Volume 50,Issue 11,2021 Table of Contents
2021, 50(11):3819-3823.
DOI: 10.12442/j.issn.1002-185X.20200976
Abstract:
Electron backscatter diffraction (EBSD) technique was used to analyze the microstructure of cold-rolled C71500 cupronickel alloy tube. Through the analysis of microhardness, tensile properties, microstructure, texture, and texture content of the cupronickel alloy tube after the second pass cold rolling with different deformations (3.19%, 9.57%, 19.37%, 23.97%, 31.78%), the texture change law of the alloy was obtained. The quantitative relationship between deformation and storage energy was revealed by analyzing the grain size and the change of texture and grain boundary, which could be directly reflected by the proportion of small angle grain boundaries. The optimal deformation of second pass rolling for C71500 alloy was obtained. Results show that the yield strength, tensile strength, and microhardness of cupronickel alloy are increased with increasing the working ratio, while the plasticity is decreased.
Electron backscatter diffraction (EBSD) technique was used to analyze the microstructure of cold-rolled C71500 cupronickel alloy tube. Through the analysis of microhardness, tensile properties, microstructure, texture, and texture content of the cupronickel alloy tube after the second pass cold rolling with different deformations (3.19%, 9.57%, 19.37%, 23.97%, 31.78%), the texture change law of the alloy was obtained. The quantitative relationship between deformation and storage energy was revealed by analyzing the grain size and the change of texture and grain boundary, which could be directly reflected by the proportion of small angle grain boundaries. The optimal deformation of second pass rolling for C71500 alloy was obtained. Results show that the yield strength, tensile strength, and microhardness of cupronickel alloy are increased with increasing the working ratio, while the plasticity is decreased.
2 Preparation of Magnéli Phase Ti n O2 n -1 by Carbothermal Reduction Sieving Method in Air Atmosphere
2021, 50(11):3824-3827.
DOI: 10.12442/j.issn.1002-185X.20201007
Abstract:
A novel method for fabricating Magnéli phase (MP) TinO2n-1 (4<n<10), carbothermal reduction sieving, in air atmosphere was introduced. The influence of the reduction temperature and reduction time on the phase structure and resistivity of reduction product was investigated. The results show that increasing the reduction temperature and prolonging the reduction time are beneficial for the reduction of TiO2 to MP TinO2n-1. MP TinO2n-1 (n=4, 5) powder was obtained after reduction at 1350 °C for 20 min, and its particle size is 0.5~8 μm according to results of scanning electron microscopy analysis. Resistivity of the reduction product is decreased significantly with prolonging the reduction time at 1350 °C. The minimum resistivity of 79.3 Ω?cm is achieved for the product after reduction at 1350 °C for 50 min, and the phase composition is mainly Ti3O5.
A novel method for fabricating Magnéli phase (MP) TinO2n-1 (4<n<10), carbothermal reduction sieving, in air atmosphere was introduced. The influence of the reduction temperature and reduction time on the phase structure and resistivity of reduction product was investigated. The results show that increasing the reduction temperature and prolonging the reduction time are beneficial for the reduction of TiO2 to MP TinO2n-1. MP TinO2n-1 (n=4, 5) powder was obtained after reduction at 1350 °C for 20 min, and its particle size is 0.5~8 μm according to results of scanning electron microscopy analysis. Resistivity of the reduction product is decreased significantly with prolonging the reduction time at 1350 °C. The minimum resistivity of 79.3 Ω?cm is achieved for the product after reduction at 1350 °C for 50 min, and the phase composition is mainly Ti3O5.
He Haoran
,
Liu Qi
,
Bo Xinwei
,
Wang Xiaoyu
,
Wang Yanhui
,
Yao Zhiyuan
,
Han Xiaoyu
,
Liu Chengchao
2021, 50(11):3828-3836.
DOI: 10.12442/j.issn.1002-185X.20200678
Abstract:
(Ti, Mo)Si2/MoSi2 composite coatings were prepared on Mo substrate by the continuous deposition pack cementation method. The X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and thermody-namic calculation were used to characterize the composite coatings and to analyze the formation mechanism. The results show that the co-deposition process cannot achieve the titanium deposition effectively. The titanium-modified MoSi2 coatings can be prepared by a two-step deposition process of titanizing and siliconizing. The coatings contain three layers: the outer layer is (Ti, Mo)Si2 ternary compound layer; the second layer is MoSi2 layer; the layer between the MoSi2 and Mo substrate is the Mo5Si3 transition layer. The siliconizing temperature shows negligible effect on coating structure. The growth rate of titanium-modified MoSi2 coating is slightly lower than that of single MoSi2 coating. The growth of (Ti, Mo)Si2/MoSi2 composite coating is dominated by the inward diffusion of Ti and Si. Ti is concentrated on the outer layer of the coating. Si diffuses through the (Ti, Mo)Si2 compound layer and interacts with the substrate to form the MoSi2 layer and Mo5Si3 transition layer. In the titanizing process, the free state AlF3 is introduced by the reaction among pack mixtures. In the subsequent siliconizing process, a trace amount of Al in free state is precipitated in the form of Al3Mo phases in the (Ti, Mo)Si2 layer near the upper interface of MoSi2 layer. During the cyclic oxidation tests at 1200 °C, the (Ti, Mo)Si2/MoSi2 composite coatings do not lose mass obviously after exposure in oxidation atmosphere for 180 h. A dense composite oxide layer consisting of SiO2 and TiO2 can be formed by the oxidation of (Ti, Mo)Si2 phase. This composite oxide layer can fill the surface cracks of the coating and continuously block the oxygen diffusion, so the oxidation resistance of (Ti, Mo)Si2/MoSi2 composite coating in the periodic oxidation environment is far superior to that of the single MoSi2 coating.
