure, microstructure and dielectric properties were investigated. The results show that the grain sizes of these ceramics are uniform, and the effect of Li content on the structure of ceramics is not significant. All ceramics are of cubic perovskite structure without obvious impurity phase. When x = 0, the ceramic is represented as seven-component equimolar high entropy ceramic Ba(Ti1/7Sn1/7Zr1/7Hf1/7Nb1/7Ga1/7Li1/7)O3, which exhibits excellent dielectric properties, with dielectric constant reached the maximum value of 2920 (@ 100 Hz), nearly 50 times as much as the value of Li-undoped six-component equimolar high entropy ceramic Ba (Ti1/6Sn1/6 Zr1/6 Hf1/6 Nb1/6 Ga1/6) O3.
2022, 51(3):983-989.
DOI: 10.12442/j.issn.1002-185X.20210252
Abstract:
In order to ensure the safety and operation of long-term orbiting spacecraft, and to improve the protection performance of the shielding configuration in response to the hypervelocity impact of small space debris, it is necessary to optimize and improve the bumper materials. In this paper, the SiC/Al composite bumper material is prepared by pressure infiltration in the SiC porous ceramic pre-sintered body, and the space debris hypervelocity impact experiment of the SiC/Al bumper configuration is carried out on a two-stage light-gas gun. The impact damage behavior of the SiC/Al bumper material, the structural characteristics of the secondary debris cloud, and the impact damage feature of the rear wall are investigated in this paper. The research results show that the SiC/Al bumper could broken the space debris into smaller debris than traditional Al-alloy bumper did, and the expanded secondary debris cloud structure was formed behind the SiC/Al bumper. Based on the SEM damage morphology analysis of the impact craters on the rear wall, with the increase of the impact velocity of space debris, a more significant impact phenomenon of secondary debris in the liquid phase occurred, and the protection performance of shielding configuration was enhanced accordingly.
In order to ensure the safety and operation of long-term orbiting spacecraft, and to improve the protection performance of the shielding configuration in response to the hypervelocity impact of small space debris, it is necessary to optimize and improve the bumper materials. In this paper, the SiC/Al composite bumper material is prepared by pressure infiltration in the SiC porous ceramic pre-sintered body, and the space debris hypervelocity impact experiment of the SiC/Al bumper configuration is carried out on a two-stage light-gas gun. The impact damage behavior of the SiC/Al bumper material, the structural characteristics of the secondary debris cloud, and the impact damage feature of the rear wall are investigated in this paper. The research results show that the SiC/Al bumper could broken the space debris into smaller debris than traditional Al-alloy bumper did, and the expanded secondary debris cloud structure was formed behind the SiC/Al bumper. Based on the SEM damage morphology analysis of the impact craters on the rear wall, with the increase of the impact velocity of space debris, a more significant impact phenomenon of secondary debris in the liquid phase occurred, and the protection performance of shielding configuration was enhanced accordingly.
2022, 51(3):990-996.
DOI: 10.12442/j.issn.1002-185X.20210254
Abstract:
Aluminum alloy materials have the advantages of low density, high specific strength, good corrosion resistance, etc., which are currently a hot spot especially in industrial research. In this paper, an Al-7.51Zn-2.37Mg-1.72Cu drill pipe material suitable for the oil and gas industry is designed for the 7xxx series aluminum alloy. The effect of aging treatment on the mechanical properties and thermal stability of aluminum alloy drill pipe materials was studied through age hardening behavior, mechanical performance evaluation and microstructure characterization. The results show that the optimal aging time of Al-7.51Zn-2.37Mg-1.72Cu is 24h when the aging temperature is 120℃. The tensile strength, yield strength and elongation (Rm, R0.2 and A) of the quenched state changes from 693MPa, 566MPa and 15% to 720MPa, 692MPa and 14%, respectively. After 500 hours of heat exposure at 200℃, Rm and R0.2 are reduced by 55.6% and 67.3% compared with the aging state, and the elongation is increased by 15.8% on average. This is mainly because the GP zone in the alloy matrix and some of the small and poorly stable η" phases begin to re-dissolve, and the larger and more stable η phase will transform into η" phase. At the same time, the existing η phases in the matrix converge into large mass points.
Aluminum alloy materials have the advantages of low density, high specific strength, good corrosion resistance, etc., which are currently a hot spot especially in industrial research. In this paper, an Al-7.51Zn-2.37Mg-1.72Cu drill pipe material suitable for the oil and gas industry is designed for the 7xxx series aluminum alloy. The effect of aging treatment on the mechanical properties and thermal stability of aluminum alloy drill pipe materials was studied through age hardening behavior, mechanical performance evaluation and microstructure characterization. The results show that the optimal aging time of Al-7.51Zn-2.37Mg-1.72Cu is 24h when the aging temperature is 120℃. The tensile strength, yield strength and elongation (Rm, R0.2 and A) of the quenched state changes from 693MPa, 566MPa and 15% to 720MPa, 692MPa and 14%, respectively. After 500 hours of heat exposure at 200℃, Rm and R0.2 are reduced by 55.6% and 67.3% compared with the aging state, and the elongation is increased by 15.8% on average. This is mainly because the GP zone in the alloy matrix and some of the small and poorly stable η" phases begin to re-dissolve, and the larger and more stable η phase will transform into η" phase. At the same time, the existing η phases in the matrix converge into large mass points.
33 Rapid sintering and high temperature oxidation behavior of MoSi2-B4C composite coatings on Nb alloy
2022, 51(3):997-1002.