(Ti, Mo)Si2/MoSi2 composite coatings were prepared on Mo substrate by the continuous deposition pack cementation method. The X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and thermody-namic calculation were used to characterize the composite coatings and to analyze the formation mechanism. The results show that the co-deposition process cannot achieve the titanium deposition effectively. The titanium-modified MoSi2 coatings can be prepared by a two-step deposition process of titanizing and siliconizing. The coatings contain three layers: the outer layer is (Ti, Mo)Si2 ternary compound layer; the second layer is MoSi2 layer; the layer between the MoSi2 and Mo substrate is the Mo5Si3 transition layer. The siliconizing temperature shows negligible effect on coating structure. The growth rate of titanium-modified MoSi2 coating is slightly lower than that of single MoSi2 coating. The growth of (Ti, Mo)Si2/MoSi2 composite coating is dominated by the inward diffusion of Ti and Si. Ti is concentrated on the outer layer of the coating. Si diffuses through the (Ti, Mo)Si2 compound layer and interacts with the substrate to form the MoSi2 layer and Mo5Si3 transition layer. In the titanizing process, the free state AlF3 is introduced by the reaction among pack mixtures. In the subsequent siliconizing process, a trace amount of Al in free state is precipitated in the form of Al3Mo phases in the (Ti, Mo)Si2 layer near the upper interface of MoSi2 layer. During the cyclic oxidation tests at 1200 °C, the (Ti, Mo)Si2/MoSi2 composite coatings do not lose mass obviously after exposure in oxidation atmosphere for 180 h. A dense composite oxide layer consisting of SiO2 and TiO2 can be formed by the oxidation of (Ti, Mo)Si2 phase. This composite oxide layer can fill the surface cracks of the coating and continuously block the oxygen diffusion, so the oxidation resistance of (Ti, Mo)Si2/MoSi2 composite coating in the periodic oxidation environment is far superior to that of the single MoSi2 coating.
2021, 50(11):3837-3844.
DOI: 10.12442/j.issn.1002-185X.20200679
Abstract:
Fe25Cr5Al alloys with and without rare earth (RE) elements La and Ce, namely Fe25Cr5Al-RE and Fe25Cr5Al alloys, were prepared and isothermal oxidation tests were conducted at 1100 °C. The morphology of oxide scale was observed by scanning electron microscope (SEM), and the oxidation product was identified by energy disperse spectroscopy (EDS) coupled with X-ray diffraction (XRD). Results show that after oxidation for 1, 20, and 300 h, the mass gain of Fe25Cr5Al alloys is 0.08, 0.84, and 4.41 mg·cm-2, but that of Fe25Cr5Al-RE alloys is 0.03, 0.35, and 0.92 mg·cm-2, respectively. The oxide scale of the two alloys consists of α-Al2O3. La and Ce promote the formation of compact and continuous oxide scale, which significantly improves the high temperature oxidation resistance of Fe25Cr5Al alloys. Moreover, RE oxide pegs can be observed at substrate/scale interface of Fe25Cr5Al-RE alloys, which makes the bond between substrate and scale tighter, thus enhancing the adhesion of the interface. There are RE oxides in oxide scale of Fe25Cr5Al-RE alloys, which effectively inhibits further oxidation of the alloys.
Fe25Cr5Al alloys with and without rare earth (RE) elements La and Ce, namely Fe25Cr5Al-RE and Fe25Cr5Al alloys, were prepared and isothermal oxidation tests were conducted at 1100 °C. The morphology of oxide scale was observed by scanning electron microscope (SEM), and the oxidation product was identified by energy disperse spectroscopy (EDS) coupled with X-ray diffraction (XRD). Results show that after oxidation for 1, 20, and 300 h, the mass gain of Fe25Cr5Al alloys is 0.08, 0.84, and 4.41 mg·cm-2, but that of Fe25Cr5Al-RE alloys is 0.03, 0.35, and 0.92 mg·cm-2, respectively. The oxide scale of the two alloys consists of α-Al2O3. La and Ce promote the formation of compact and continuous oxide scale, which significantly improves the high temperature oxidation resistance of Fe25Cr5Al alloys. Moreover, RE oxide pegs can be observed at substrate/scale interface of Fe25Cr5Al-RE alloys, which makes the bond between substrate and scale tighter, thus enhancing the adhesion of the interface. There are RE oxides in oxide scale of Fe25Cr5Al-RE alloys, which effectively inhibits further oxidation of the alloys.
2021, 50(11):3845-3856.
DOI: 10.12442/j.issn.1002-185X.20210217
Abstract:
The 2A14-T4 Al-alloy T-joints were prepared by stationary shoulder friction stir welding (SSFSW) at different welding speeds. A smooth T-joint surface was obtained with the optimized welding process parameters. The results show that the microstructure of weld nugget zone (WNZ) consists of fine equiaxed grains caused by full dynamic recrystallization. The average grain size of the second weld nugget zone (WNZ2) is the largest, that of the weld nugget overlap zone (WNOZ) is in the middle, and that of the first weld nugget zone (WNZ1) is the smallest. The recrystallization mechanism in WNZ is mainly the geometric dynamic recrystallization accompanied by partial continuous dynamic recrystallization. The weak {100}<001> texture is formed in the WNOZ after two times of stirring, and the weak {111}<110> texture appears in WNZ1 and WNZ2. The thermo-mechanically-affected zone (TMAZ) undergoes plastic deformation, while the heat-affected zone (HAZ) is only affected by weld thermal cycles. No plastic deformation or the dynamic recrystallization of grains occurs in HAZ. The hardness of WNZ is high, and the zone with the lowest hardness is located in HAZ which is close to TMAZ. With increasing the welding speed, the ultimate tensile strength is firstly increased and then decreased. The mixed brittle/ductile fracture dominates the fracture mode of skin and stiffener plates.
The 2A14-T4 Al-alloy T-joints were prepared by stationary shoulder friction stir welding (SSFSW) at different welding speeds. A smooth T-joint surface was obtained with the optimized welding process parameters. The results show that the microstructure of weld nugget zone (WNZ) consists of fine equiaxed grains caused by full dynamic recrystallization. The average grain size of the second weld nugget zone (WNZ2) is the largest, that of the weld nugget overlap zone (WNOZ) is in the middle, and that of the first weld nugget zone (WNZ1) is the smallest. The recrystallization mechanism in WNZ is mainly the geometric dynamic recrystallization accompanied by partial continuous dynamic recrystallization. The weak {100}<001> texture is formed in the WNOZ after two times of stirring, and the weak {111}<110> texture appears in WNZ1 and WNZ2. The thermo-mechanically-affected zone (TMAZ) undergoes plastic deformation, while the heat-affected zone (HAZ) is only affected by weld thermal cycles. No plastic deformation or the dynamic recrystallization of grains occurs in HAZ. The hardness of WNZ is high, and the zone with the lowest hardness is located in HAZ which is close to TMAZ. With increasing the welding speed, the ultimate tensile strength is firstly increased and then decreased. The mixed brittle/ductile fracture dominates the fracture mode of skin and stiffener plates.
2021, 50(11):3857-3861.
DOI: 10.12442/j.issn.1002-185X.20210231
Abstract:
The film removal mechanism of FB3-F silver brazing flux consisting of H3BO3, K2B4O7, and KF with the mass ratio of 7:10:3 was studied. Results show that K2B4O7 or KF cannot individually remove the oxide film on Q235 steel at 700 °C, and KF even accelerates the oxidation rate of steel surface at high temperature. H3BO3 can remove the oxide film at 700 °C, but the product possesses an obvious amorphous structure feature and poor fluidity. Furthermore, H3BO3 can react with KF at 700 °C, and the reaction product can remove the oxide film. Similarly, K2B4O7 can react with KF, but the product is hard. The mixture solder consisting of H3BO3, K2B4O7, and KF can react with the oxide film on surface of Q235 steel plate, and the reaction product presents obvious amorphous feature. The addition of KF transforms the nonreactive H3BO3-K2B4O7 binary system into the reactive KF-H3BO3-K2B4O7 ternary system at 700 °C. KF shows no corrosivity and promotes the removal of oxide film of steel plates in this ternary system.
The film removal mechanism of FB3-F silver brazing flux consisting of H3BO3, K2B4O7, and KF with the mass ratio of 7:10:3 was studied. Results show that K2B4O7 or KF cannot individually remove the oxide film on Q235 steel at 700 °C, and KF even accelerates the oxidation rate of steel surface at high temperature. H3BO3 can remove the oxide film at 700 °C, but the product possesses an obvious amorphous structure feature and poor fluidity. Furthermore, H3BO3 can react with KF at 700 °C, and the reaction product can remove the oxide film. Similarly, K2B4O7 can react with KF, but the product is hard. The mixture solder consisting of H3BO3, K2B4O7, and KF can react with the oxide film on surface of Q235 steel plate, and the reaction product presents obvious amorphous feature. The addition of KF transforms the nonreactive H3BO3-K2B4O7 binary system into the reactive KF-H3BO3-K2B4O7 ternary system at 700 °C. KF shows no corrosivity and promotes the removal of oxide film of steel plates in this ternary system.
2021, 50(11):3862-3870.
DOI: 10.12442/j.issn.1002-185X.20200680
Abstract:
The precipitation phase evolution and the aging response of TB17 titanium alloy, a new titanium alloy with ultra-high strength and toughness, were studied by X-ray diffraction, scanning electron microscope, transmission electron microscope, and Vickers hardness tests during isothermal aging process. The results show that β→β+ω phase transformation mainly happens at 350 °C, and the precipitated phase ω is the shape of fine granular. After aging treatment at 450 °C, the α phase is nucleated through the assistance nucleation of ω phase. The phase transformation of β→β+α occurs at 550 and 650 °C and the α phase exhibits lamellar structure. However, there are two types of α phase precipitated after aging at 550 and 650 °C for long time: the Burgers α (Type 1α) phase which satisfies the Burgers orientation relationship and the Type 2α phase which does not satisfy the Burgers orientation relationship. The Type 2α phase is a twin crystal phase nucleated on the {10
The precipitation phase evolution and the aging response of TB17 titanium alloy, a new titanium alloy with ultra-high strength and toughness, were studied by X-ray diffraction, scanning electron microscope, transmission electron microscope, and Vickers hardness tests during isothermal aging process. The results show that β→β+ω phase transformation mainly happens at 350 °C, and the precipitated phase ω is the shape of fine granular. After aging treatment at 450 °C, the α phase is nucleated through the assistance nucleation of ω phase. The phase transformation of β→β+α occurs at 550 and 650 °C and the α phase exhibits lamellar structure. However, there are two types of α phase precipitated after aging at 550 and 650 °C for long time: the Burgers α (Type 1α) phase which satisfies the Burgers orientation relationship and the Type 2α phase which does not satisfy the Burgers orientation relationship. The Type 2α phase is a twin crystal phase nucleated on the {10
2021, 50(11):3871-3878.
DOI: 10.12442/j.issn.1002-185X.20200663
Abstract:
The effects of micro-alloying treatment on corrosion resistance and mechanical properties of biomaterial magnesium alloy were investigated by optical microscope (OM), scanning electron microscope (SEM), immersion test, electrochemical test, and tensile test. The results show that after successively adding Zn, Zr, and Dy, the grain of magnesium alloys is refined and the second phase is generated and grows up. When Zn, Zr, and Dy are simultaneously added into magnesium alloy, the grain size of alloy is decreased from 1087 μm to 70 μm and the microstructure becomes more uniform. Moreover, the addition of Zn, Zr, and Dy significantly improves the corrosion resistance and mechanical properties of magnesium alloy: the corrosion rate decreases from 2.01 mm/a to 0.92 mm/a; the self-corrosion current density decreases from 4.22 μA/cm2 to 2.05 μA/cm2; the yield strength, ultimate tensile strength, and elongation increase from 30.5 MPa, 69.5 MPa, and 6% to 84 MPa, 154 MPa, and 8.6%, respectively.
The effects of micro-alloying treatment on corrosion resistance and mechanical properties of biomaterial magnesium alloy were investigated by optical microscope (OM), scanning electron microscope (SEM), immersion test, electrochemical test, and tensile test. The results show that after successively adding Zn, Zr, and Dy, the grain of magnesium alloys is refined and the second phase is generated and grows up. When Zn, Zr, and Dy are simultaneously added into magnesium alloy, the grain size of alloy is decreased from 1087 μm to 70 μm and the microstructure becomes more uniform. Moreover, the addition of Zn, Zr, and Dy significantly improves the corrosion resistance and mechanical properties of magnesium alloy: the corrosion rate decreases from 2.01 mm/a to 0.92 mm/a; the self-corrosion current density decreases from 4.22 μA/cm2 to 2.05 μA/cm2; the yield strength, ultimate tensile strength, and elongation increase from 30.5 MPa, 69.5 MPa, and 6% to 84 MPa, 154 MPa, and 8.6%, respectively.
Li Weirong
,
Dan Yun
,
Huang Xianxiang
,
Guan Renguo
,
Ren Haobo
,
Li Yangde
,
Sun Lijuan
,
Zhang Jin
,
Tie Di
2021, 50(11):3879-3884.