DOI: 10.12442/j.issn.1002-185X.20210258
Abstract:
MoSi2-B4C composite coatings were prepared on Nb alloy by spark plasma sintering process. Pure Mo, Si and B4C powders were used as the coating starting materials. The microstructure formation process and interface reaction characteristics of the coatings during SPS were studied. The oxidation resistance of the coatings at 1450℃ was investigated. The results showed that the MoSi2 phase formed completely in the coatings during the heating stage of sintering, and the B4C particles reacted with the neighboring MoSi2 to form SiC and Mo2B5 at the initial stage of holding time. During the sintering process, elements Si and B diffused inwardly from the coatings to the Nb substrate, forming an interdiffusion zone composed of NbSi2+ NbB outer layer and Nb5Si3 inner layer. The coatings could protect Nb alloy effectively from oxidation at 1450℃ for at least 100h, and dense SiO2-B2O3 oxide scales were formed on the surfaces of the coatings. The presence of NbB in the interdiffusion zone effectively impeded the inward diffusion of Si in the coating during the oxidation process.
MoSi2-B4C composite coatings were prepared on Nb alloy by spark plasma sintering process. Pure Mo, Si and B4C powders were used as the coating starting materials. The microstructure formation process and interface reaction characteristics of the coatings during SPS were studied. The oxidation resistance of the coatings at 1450℃ was investigated. The results showed that the MoSi2 phase formed completely in the coatings during the heating stage of sintering, and the B4C particles reacted with the neighboring MoSi2 to form SiC and Mo2B5 at the initial stage of holding time. During the sintering process, elements Si and B diffused inwardly from the coatings to the Nb substrate, forming an interdiffusion zone composed of NbSi2+ NbB outer layer and Nb5Si3 inner layer. The coatings could protect Nb alloy effectively from oxidation at 1450℃ for at least 100h, and dense SiO2-B2O3 oxide scales were formed on the surfaces of the coatings. The presence of NbB in the interdiffusion zone effectively impeded the inward diffusion of Si in the coating during the oxidation process.
2022, 51(3):1003-1010.
DOI: 10.12442/j.issn.1002-185X.20210220
Abstract:
La1-xSrxMnO3 nanometer powders were prepared by sol-gel method. The crystal structure, magnetic properties, electromagnetic properties and microwave absorption properties of LSMO with different doping amount of Sr2+ were investigated. The results show that with increased amount of Sr2+, the lattice constant and Mn-O-Mn bond Angle increase, while the average grain size decreases gradually and the complex dielectric constant increases first and then decreases. The LSMO changes from antiferromagnetism to ferromagnetism when Sr2+ is doped. In the range of 2~18GHz, the best absorbing properties can be arrived when the doping amount of Sr2+ is 0 and the thickness is 2mm. The effective frequency band corresponding to the reflectivity less than -10dB is 12.5~18GHz. The doping of Sr2+ can make the absorbing bandwidth move to the low frequency availably. In the X-band, the effective bandwidth of the LSMO reaches 2.6GHz when the doping amount of Sr2+ is 0.2 and the thickness is 2.3mm. It is proved that LSMO is a kind of dielectric loss absorbing material with excellent performance.
La1-xSrxMnO3 nanometer powders were prepared by sol-gel method. The crystal structure, magnetic properties, electromagnetic properties and microwave absorption properties of LSMO with different doping amount of Sr2+ were investigated. The results show that with increased amount of Sr2+, the lattice constant and Mn-O-Mn bond Angle increase, while the average grain size decreases gradually and the complex dielectric constant increases first and then decreases. The LSMO changes from antiferromagnetism to ferromagnetism when Sr2+ is doped. In the range of 2~18GHz, the best absorbing properties can be arrived when the doping amount of Sr2+ is 0 and the thickness is 2mm. The effective frequency band corresponding to the reflectivity less than -10dB is 12.5~18GHz. The doping of Sr2+ can make the absorbing bandwidth move to the low frequency availably. In the X-band, the effective bandwidth of the LSMO reaches 2.6GHz when the doping amount of Sr2+ is 0.2 and the thickness is 2.3mm. It is proved that LSMO is a kind of dielectric loss absorbing material with excellent performance.
2022, 51(3):1011-1016.
DOI: 10.12442/j.issn.1002-185X.20210203
Abstract:
In this study, a series of TC4 alloy single tracks were prepared by electron beam melting, the process parameters such as scanning speed, beam current, and focus offset were adjusted to investigate the influence of process parameters on the surface morphology and geometrical characteristics (re-melt depth, track width, track height, contact angle and aspect ratio) of a single track. The results showed that the linear energy input increased with the decrease of scanning speed and the increase of beam current, the width and continuity of single tracks were improved. When other parameters were fixed, with the increase of scanning speed, the single track became discontinuous and even the balling effect could be observed. The scanning speed, beam current, and focus offset all have a great influence on the melt pool, with the decrease of scanning speed and the increase of beam current, the re-melt depth, track width, and track height increased. When the focus offset was 3mA, the re-melt depth and track width were maximum while the contact angle was the minimum. For the constant of beam current, with the increase of scanning speed, the contact angle increased first and then decreased while the aspect ratio decreased.