DOI: 10.12442/j.issn.1002-185X.20200667
Abstract:
The effect of different Sn contents on microstructure evolution, tensile behavior, and wear properties of AZ91 alloys by rheocasting was studied. The results show that the presence of Sn changes the solid solubility of Al in Mg matrix and effectively refines the microstructure of alloy matrix. The average grain size is refined from 105.0 μm to 42.1 μm after addition of 0.8wt% Sn. The heterogeneous precipitate nuclei are formed by the intermetallics with high melting point, which effectively refines the magnesium matrix during the rheo-solidification. These dispersed second phases suppress the formation of dendrites, further improving the mechanical properties. With increasing the Sn content, the wear rate of alloys is obviously decreased and the abrasive wear disappears gradually. The rheocast AZ91 alloy with addition of 3.0wt% Sn has the highest tensile strength and the best wear resistance.
The effect of different Sn contents on microstructure evolution, tensile behavior, and wear properties of AZ91 alloys by rheocasting was studied. The results show that the presence of Sn changes the solid solubility of Al in Mg matrix and effectively refines the microstructure of alloy matrix. The average grain size is refined from 105.0 μm to 42.1 μm after addition of 0.8wt% Sn. The heterogeneous precipitate nuclei are formed by the intermetallics with high melting point, which effectively refines the magnesium matrix during the rheo-solidification. These dispersed second phases suppress the formation of dendrites, further improving the mechanical properties. With increasing the Sn content, the wear rate of alloys is obviously decreased and the abrasive wear disappears gradually. The rheocast AZ91 alloy with addition of 3.0wt% Sn has the highest tensile strength and the best wear resistance.
2021, 50(11):3885-3889.
DOI: 10.12442/j.issn.1002-185X.E20200050
Abstract:
La0.4Sr0.6Co0.7Fe0.2Nb0.1O3-δ-Gd0.2Ce0.8O2-δ (LSCFN-GDC) with high catalytic performance was synthesized by one-step co-synthesis method for developing a symmetrical reversible solid oxide cell (SOC) electrode. Electrolyte-supported symmetrical SOCs were fabricated by tape-casting and screen-printing methods with La0.8Sr0.2Ga0.83Mg0.17O3-δ (LSGM) as the electrolyte and LSCFN-GDC as both anode and cathode. The configuration of SOC is LSCFN-GDC||LSGM||LSCFN-GDC. Solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) modes were used to test the performance of SOCs. The results show that the maximum power densities are 1.036, 0.996, 0.479, and 0.952 W/cm2 under the atmosphere of fuel gas of H2 (3% H2O), H2 (0.01% H2S), CH4, and C3H8 at 850 °C, respectively. The current density at the electrolytic voltage of 1.3 V is 0.943 A/cm2 during the electrolysis of H2 (50% H2O). LSCFN-GDC has good coking-resistance, sulfur-tolerance, and redox stability, and its stable performance can be sustained for 700 h under the atmosphere of H2 (0.01% H2S), CH4, H2 (3% H2O), and H2 (50% H2O). The results indicate that the one-step method is a facile and optimized fabrication procedure of electrode and LSCFN-GDC||LSGM||LSCFN-GDC SOCs have great potential in further application.
La0.4Sr0.6Co0.7Fe0.2Nb0.1O3-δ-Gd0.2Ce0.8O2-δ (LSCFN-GDC) with high catalytic performance was synthesized by one-step co-synthesis method for developing a symmetrical reversible solid oxide cell (SOC) electrode. Electrolyte-supported symmetrical SOCs were fabricated by tape-casting and screen-printing methods with La0.8Sr0.2Ga0.83Mg0.17O3-δ (LSGM) as the electrolyte and LSCFN-GDC as both anode and cathode. The configuration of SOC is LSCFN-GDC||LSGM||LSCFN-GDC. Solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) modes were used to test the performance of SOCs. The results show that the maximum power densities are 1.036, 0.996, 0.479, and 0.952 W/cm2 under the atmosphere of fuel gas of H2 (3% H2O), H2 (0.01% H2S), CH4, and C3H8 at 850 °C, respectively. The current density at the electrolytic voltage of 1.3 V is 0.943 A/cm2 during the electrolysis of H2 (50% H2O). LSCFN-GDC has good coking-resistance, sulfur-tolerance, and redox stability, and its stable performance can be sustained for 700 h under the atmosphere of H2 (0.01% H2S), CH4, H2 (3% H2O), and H2 (50% H2O). The results indicate that the one-step method is a facile and optimized fabrication procedure of electrode and LSCFN-GDC||LSGM||LSCFN-GDC SOCs have great potential in further application.
2021, 50(11):3890-3895.
DOI: 10.12442/j.issn.1002-185X.20200669
Abstract:
The SiC coating on carbon fiber was synthesized via an in-situ reaction method using silicon powder as silicon source, and the effect of reaction pressure on the synthesis, microstructure, and oxidation resistance of SiC coating was investigated. The results show that SiC coating synthesized at the atmospheric pressure is loose and porous; numerous SiC nanowires are formed on it. In comparison, the SiC coating synthesized at the low pressure is uniform and dense. The isothermal oxidation test shows that the SiC coating synthesized at the low pressure has better oxidation resistance than the one synthesized at the atmospheric pressure, because the dense and uniform SiC coating can prevent oxygen from contacting with carbon fiber more effectively. Based on the experiment results, the growth mechanism of SiC coating influenced by the reaction pressure was proposed. At the atmospheric pressure, the kinetic energies of deposition particles are too low to overcome the shadowing effect, causing the formation of porous SiC coating. By contrast, the deposition particles have higher kinetic energies and surface diffusion rate on the surface of carbon fiber at the low pressure, thereby forming a uniform and dense SiC coating.
The SiC coating on carbon fiber was synthesized via an in-situ reaction method using silicon powder as silicon source, and the effect of reaction pressure on the synthesis, microstructure, and oxidation resistance of SiC coating was investigated. The results show that SiC coating synthesized at the atmospheric pressure is loose and porous; numerous SiC nanowires are formed on it. In comparison, the SiC coating synthesized at the low pressure is uniform and dense. The isothermal oxidation test shows that the SiC coating synthesized at the low pressure has better oxidation resistance than the one synthesized at the atmospheric pressure, because the dense and uniform SiC coating can prevent oxygen from contacting with carbon fiber more effectively. Based on the experiment results, the growth mechanism of SiC coating influenced by the reaction pressure was proposed. At the atmospheric pressure, the kinetic energies of deposition particles are too low to overcome the shadowing effect, causing the formation of porous SiC coating. By contrast, the deposition particles have higher kinetic energies and surface diffusion rate on the surface of carbon fiber at the low pressure, thereby forming a uniform and dense SiC coating.