In this study, a series of TC4 alloy single tracks were prepared by electron beam melting, the process parameters such as scanning speed, beam current, and focus offset were adjusted to investigate the influence of process parameters on the surface morphology and geometrical characteristics (re-melt depth, track width, track height, contact angle and aspect ratio) of a single track. The results showed that the linear energy input increased with the decrease of scanning speed and the increase of beam current, the width and continuity of single tracks were improved. When other parameters were fixed, with the increase of scanning speed, the single track became discontinuous and even the balling effect could be observed. The scanning speed, beam current, and focus offset all have a great influence on the melt pool, with the decrease of scanning speed and the increase of beam current, the re-melt depth, track width, and track height increased. When the focus offset was 3mA, the re-melt depth and track width were maximum while the contact angle was the minimum. For the constant of beam current, with the increase of scanning speed, the contact angle increased first and then decreased while the aspect ratio decreased.
2022, 51(3):1017-1023.
DOI: 10.12442/j.issn.1002-185X.20210212
Abstract:
The BP and GO were dispersed by liquid-phase stripping technique. By covalent bonding, BP-GO composite carrier was prepared. AgNPs were reduced in situ on the surface of BP-GO composite carrier by redox method.The effects of silver nitrate content and BP-GO content ratio on the properties of composite powders were investigated, and the antibacterial properties of BP-GO-AgNPs and GO-AgNPs composite coatings prepared under the same conditions were compared and analyzed.SEM and TEM analysis showed that BP and GO were successfully dispersed, BP-GO carrier was successfully combined, and AgNPs were successfully loaded on the carrier surface,with the optimal AgNO3 dosage parameter was 3×10-4mol.XPS analysis showed that BP-GO-AgNPs composite powders were successfully prepared by the joint of P-C and P-O-C, and the AgNPs were successfully loaded on the surface of the carrier.Raman analysis showed that the optimal ratio of BP-GO content in the composite powder was 1:1.The antibacterial results showed that the BP-GO-AgNPs composite coating had better antibacterial effect than the GO-AgNPs composite coating under the same conditions.
The BP and GO were dispersed by liquid-phase stripping technique. By covalent bonding, BP-GO composite carrier was prepared. AgNPs were reduced in situ on the surface of BP-GO composite carrier by redox method.The effects of silver nitrate content and BP-GO content ratio on the properties of composite powders were investigated, and the antibacterial properties of BP-GO-AgNPs and GO-AgNPs composite coatings prepared under the same conditions were compared and analyzed.SEM and TEM analysis showed that BP and GO were successfully dispersed, BP-GO carrier was successfully combined, and AgNPs were successfully loaded on the carrier surface,with the optimal AgNO3 dosage parameter was 3×10-4mol.XPS analysis showed that BP-GO-AgNPs composite powders were successfully prepared by the joint of P-C and P-O-C, and the AgNPs were successfully loaded on the surface of the carrier.Raman analysis showed that the optimal ratio of BP-GO content in the composite powder was 1:1.The antibacterial results showed that the BP-GO-AgNPs composite coating had better antibacterial effect than the GO-AgNPs composite coating under the same conditions.
2022, 51(3):1024-1030.
DOI: 10.12442/j.issn.1002-185X.20210198
Abstract:
Five refractory high-entropy alloys with nominal composition of NbMo0.5HfxTiZrCrAl (x=0, 0.25, 0.5, 0.75, 1, at.%) were prepared by vacuum non-consumable arc smelting. The effects of Hf addition on the microstructure and mechanical properties of the alloys were studied. The results show that the microstructures of the alloys with and without Hf are composed of two BCC phases (namely BCC1 and BCC2) and Laves phase. In the alloy without adding Hf, the BCC1 phase is mainly rich in Zr, Cr and Al elements, and the BCC2 phase is mainly rich in Nb, Ti and Mo elements. In the Hf-added alloys, the BCC1 phase is mainly rich in Hf, Zr, Cr, Mo and Al elements, and the BCC2 phase is mainly rich in Nb and Ti elements. With the increase of Hf content, the amount of BCC1 phase gradually increases, and the lattice constants of BCC1 and BCC2 phases both increase. In addition, with the increase of Hf content, the microhardness and brittleness of the alloy gradually increase, and the compressive strength of the alloy at 1200 ℃ gradually decreases.
Five refractory high-entropy alloys with nominal composition of NbMo0.5HfxTiZrCrAl (x=0, 0.25, 0.5, 0.75, 1, at.%) were prepared by vacuum non-consumable arc smelting. The effects of Hf addition on the microstructure and mechanical properties of the alloys were studied. The results show that the microstructures of the alloys with and without Hf are composed of two BCC phases (namely BCC1 and BCC2) and Laves phase. In the alloy without adding Hf, the BCC1 phase is mainly rich in Zr, Cr and Al elements, and the BCC2 phase is mainly rich in Nb, Ti and Mo elements. In the Hf-added alloys, the BCC1 phase is mainly rich in Hf, Zr, Cr, Mo and Al elements, and the BCC2 phase is mainly rich in Nb and Ti elements. With the increase of Hf content, the amount of BCC1 phase gradually increases, and the lattice constants of BCC1 and BCC2 phases both increase. In addition, with the increase of Hf content, the microhardness and brittleness of the alloy gradually increase, and the compressive strength of the alloy at 1200 ℃ gradually decreases.
2022, 51(3):1031-1039.
DOI: 10.12442/j.issn.1002-185X.20210156
Abstract:
In order to study the microstructure, tensile properties, strain-controlled low cycle fatigue properties and fracture morphology of a novel nickel-based powder metallurgy(P/M) superalloy (WZ-A3) under different conditionss, the scanning electron microscopy, optical metalloscopy, fatigue testing machine and tensile testing machine were used.The results show that the Previous Particle Boundary (PPB) formed during the Hot Isostatic Pressing (HIP) process were fully eliminated by Hot Extrusion (HEX). With the increase of tensile temperature from room temperature to 800℃, the tensile strength of the alloy decreases first (from room temperature to 400℃), remains unchanged (from 400℃ to 550℃), and then decreases (from 550℃ to 800℃). At room temperature, The Elongation of the HIP+HT samples were reduced by PPB. From 700℃ to 800℃, these two states of the tensile fracture changed from the mixed transgranular and intergranular fracture mode to the intergranular fracture mode. The fatigue life (Nf) of HIP+HEX+HT samples was higher than that of HIP +HT samples under small strain control (0.6%, 0.8%), which was related to inclusions in the alloy. When the strain was large (1.0%, 1.2%, 1.4%), the Nf were close to each other. When the strain was 1.2%, the multiple platform-type fatigue crack sources appeared in both samples.
In order to study the microstructure, tensile properties, strain-controlled low cycle fatigue properties and fracture morphology of a novel nickel-based powder metallurgy(P/M) superalloy (WZ-A3) under different conditionss, the scanning electron microscopy, optical metalloscopy, fatigue testing machine and tensile testing machine were used.The results show that the Previous Particle Boundary (PPB) formed during the Hot Isostatic Pressing (HIP) process were fully eliminated by Hot Extrusion (HEX). With the increase of tensile temperature from room temperature to 800℃, the tensile strength of the alloy decreases first (from room temperature to 400℃), remains unchanged (from 400℃ to 550℃), and then decreases (from 550℃ to 800℃). At room temperature, The Elongation of the HIP+HT samples were reduced by PPB. From 700℃ to 800℃, these two states of the tensile fracture changed from the mixed transgranular and intergranular fracture mode to the intergranular fracture mode. The fatigue life (Nf) of HIP+HEX+HT samples was higher than that of HIP +HT samples under small strain control (0.6%, 0.8%), which was related to inclusions in the alloy. When the strain was large (1.0%, 1.2%, 1.4%), the Nf were close to each other. When the strain was 1.2%, the multiple platform-type fatigue crack sources appeared in both samples.
2022, 51(3):1040-1046.
DOI: 10.12442/j.issn.1002-185X.20210138
Abstract:
Amorphous alloy is a new type of multicomponent alloy material which is different from common metal materials, in which rare earth-based amorphous alloy is an important member of metallic glass family. However, due to the high activity of rare earth elements and stringent preparation requirements of metallic glass, the related research progress is slow, and the research of new system amorphous alloy still adopts a large number of original methods of trial and error. In this paper, based on the concept of high-throughput material genetic engineering, metal thin films with continuous change of chemical composition were prepared by tilting target and adjusting single metal target power, so as to quickly screen the composition range of YbCu amorphous alloy, and successfully prepared YbCu amorphous alloy film for the first time. At the same time, the influence of aluminum on the formation of YbCu amorphous alloy was studied and prepared YbCuAl amorphous films were prepared. When the Yb is less than 44.5-46.5 wt%, the films are all amorphous. The results show that the surface of YbCu amorphous alloy is smooth without defects, and the absolute height difference is only 31.6 nm. The film is hydrophobic with a maximum hydrophobic angle of 119 °. In addition, the maximum square resistance of YbCu and YbCuAl amorphous films is 551 mΩ □-1 and 1738 mΩ □-1, respectively. The alloying element Al has a significant effect on the properties of YbCu amorphous films. Therefore, the composition screening and successful preparation of YbCu(Al) amorphous films accelerate the development of rare earth based amorphous materials.
Amorphous alloy is a new type of multicomponent alloy material which is different from common metal materials, in which rare earth-based amorphous alloy is an important member of metallic glass family. However, due to the high activity of rare earth elements and stringent preparation requirements of metallic glass, the related research progress is slow, and the research of new system amorphous alloy still adopts a large number of original methods of trial and error. In this paper, based on the concept of high-throughput material genetic engineering, metal thin films with continuous change of chemical composition were prepared by tilting target and adjusting single metal target power, so as to quickly screen the composition range of YbCu amorphous alloy, and successfully prepared YbCu amorphous alloy film for the first time. At the same time, the influence of aluminum on the formation of YbCu amorphous alloy was studied and prepared YbCuAl amorphous films were prepared. When the Yb is less than 44.5-46.5 wt%, the films are all amorphous. The results show that the surface of YbCu amorphous alloy is smooth without defects, and the absolute height difference is only 31.6 nm. The film is hydrophobic with a maximum hydrophobic angle of 119 °. In addition, the maximum square resistance of YbCu and YbCuAl amorphous films is 551 mΩ □-1 and 1738 mΩ □-1, respectively. The alloying element Al has a significant effect on the properties of YbCu amorphous films. Therefore, the composition screening and successful preparation of YbCu(Al) amorphous films accelerate the development of rare earth based amorphous materials.
2022, 51(3):1047-1054.
DOI: 10.12442/j.issn.1002-185X.20210899
Abstract:
Abstract: The friction stir welding (FSW) process tests of three-layer composite plate Al/AZ31/Al at different welding speeds were carried out, and the joint forming, microstructure and tensile properties were observed and analyzed. The results show that under the optimized process parameters, the welded joint is well formed, and its internal distribution is layered, and no defects are found. The grain refinement in nugget zone (NZ) is obvious, and the large angle grain boundaries (HAGBs) and recrystallized grains account for 80%. There is intermetallic compound (IMC) in the banded structure area (BS) on the forward side of the weld and the interface between magnesium and aluminum, which is mainly composed of Al3Mg2 and Al12Mg17. With the increase of welding speed, the tensile strength of welded joint first increases and then decreases. When v=100 mm/min, the average grain size of the aluminum layer in the weld nugget area is 1.75 μm, and the tensile strength of the welded joint reaches the maximum 87.3 MPa, which is 50.8% of the base metal.