2021, 50(11):3896-3900.
DOI: 10.12442/j.issn.1002-185X.20200639
Abstract:
The alumina coatings as a tritium-resistance coating were deposited on 316L stainless steel by ion implantation. The effects of different parameters of ion implantation process on the wear resistance, corrosion resistance, thermal shock resistance, and tritium permeation resistance of α-Al2O3 were investigated. Results show that the content of α-Al2O3 is affected by temperature, acceleration voltage, and ion implantation dose. With increasing the temperature, the content of α-Al2O3 is increased. With increasing the acceleration voltage or ion implantation dose, the content of α-Al2O3 is firstly increased and then decreased. The wear resistance and corrosion resistance are mainly affected by the ion implantation dose: with increasing the ion implantation dose, the wear and corrosion resistance becomes better. The Al2O3 coatings hardly changes after 200 times of thermal shock tests, indicating a good thermal shock resistance. The tritium permeability of the coated specimen is reduced by 3 orders of magnitude, compared with that of the 316L stainless steel bulk.
The alumina coatings as a tritium-resistance coating were deposited on 316L stainless steel by ion implantation. The effects of different parameters of ion implantation process on the wear resistance, corrosion resistance, thermal shock resistance, and tritium permeation resistance of α-Al2O3 were investigated. Results show that the content of α-Al2O3 is affected by temperature, acceleration voltage, and ion implantation dose. With increasing the temperature, the content of α-Al2O3 is increased. With increasing the acceleration voltage or ion implantation dose, the content of α-Al2O3 is firstly increased and then decreased. The wear resistance and corrosion resistance are mainly affected by the ion implantation dose: with increasing the ion implantation dose, the wear and corrosion resistance becomes better. The Al2O3 coatings hardly changes after 200 times of thermal shock tests, indicating a good thermal shock resistance. The tritium permeability of the coated specimen is reduced by 3 orders of magnitude, compared with that of the 316L stainless steel bulk.
2021, 50(11):3901-3909.
DOI: 10.12442/j.issn.1002-185X.E20200042
Abstract:
The relationship between the optical emission spectroscopy and the microstructure of CoCrMoW coatings by laser melting deposition was investigated. The relationship between the primary dendrite spacing and microhardness of CoCrMoW coatings at different laser powers of spectral signal was studied. A new spectral signal index, the integral area, was proposed, and the electron temperature was calculated from four discrete Cr I spectral lines. The results show that with increasing the laser power from 400 W to 1000 W, the average primary dendrite spacing is increased from 3.426 μm to 7.420 μm, and the microhardness HV0.2 is reduced from 3461 MPa to 3095 MPa. The integral area and electron temperature of the spectral is also increased with increasing the laser power. The primary dendrite spacing of the coating is positively linear-related with the spectral signal, while the microhardness of the coatings is negatively linear-related with the spectral signal. In this research, compared with the electron temperature, the integral area shows a better potential for the prediction of the primary dendrite spacing and microhardness of coatings.
The relationship between the optical emission spectroscopy and the microstructure of CoCrMoW coatings by laser melting deposition was investigated. The relationship between the primary dendrite spacing and microhardness of CoCrMoW coatings at different laser powers of spectral signal was studied. A new spectral signal index, the integral area, was proposed, and the electron temperature was calculated from four discrete Cr I spectral lines. The results show that with increasing the laser power from 400 W to 1000 W, the average primary dendrite spacing is increased from 3.426 μm to 7.420 μm, and the microhardness HV0.2 is reduced from 3461 MPa to 3095 MPa. The integral area and electron temperature of the spectral is also increased with increasing the laser power. The primary dendrite spacing of the coating is positively linear-related with the spectral signal, while the microhardness of the coatings is negatively linear-related with the spectral signal. In this research, compared with the electron temperature, the integral area shows a better potential for the prediction of the primary dendrite spacing and microhardness of coatings.
2021, 50(11):3910-3916.
DOI: 10.12442/j.issn.1002-185X.20200686
Abstract:
The Al-Zn-Mg-Cu alloy with high Zn content was cast at different temperature gradients by directional solidification. The primary dendrite arm spacing λ1, the secondary dendrite arm spacing λ2, and the Vickers hardness of specimens were characterized. Based on the experiment results, the relationship among temperature gradient, dendritic arm spacing, and microhardness was determined by linear regression analysis and curve fitting analysis. The results are in agreement with the dendritic growth theoretical models, and the solidification parameters of Al-Zn-Mg-Cu alloy were obtained. In addition, the influence mechanism of temperature gradient on microhardness was analyzed. The results have a guidance function on the optimization of preparing methods of Al-Zn-Mg-Cu alloy with high zinc content.
The Al-Zn-Mg-Cu alloy with high Zn content was cast at different temperature gradients by directional solidification. The primary dendrite arm spacing λ1, the secondary dendrite arm spacing λ2, and the Vickers hardness of specimens were characterized. Based on the experiment results, the relationship among temperature gradient, dendritic arm spacing, and microhardness was determined by linear regression analysis and curve fitting analysis. The results are in agreement with the dendritic growth theoretical models, and the solidification parameters of Al-Zn-Mg-Cu alloy were obtained. In addition, the influence mechanism of temperature gradient on microhardness was analyzed. The results have a guidance function on the optimization of preparing methods of Al-Zn-Mg-Cu alloy with high zinc content.
2021, 50(11):3917-3923.
DOI: 10.12442/j.issn.1002-185X.20200647
Abstract:
In order to optimize the actuating performance of single layer surface acoustic wave interdigital transducer (SAW-IDT) and to improve the deficiencies of calculation process of the δ function analysis method, the static properties of the SAW-IDT were analyzed by the finite element simulation optimization method. The influence of the width of the branch electrodes (w), the electrodes interval (s), and the thickness of the substrate (t) on the actuating performance of SAW-IDT was investigated. The simulation results show that when w/t=0.7, the optimal strain response can be obtained; when s/t>3.2, the maximum strain can be obtained. Besides, it can also be concluded that the smaller the electrode interval, the lower the actuating voltage. According to the simulated optimization results, a SAW-IDT was prepared and the frequency response was tested by experiments. The results provide a guidance for the preparation, performance testing, and application of SAW-IDT.