Abstract: The friction stir welding (FSW) process tests of three-layer composite plate Al/AZ31/Al at different welding speeds were carried out, and the joint forming, microstructure and tensile properties were observed and analyzed. The results show that under the optimized process parameters, the welded joint is well formed, and its internal distribution is layered, and no defects are found. The grain refinement in nugget zone (NZ) is obvious, and the large angle grain boundaries (HAGBs) and recrystallized grains account for 80%. There is intermetallic compound (IMC) in the banded structure area (BS) on the forward side of the weld and the interface between magnesium and aluminum, which is mainly composed of Al3Mg2 and Al12Mg17. With the increase of welding speed, the tensile strength of welded joint first increases and then decreases. When v=100 mm/min, the average grain size of the aluminum layer in the weld nugget area is 1.75 μm, and the tensile strength of the welded joint reaches the maximum 87.3 MPa, which is 50.8% of the base metal.
2022, 51(3):1055-1062.
DOI: 10.12442/j.issn.1002-185X.20200708
Abstract:
In the present work, Ti fiber with a diameter of 200μm was used as the reaction source, and pure aluminum with a purity of 99.6wt.% was used as the matrix. The reaction source was fixed in the matrix at equal intervals during the preparation of the preform to pre-control the initial position of the product. Subsequently, the preform was placed in the induction heating furnace, and at the same time, the constant gradient alternating current were applied to promote the in-situ reaction between Al-Ti, in order to obtain Al3Ti particle-reinforced aluminum matrix composite material. The phase composition, microstructure and wear resistance of the composite material under different currents were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM) and wear testers. The results show that when the current is 15A, the Ti fiber is completely reacted, and the product is the isometric Al3Ti with a size of 1-2μm and a particle spacing of about 5μm, reaching the optimal value under all parameters. Under the condition of a load of 10N, the wear resistance of the composite is the best at 15A, and the friction coefficient and wear amount are the lowest values of 0.1 and 2.031mg/mm2 respectively.
In the present work, Ti fiber with a diameter of 200μm was used as the reaction source, and pure aluminum with a purity of 99.6wt.% was used as the matrix. The reaction source was fixed in the matrix at equal intervals during the preparation of the preform to pre-control the initial position of the product. Subsequently, the preform was placed in the induction heating furnace, and at the same time, the constant gradient alternating current were applied to promote the in-situ reaction between Al-Ti, in order to obtain Al3Ti particle-reinforced aluminum matrix composite material. The phase composition, microstructure and wear resistance of the composite material under different currents were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM) and wear testers. The results show that when the current is 15A, the Ti fiber is completely reacted, and the product is the isometric Al3Ti with a size of 1-2μm and a particle spacing of about 5μm, reaching the optimal value under all parameters. Under the condition of a load of 10N, the wear resistance of the composite is the best at 15A, and the friction coefficient and wear amount are the lowest values of 0.1 and 2.031mg/mm2 respectively.
Fangzhe Li
,
Hua Ke
,
Hongjun Zhang
,
Miao Xing
,
Jingxin Tian
,
Xiaohui Tang
,
Dechang Jia
,
Yu Zhou
2022, 51(3):1063-1071.
DOI: 10.12442/j.issn.1002-185X.20210262
Abstract:
The 0-3 type Na0.5Bi0.5TiO3-CoFe2O4 (NBT-CFO) composite multiferroic ceramics with embedded structures were prepared by an in-situ sol-gel method, and its electrical and magnetic properties were studied. The crystallization behavior was studied by TG-DTA and XRD. Based on the difference between the crystallization temperatures of CFO and NBT, a two-step calcination process was designed to obtain NBT-CFO nano-powders with the average size of 45 nm. 0.9NBT-0.1CFO composite ceramics sintered using the nano-powders had embedded structures, where the CFO grains are uniformly distributed inside the NBT grains. Compared to the composite ceramics prepared by the mechanical mixing method, the 0.9NBT-0.1CFO composite ceramics with embedded structures have lower dielectric loss in 250-1M Hz at room temperature, and the loss at 250 Hz is only 30% of the former. The temperature dependent relative permittivities, impedance spectrum and mode spectrum show that composite ceramics with embedded structures exhibit dielectric relaxation behavior caused by the interfacial polarization between NBT and CFO at 350-650 oC, and the activation energy is 0.77 eV. 0.9NBT-0.1CFO composite ceramics with embedded structures have the larger remanent polarization, higher breakdown strength and greater ferroelectric performances at room temperature.
The 0-3 type Na0.5Bi0.5TiO3-CoFe2O4 (NBT-CFO) composite multiferroic ceramics with embedded structures were prepared by an in-situ sol-gel method, and its electrical and magnetic properties were studied. The crystallization behavior was studied by TG-DTA and XRD. Based on the difference between the crystallization temperatures of CFO and NBT, a two-step calcination process was designed to obtain NBT-CFO nano-powders with the average size of 45 nm. 0.9NBT-0.1CFO composite ceramics sintered using the nano-powders had embedded structures, where the CFO grains are uniformly distributed inside the NBT grains. Compared to the composite ceramics prepared by the mechanical mixing method, the 0.9NBT-0.1CFO composite ceramics with embedded structures have lower dielectric loss in 250-1M Hz at room temperature, and the loss at 250 Hz is only 30% of the former. The temperature dependent relative permittivities, impedance spectrum and mode spectrum show that composite ceramics with embedded structures exhibit dielectric relaxation behavior caused by the interfacial polarization between NBT and CFO at 350-650 oC, and the activation energy is 0.77 eV. 0.9NBT-0.1CFO composite ceramics with embedded structures have the larger remanent polarization, higher breakdown strength and greater ferroelectric performances at room temperature.