In order to optimize the actuating performance of single layer surface acoustic wave interdigital transducer (SAW-IDT) and to improve the deficiencies of calculation process of the δ function analysis method, the static properties of the SAW-IDT were analyzed by the finite element simulation optimization method. The influence of the width of the branch electrodes (w), the electrodes interval (s), and the thickness of the substrate (t) on the actuating performance of SAW-IDT was investigated. The simulation results show that when w/t=0.7, the optimal strain response can be obtained; when s/t>3.2, the maximum strain can be obtained. Besides, it can also be concluded that the smaller the electrode interval, the lower the actuating voltage. According to the simulated optimization results, a SAW-IDT was prepared and the frequency response was tested by experiments. The results provide a guidance for the preparation, performance testing, and application of SAW-IDT.
2021, 50(11):3924-3933.
DOI: 10.12442/j.issn.1002-185X.E20200044
Abstract:
Based on the hot compression test data of as-cast AZ80 magnesium alloy under the conditions of deformation temperature of 250~400 °C and strain rate of 0.001~1 s-1, a physical-based constitutive model based on the stress dislocation correlation and dynamic recrystallization dynamics and an artificial neural network (ANN) model based on feedforward backpropagation algorithm were established to predict the thermal deformation behavior of AZ80 magnesium alloy. Three statistical indicators, correlation coefficient (R), mean absolute relative error (AARE), and relative error (RE), were used to verify the prediction accuracy of these two models. The results show that both the models can accurately predict the thermal deformation behavior of AZ80 magnesium alloy. The stress value predicted by ANN model shows better agreement with the experimental data, and the value of R and AARE of ANN model is 0.9991 and 2.02%, respectively. While the R and AARE predicted by the physical-based constitutive model are 0.9936 and 4.52%, respectively. The better predictive ability of ANN model is attributed to its ability to deal with complex nonlinear relationships, while the predictive ability of the physical-based constitutive model is attributed to the fact that the model has certain physical meaning. The thermodynamic mechanism of work hardening (WH), dynamic recovery (DRV), and dynamic recrystallization (DRX) during thermal deformation are fully considered in the model parameters. Finally, the advantages and disadvantages of these two models are compared and discussed.
Based on the hot compression test data of as-cast AZ80 magnesium alloy under the conditions of deformation temperature of 250~400 °C and strain rate of 0.001~1 s-1, a physical-based constitutive model based on the stress dislocation correlation and dynamic recrystallization dynamics and an artificial neural network (ANN) model based on feedforward backpropagation algorithm were established to predict the thermal deformation behavior of AZ80 magnesium alloy. Three statistical indicators, correlation coefficient (R), mean absolute relative error (AARE), and relative error (RE), were used to verify the prediction accuracy of these two models. The results show that both the models can accurately predict the thermal deformation behavior of AZ80 magnesium alloy. The stress value predicted by ANN model shows better agreement with the experimental data, and the value of R and AARE of ANN model is 0.9991 and 2.02%, respectively. While the R and AARE predicted by the physical-based constitutive model are 0.9936 and 4.52%, respectively. The better predictive ability of ANN model is attributed to its ability to deal with complex nonlinear relationships, while the predictive ability of the physical-based constitutive model is attributed to the fact that the model has certain physical meaning. The thermodynamic mechanism of work hardening (WH), dynamic recovery (DRV), and dynamic recrystallization (DRX) during thermal deformation are fully considered in the model parameters. Finally, the advantages and disadvantages of these two models are compared and discussed.
2021, 50(11):3934-3941.
DOI: 10.12442/j.issn.1002-185X.E20200045
Abstract:
The thermal shock behavior of molybdenum disilicide (MoSi2)/molybdenum (Mo) coating and the crack propagation were evaluated by heating the coating to 1000 °C, and then cooling it down to room temperature under the protection atmosphere of hydrogen during the thermal shock cycle. Meanwhile the thermal stress distribution of MoSi2/Mo coating during thermal shock was calculated by Abaqus software. The development process of crack during thermal shock cycles was discussed. The results show that there is a high thermal shock stress between the Mo substrate and MoSi2 coating, which can lead to the crack initiation and propagation. According to the extended finite element simulation results, the cracks appear perpendicular to the interface during the first ten thermal shock cycles, while the coating is still well bonded with the substrate and shows no signs of crack along the interface. The interfacial crack appears in the subsequent thermal shock cycles. The interfacial crack begins at the end zone of the vertical crack. When the vertical crack and the interfacial crack converge, the coating peels off and the coating failure occurs.
The thermal shock behavior of molybdenum disilicide (MoSi2)/molybdenum (Mo) coating and the crack propagation were evaluated by heating the coating to 1000 °C, and then cooling it down to room temperature under the protection atmosphere of hydrogen during the thermal shock cycle. Meanwhile the thermal stress distribution of MoSi2/Mo coating during thermal shock was calculated by Abaqus software. The development process of crack during thermal shock cycles was discussed. The results show that there is a high thermal shock stress between the Mo substrate and MoSi2 coating, which can lead to the crack initiation and propagation. According to the extended finite element simulation results, the cracks appear perpendicular to the interface during the first ten thermal shock cycles, while the coating is still well bonded with the substrate and shows no signs of crack along the interface. The interfacial crack appears in the subsequent thermal shock cycles. The interfacial crack begins at the end zone of the vertical crack. When the vertical crack and the interfacial crack converge, the coating peels off and the coating failure occurs.
2021, 50(11):3942-3948.
DOI: 10.12442/j.issn.1002-185X.20210313
Abstract:
The relaxed structures and electromagnetism properties of Fe nanobelts with different cross-sections of 3×5, 3×7, 3×9, 3×11, 3×13, and 3×15 atom layers were investigated using the first-principles of projector-augmented wave (PAW) pseudo potential based on the density functional theory (DFT) framework. Results show that for all the Fe nanobelts, the relaxed structures retain the two-fold symmetry. However, the cross-section changes from rectangle shape in the beginning into a near-single-ellipse shape for the ones with atom layers of 3×5 and 3×7, and into a double-ellipse shape for other atom layers with broader cross-sections. In addition, it is found that the Fe nanobelt with 3×7 atom layer is a half-metal material: electrons with either majority spin or minority spin can pass through the Fermi level. Therefore, it can be used in the field of spintronics for producing nearly 100% spin-polarized currents.
The relaxed structures and electromagnetism properties of Fe nanobelts with different cross-sections of 3×5, 3×7, 3×9, 3×11, 3×13, and 3×15 atom layers were investigated using the first-principles of projector-augmented wave (PAW) pseudo potential based on the density functional theory (DFT) framework. Results show that for all the Fe nanobelts, the relaxed structures retain the two-fold symmetry. However, the cross-section changes from rectangle shape in the beginning into a near-single-ellipse shape for the ones with atom layers of 3×5 and 3×7, and into a double-ellipse shape for other atom layers with broader cross-sections. In addition, it is found that the Fe nanobelt with 3×7 atom layer is a half-metal material: electrons with either majority spin or minority spin can pass through the Fermi level. Therefore, it can be used in the field of spintronics for producing nearly 100% spin-polarized currents.
2021, 50(11):3949-3956.
DOI: 10.12442/j.issn.1002-185X.20200923
Abstract:
In this study, we used a virtual crystal approximation (VCA) method based on the first-principle density functional theory and the generalized gradient approximation (GGA) form to establish a body centered cubic structure model of NbTaTiZr alloys. In order to provide a theoretic basis for optimizing the NbTaTiZr alloy according to the requirement of orthopedic implant materials, we computed the structural and mechanical properties of the model alloys including elasticity, anisotropy, hardness and wear resistance, and the influence of the components on these properties. The results show that Nb and Ta can improve the ductility and bond properties of the alloys. The increase of Ti element content is conducive to the reduction of Young"s modulus and shear modulus of the multi-component alloy, which significantly improves the plasticity of the alloy. We also found that However, in order to match the alloys to the natural bone in terms of Poisson"s ratio, the content of Ti should be strictly controlled. The influence of Ta, Nb, Zr and Ti on the anisotropy of the alloy enhances successively. The Poisson’s ratio of NbTa1.4TiZr alloy is comparable to that of the ultrahigh molecular weight polyethylene (UHMWPE) used for artificial hip joint and most close to the micro-hardness of human cortical bone.
In this study, we used a virtual crystal approximation (VCA) method based on the first-principle density functional theory and the generalized gradient approximation (GGA) form to establish a body centered cubic structure model of NbTaTiZr alloys. In order to provide a theoretic basis for optimizing the NbTaTiZr alloy according to the requirement of orthopedic implant materials, we computed the structural and mechanical properties of the model alloys including elasticity, anisotropy, hardness and wear resistance, and the influence of the components on these properties. The results show that Nb and Ta can improve the ductility and bond properties of the alloys. The increase of Ti element content is conducive to the reduction of Young"s modulus and shear modulus of the multi-component alloy, which significantly improves the plasticity of the alloy. We also found that However, in order to match the alloys to the natural bone in terms of Poisson"s ratio, the content of Ti should be strictly controlled. The influence of Ta, Nb, Zr and Ti on the anisotropy of the alloy enhances successively. The Poisson’s ratio of NbTa1.4TiZr alloy is comparable to that of the ultrahigh molecular weight polyethylene (UHMWPE) used for artificial hip joint and most close to the micro-hardness of human cortical bone.
2021, 50(11):3957-3965.
DOI: 10.12442/j.issn.1002-185X.20200871
Abstract:
A multi-scale study of the dynamic grain refinement behavior and residual stress state of copper induced by surface mechanical attrition treatment (SMAT) of copper was carried out by developing a macro-micro coupled simulation method. The three-dimensional macro-scale finite element model of SMAT was developed firstly, and the refined grain size was calculated accordingly. According to the averaged grain size, the finite element model of polycrystals was created, the dislocation slip resistance resulted from the macro-scale finite element computation of SMAT was imported into the crystal plastic constitutive model, and the strain field outputted from the macro-scale finite element simulation was converted into the displacement boundary condition and was imposed on the finite element model of copper polycrystals. The crystal plastic finite element computation was then performed with respect to the present material hardening effect. The microstructure stress state and grain orientation distribution within a material point of the macro-scale finite element model of SMAT were resultantly investigated by using the micro-scale finite element model of polycrystals. The obtained results show that, during the SMAT process, with the increasing of shot multi-directional impacts, the refined grain size decreases and both the macroscale and microscale surface compressive residual stresses increase, however, the non-uniformity of the grain orientation distribution increases at first and then decreases gradually.
A multi-scale study of the dynamic grain refinement behavior and residual stress state of copper induced by surface mechanical attrition treatment (SMAT) of copper was carried out by developing a macro-micro coupled simulation method. The three-dimensional macro-scale finite element model of SMAT was developed firstly, and the refined grain size was calculated accordingly. According to the averaged grain size, the finite element model of polycrystals was created, the dislocation slip resistance resulted from the macro-scale finite element computation of SMAT was imported into the crystal plastic constitutive model, and the strain field outputted from the macro-scale finite element simulation was converted into the displacement boundary condition and was imposed on the finite element model of copper polycrystals. The crystal plastic finite element computation was then performed with respect to the present material hardening effect. The microstructure stress state and grain orientation distribution within a material point of the macro-scale finite element model of SMAT were resultantly investigated by using the micro-scale finite element model of polycrystals. The obtained results show that, during the SMAT process, with the increasing of shot multi-directional impacts, the refined grain size decreases and both the macroscale and microscale surface compressive residual stresses increase, however, the non-uniformity of the grain orientation distribution increases at first and then decreases gradually.
Li Xiaolong
,
Zhou Chunsheng
,
Yang Chaopu
,
Li Zhejian
,
Di Youying
,
Li Feng
,
Wang Qingyu
,
Guo Ming
2021, 50(11):3966-3970.
DOI: 10.12442/j.issn.1002-185X.20200857
Abstract:
Following the bottom-up technology, the flower-shaped nanomaterials consisted of nanobelts and nanowirs were fabricated on ITO-coated glass substrate by electrodeposition. The morphology of the as-prepared nano-flower was analized by FE-SEM. Moreover, the forming process was simulated. The results showed that the nano-flowers were fabricated through the two steps: first, nanowires formed gradually into nanobelts during the couse of thermal treatment; second, nanobelts contracted into nano-flowers. In addition, the conditions of thermal treatment played the determined role on the flower-shaped Bi2Te2.7Se0.3thermoelectric materials.