2022, 51(3):1072-1080.
DOI: 10.12442/j.issn.1002-185X.20210247
Abstract:
The particle-stabilized foams method was successfully applied to fabricate the lightweight YSZ ceramic foams with closed pore structure and uniform pore size distribution. The microstructure of YSZ ceramic foams, including strut structure, porosity, mean pore size and pore size distribution were tailored by varying the sintering temperature, surfactant type and solid content of the initial slurries. When the sintering temperature at 1450 ℃ and solid content 32.50 vol%, YSZ ceramic foams with porosity of 83.7±0.2 %, mean pore size of 90.1±0.8 μm and compressive strength of 45.1±1.3 MPa were obtained through Isobam molecule and cationic surfactant dodecyl trimethyl ammonium chloride (DTAC) co-stabilized YSZ wet foam. The compressive strength of YSZ ceramic foams in present work was much higher than most reported results in the case of same porosity.
The particle-stabilized foams method was successfully applied to fabricate the lightweight YSZ ceramic foams with closed pore structure and uniform pore size distribution. The microstructure of YSZ ceramic foams, including strut structure, porosity, mean pore size and pore size distribution were tailored by varying the sintering temperature, surfactant type and solid content of the initial slurries. When the sintering temperature at 1450 ℃ and solid content 32.50 vol%, YSZ ceramic foams with porosity of 83.7±0.2 %, mean pore size of 90.1±0.8 μm and compressive strength of 45.1±1.3 MPa were obtained through Isobam molecule and cationic surfactant dodecyl trimethyl ammonium chloride (DTAC) co-stabilized YSZ wet foam. The compressive strength of YSZ ceramic foams in present work was much higher than most reported results in the case of same porosity.
Zhao Zhao
,
Liang Doudou
,
Wu Yin
,
Zhang Rui
,
Shi Jianlei
,
Zhao Yinghao
,
Shan Zhihang
,
Zhou Wei
,
Zhang Boping
2022, 51(3):1081-1086.
DOI: 10.12442/j.issn.1002-185X.20210236
Abstract:
Digenite (Cu1.8S) as a potential p-type thermoelectric (TE) material has attracted extensive attention due to its environmental benign, abundant resources and low cost of component elements. In this study, the TE properties of Cu1.8S-x wt%BaTiO3 bulk samples prepared by mechanical alloying (MA) combined with spark plasma sintering (SPS) were investigated. Adding BaTiO3 would refine grains, thereby increasing the phonons scattering and reducing the thermal conductivity k. The k for Cu1.8S-0.2 wt%BaTiO3 is 2.2 W m-1 K-1 which is 18% lower than that for pristine Cu1.8S (2.69 W m-1 K-1). The refined grains also enhance the carriers scattering, and reduce the carrier mobility to reduce the power factor (PF). Combine with the decreased PF and k, the calculated ZT values are barely unchanged for adding BaTiO3 in Cu1.8S. The Vickers-hardness for BaTiO3-adding samples are improved due to the refined grains and the pinning effect of BaTiO3 on grain boundary. This study shows that the mechanical properties of Cu1.8S bulk samples can be effectively improved by compositing nano BaTiO3 with little affecting TE properties, which provides ideas for preparing high mechanical properties and durable TE devices of Cu-S system.
Digenite (Cu1.8S) as a potential p-type thermoelectric (TE) material has attracted extensive attention due to its environmental benign, abundant resources and low cost of component elements. In this study, the TE properties of Cu1.8S-x wt%BaTiO3 bulk samples prepared by mechanical alloying (MA) combined with spark plasma sintering (SPS) were investigated. Adding BaTiO3 would refine grains, thereby increasing the phonons scattering and reducing the thermal conductivity k. The k for Cu1.8S-0.2 wt%BaTiO3 is 2.2 W m-1 K-1 which is 18% lower than that for pristine Cu1.8S (2.69 W m-1 K-1). The refined grains also enhance the carriers scattering, and reduce the carrier mobility to reduce the power factor (PF). Combine with the decreased PF and k, the calculated ZT values are barely unchanged for adding BaTiO3 in Cu1.8S. The Vickers-hardness for BaTiO3-adding samples are improved due to the refined grains and the pinning effect of BaTiO3 on grain boundary. This study shows that the mechanical properties of Cu1.8S bulk samples can be effectively improved by compositing nano BaTiO3 with little affecting TE properties, which provides ideas for preparing high mechanical properties and durable TE devices of Cu-S system.
2022, 51(3):1087-1099.
DOI: 10.12442/j.issn.1002-185X.20210141
Abstract:
Titanium diboride (TiB2), as the compound with the smallest density and the highest hardness among metal borides, is one of the important advanced ceramic materials. It not only has the high melting point, high hardness and good chemical stability of traditional ceramics, but also has excellent electrical conductivity that traditional ceramics do not have. These properties render it suitable for many applications, such as in the manufacture of wear resistant parts and metal evaporation boats. Such excellent properties also make it a promising candidate as a coating material on cutting tools, cathodes in Hall-Heroult cells for primary aluminum smelting and aerospace vehicle parts. Based on the current research status, this article focuses on the advantages and disadvantages of the TiB2 coating preparation technology such as vapor deposition, electrochemical deposition, thermal spraying, surface cladding, electric spark deposition and Sol-Gel. Moreover, the important applications of TiB2 ceramic coating in key fields are summarized, and the future development direction is prospected.
Titanium diboride (TiB2), as the compound with the smallest density and the highest hardness among metal borides, is one of the important advanced ceramic materials. It not only has the high melting point, high hardness and good chemical stability of traditional ceramics, but also has excellent electrical conductivity that traditional ceramics do not have. These properties render it suitable for many applications, such as in the manufacture of wear resistant parts and metal evaporation boats. Such excellent properties also make it a promising candidate as a coating material on cutting tools, cathodes in Hall-Heroult cells for primary aluminum smelting and aerospace vehicle parts. Based on the current research status, this article focuses on the advantages and disadvantages of the TiB2 coating preparation technology such as vapor deposition, electrochemical deposition, thermal spraying, surface cladding, electric spark deposition and Sol-Gel. Moreover, the important applications of TiB2 ceramic coating in key fields are summarized, and the future development direction is prospected.
2022, 51(3):1100-1110.
DOI: 10.12442/j.issn.1002-185X.20210160
Abstract:
Tungsten has been considered as one of the most promising candidates for plasma-facing materials in next-step fusion energy systems. The helium and hydrogen bubbles lead to the serious damage of structure and degeneration of thermal and mechanical properties of W. It is still difficult to reveal the physical mechanisms of interaction between radiation defects and helium/hydrogen by using experimental skills, however, the multi-scale computation and simulation are more effective. Based on the progress of different computation and simulation methods in recent years, this paper systematically introduces the effect of the defect type, concentrations, size, distribution and temperature. Meanwhile, the binding energy, formation energy, diffusion path, diffusion barrier, clustering bhaviors and microstructure evolution are discussed. In the end, the existing key scientific problems and development trend are pointed. The results are contributing directly to the design, preparation and application of W based materials under a fusion environment.
Tungsten has been considered as one of the most promising candidates for plasma-facing materials in next-step fusion energy systems. The helium and hydrogen bubbles lead to the serious damage of structure and degeneration of thermal and mechanical properties of W. It is still difficult to reveal the physical mechanisms of interaction between radiation defects and helium/hydrogen by using experimental skills, however, the multi-scale computation and simulation are more effective. Based on the progress of different computation and simulation methods in recent years, this paper systematically introduces the effect of the defect type, concentrations, size, distribution and temperature. Meanwhile, the binding energy, formation energy, diffusion path, diffusion barrier, clustering bhaviors and microstructure evolution are discussed. In the end, the existing key scientific problems and development trend are pointed. The results are contributing directly to the design, preparation and application of W based materials under a fusion environment.
2022, 51(3):1111-1124.
DOI: 10.12442/j.issn.1002-185X.20210184
Abstract:
Titanium and its alloys have been widely used in biomedical field due to their excellent biocompatibility, low elastic modulus, good comprehensive mechanical properties and corrosion resistance. It was one of the most promising medical metal materials than stainless steel and cobalt chromium alloys. From the perspective of biomechanical properties, biological corrosion resistance, biocompatibility and antibacterial properties, the development status of metastable β-titanium alloys and its research process are summarized. Especially, the research status of improving the mechanical properties of β-titanium alloys by altering the alloy elements, changing heat treatment process and alloy forming methods are well focused on.
Titanium and its alloys have been widely used in biomedical field due to their excellent biocompatibility, low elastic modulus, good comprehensive mechanical properties and corrosion resistance. It was one of the most promising medical metal materials than stainless steel and cobalt chromium alloys. From the perspective of biomechanical properties, biological corrosion resistance, biocompatibility and antibacterial properties, the development status of metastable β-titanium alloys and its research process are summarized. Especially, the research status of improving the mechanical properties of β-titanium alloys by altering the alloy elements, changing heat treatment process and alloy forming methods are well focused on.
2022, 51(3):1125-1135.
DOI: 10.12442/j.issn.1002-185X.20210234
Abstract:
Additive manufacturing technology (3D printing) is an important development direction of advanced manufacturing technology, which has been applied to aerospace, automotive industry, biomedicine and other important fields. Since the first exfoliation of single-layer graphene in 2004, graphene and other two-dimensional crystal materials have gradually become a research hotspot in the field of composite materials. Its excellent mechanical properties and conductivity make it more suitable for reinforced phase materials. By adjusting the content and distribution of graphene reinforcement phase, the mechanical strength, conductivity and other properties of metal matrix materials can be greatly improved, and excellent structure function integrated materials can be obtained. Laser additive manufacturing technology combined with the advantages of high specific surface area and anisotropy of graphene nanosheets, further processing and mixing of graphene and metal powder, and then layer by layer printing to construct 3D structure, has become a new research direction, which is leading the progress of the fourth generation of industrial revolution. Based on laser additive manufacturing technology, this paper summarizes the research progress of graphene based metal matrix composites prepared by laser additive manufacturing technology from three aspects, that is, graphene based aluminum, nickel and other metal matrix composites prepared by laser additive manufacturing technology. The forming process and material properties are compared, and the possible development direction in the future is analyzed.
Additive manufacturing technology (3D printing) is an important development direction of advanced manufacturing technology, which has been applied to aerospace, automotive industry, biomedicine and other important fields. Since the first exfoliation of single-layer graphene in 2004, graphene and other two-dimensional crystal materials have gradually become a research hotspot in the field of composite materials. Its excellent mechanical properties and conductivity make it more suitable for reinforced phase materials. By adjusting the content and distribution of graphene reinforcement phase, the mechanical strength, conductivity and other properties of metal matrix materials can be greatly improved, and excellent structure function integrated materials can be obtained. Laser additive manufacturing technology combined with the advantages of high specific surface area and anisotropy of graphene nanosheets, further processing and mixing of graphene and metal powder, and then layer by layer printing to construct 3D structure, has become a new research direction, which is leading the progress of the fourth generation of industrial revolution. Based on laser additive manufacturing technology, this paper summarizes the research progress of graphene based metal matrix composites prepared by laser additive manufacturing technology from three aspects, that is, graphene based aluminum, nickel and other metal matrix composites prepared by laser additive manufacturing technology. The forming process and material properties are compared, and the possible development direction in the future is analyzed.
2022, 51(3):1136-1140.
DOI: 10.12442/j.issn.1002-185X.20210697
Abstract:
A new kind of AlNiLaCe high entropy metallic glasses (denoted as HE-MGs) ribbons were prepared by arc melting and melt spinning. The effects of (AlNi) / (LaCe) ratio on the microstructure and electrochemical corrosion behavior of HE-MGs were studied. The phase structure, thermal stability and hardness of these ribbons were determined by X-ray diffraction (XRD), differential scanning calorimeter (DSC) and Vickers hardness tester. The surface morphology and corresponding element distribution of these ribbons were characterized by scanning electron microscope (SEM) and energy dispersive X-ray spectrum (EDS). The electrochemical corrosion behavior of several AlNiLaCe HE-MGs ribbons in 3.5 wt.% NaCl solution was investigated by polarization curve (Tafel), and the corrosion products of Al25Ni25La25Ce25 ribbons were tested by XRD. The results show that with the increase of Al content, AlNiLaCe high entropy amorphous alloy ribbons are mainly comprised of amorphous phase and Al-rich intermetallic compounds. The increase of (AlNi) content in the alloy ribbons leads to the gradual improvement of their thermal stability and hardness. The maximum hardness of Al35Ni35La15Ce15 high entropy amorphous alloy ribbons is about 470 HV0.1. Through electrochemical corrosion experiments, it is found that compared with AZ91 magnesium alloy, the corrosion potential of AlNiLaCe alloy ribbons is higher and the current density is one order of magnitude lower than that of magnesium alloy.
A new kind of AlNiLaCe high entropy metallic glasses (denoted as HE-MGs) ribbons were prepared by arc melting and melt spinning. The effects of (AlNi) / (LaCe) ratio on the microstructure and electrochemical corrosion behavior of HE-MGs were studied. The phase structure, thermal stability and hardness of these ribbons were determined by X-ray diffraction (XRD), differential scanning calorimeter (DSC) and Vickers hardness tester. The surface morphology and corresponding element distribution of these ribbons were characterized by scanning electron microscope (SEM) and energy dispersive X-ray spectrum (EDS). The electrochemical corrosion behavior of several AlNiLaCe HE-MGs ribbons in 3.5 wt.% NaCl solution was investigated by polarization curve (Tafel), and the corrosion products of Al25Ni25La25Ce25 ribbons were tested by XRD. The results show that with the increase of Al content, AlNiLaCe high entropy amorphous alloy ribbons are mainly comprised of amorphous phase and Al-rich intermetallic compounds. The increase of (AlNi) content in the alloy ribbons leads to the gradual improvement of their thermal stability and hardness. The maximum hardness of Al35Ni35La15Ce15 high entropy amorphous alloy ribbons is about 470 HV0.1. Through electrochemical corrosion experiments, it is found that compared with AZ91 magnesium alloy, the corrosion potential of AlNiLaCe alloy ribbons is higher and the current density is one order of magnitude lower than that of magnesium alloy.
2022, 51(3):1141-1144.
DOI: 10.12442/j.issn.1002-185X.20210725
Abstract:
GH3039 has been extensively used in aeronautic industries. Poor machinability and low material usage are common in GH3039 components, which could be resolved by frabricated by additive manufacturing. In this study, a GH3039 thin wall part was fabricated by gas metal arc welding wire arc additive manufacturing (GMAW-WAAM). Optical microscope (OM) observation, microhardness indentation and tensile tests were applied to investigate the microstructure and mechanical properties of the part. Result shows that the defect-free dense part is mainly consisted of interlayer fine grain and coarse column grain, which grew vertically. The ambient temperature ultimate tensile strength (UTS) and fracture elongation (El) of the as deposited part are 520~540MPa and 36~40%, respectively. The elevated temperature (800°C) UTS and El along the deposition direction is 189MPa and 35.4%, respectively. This study verified the feasibility of manufacturing GH3039 part by GMAW-WAAM.
GH3039 has been extensively used in aeronautic industries. Poor machinability and low material usage are common in GH3039 components, which could be resolved by frabricated by additive manufacturing. In this study, a GH3039 thin wall part was fabricated by gas metal arc welding wire arc additive manufacturing (GMAW-WAAM). Optical microscope (OM) observation, microhardness indentation and tensile tests were applied to investigate the microstructure and mechanical properties of the part. Result shows that the defect-free dense part is mainly consisted of interlayer fine grain and coarse column grain, which grew vertically. The ambient temperature ultimate tensile strength (UTS) and fracture elongation (El) of the as deposited part are 520~540MPa and 36~40%, respectively. The elevated temperature (800°C) UTS and El along the deposition direction is 189MPa and 35.4%, respectively. This study verified the feasibility of manufacturing GH3039 part by GMAW-WAAM.