Following the bottom-up technology, the flower-shaped nanomaterials consisted of nanobelts and nanowirs were fabricated on ITO-coated glass substrate by electrodeposition. The morphology of the as-prepared nano-flower was analized by FE-SEM. Moreover, the forming process was simulated. The results showed that the nano-flowers were fabricated through the two steps: first, nanowires formed gradually into nanobelts during the couse of thermal treatment; second, nanobelts contracted into nano-flowers. In addition, the conditions of thermal treatment played the determined role on the flower-shaped Bi2Te2.7Se0.3thermoelectric materials.
2021, 50(11):3971-3978.
DOI: 10.12442/j.issn.1002-185X.20210178
Abstract:
Bulk YbxCo4Sb12 (x=0.27, 0.28, 0.29) alloy samples were prepared by melt-annealing-discharge plasma sintering. XRD, SEM and EDS analysis show that Yb doped single phase CoSb3 thermoelectric material has been successfully synthesized. When the Yb content increases from 0.27 to 0.29, the power factor of the material increases first and then decreases with the increase of temperature, while the thermal conductivity decreases first and then increases. Due to the relatively high power factor of 1815 μWm-1K-2 and the relatively low thermal conductivity of 2.23Wm-1K-1, the alloy Yb0.29Co4Sb12 obtained a higher ZT value of 0.62 at 773K. The Al-Ni protective coating of Yb0.29Co4Sb12 was sputtered by magnetron sputtering method. SEM and EDS showed that the coating bonded well with the substrate, and the thermoelectric properties of Yb0.29Co4Sb12 element protected by coating had good stability. The welding behavior of the joint between Yb0.29Co4Sb12 and electrode Mo50Cu50 was studied by Ag40Cu60 solder. It was found that the interface was well bonded, and no serious diffusion of Co, Sb, Yb, Mo and other elements occurred at the interface.
Bulk YbxCo4Sb12 (x=0.27, 0.28, 0.29) alloy samples were prepared by melt-annealing-discharge plasma sintering. XRD, SEM and EDS analysis show that Yb doped single phase CoSb3 thermoelectric material has been successfully synthesized. When the Yb content increases from 0.27 to 0.29, the power factor of the material increases first and then decreases with the increase of temperature, while the thermal conductivity decreases first and then increases. Due to the relatively high power factor of 1815 μWm-1K-2 and the relatively low thermal conductivity of 2.23Wm-1K-1, the alloy Yb0.29Co4Sb12 obtained a higher ZT value of 0.62 at 773K. The Al-Ni protective coating of Yb0.29Co4Sb12 was sputtered by magnetron sputtering method. SEM and EDS showed that the coating bonded well with the substrate, and the thermoelectric properties of Yb0.29Co4Sb12 element protected by coating had good stability. The welding behavior of the joint between Yb0.29Co4Sb12 and electrode Mo50Cu50 was studied by Ag40Cu60 solder. It was found that the interface was well bonded, and no serious diffusion of Co, Sb, Yb, Mo and other elements occurred at the interface.
2021, 50(11):3979-3986.
DOI: 10.12442/j.issn.1002-185X.20210346
Abstract:
The characteristics of superalloy powders used for the gradient integral turbine blisk by the hyper-transient solidified additive manufacturing are investigated. According to the temperature capacity of the alloy and the phase equilibrium diagram calculated by JMatPro, DZ4125 is selected as the blade material, whereas K418 alloys are selected as the disk rim material for integral turbine blisk. The superalloy powder are prepared by vacuum induction melting and argon gas atomization (VIGA) and sieved to the particle size range of 53-105μm. The differential scanning calorimeter (DSC), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), laser diffraction particle size analyzer, dynamic image analysis system and comprehensive powder property analyzer are used to systematically characterize the phase transformation temperatures, microstructure, precipitated phase composition, element segregation, particle size and shape, apparent density, tap density and flowability of the selected superalloy powders. The results show that DZ4125 possesses wider solid-liquid temperature range than that of K418 alloy. The liquidus temperature and MC carbide initial precipitation temperature of the transition zone DZ4125+K418 hybrid composition alloy are between that of the two alloys, and the γ" onset precipitation temperature is equivalent to the two alloys. The morphology of DZ4125 alloy powders is mainly spherical and nearly spherical. The surface and cross-section microstructures are mainly dendritic structure. For the selected alloy powders, the elements Hf，Ta, Ti, Mo and W exhibit strong segregation tendency, while the elements with weak segregation tendency include Ni, Cr, Co and Al. There are fine MC carbides distributed in the interdendritic zone of the powder, the size is about 200nm. The particle size distribution of powders measured by laser diffraction and dynamic image analysis methods are similar. The D50 value of DZ4125 powder is 70.2μm and 72.8μm. The dynamic image analysis result shows that the DZ4125 alloy powders possess good sphericity, and the SPHT and b/l values are 0.91 and 0.86, respectively. The DZ4125 superalloy powders have good apparent density, tap density and flowablity. The apparent density and tap density of the alloy powders can reach 52% and 63% of the theoretical density of the DZ4125 alloy, respectively. In addition, the DZ4125 superalloy powders possess compressibility of 17.7% and flowability of 20.79 s?(50 g)-1.
The characteristics of superalloy powders used for the gradient integral turbine blisk by the hyper-transient solidified additive manufacturing are investigated. According to the temperature capacity of the alloy and the phase equilibrium diagram calculated by JMatPro, DZ4125 is selected as the blade material, whereas K418 alloys are selected as the disk rim material for integral turbine blisk. The superalloy powder are prepared by vacuum induction melting and argon gas atomization (VIGA) and sieved to the particle size range of 53-105μm. The differential scanning calorimeter (DSC), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), laser diffraction particle size analyzer, dynamic image analysis system and comprehensive powder property analyzer are used to systematically characterize the phase transformation temperatures, microstructure, precipitated phase composition, element segregation, particle size and shape, apparent density, tap density and flowability of the selected superalloy powders. The results show that DZ4125 possesses wider solid-liquid temperature range than that of K418 alloy. The liquidus temperature and MC carbide initial precipitation temperature of the transition zone DZ4125+K418 hybrid composition alloy are between that of the two alloys, and the γ" onset precipitation temperature is equivalent to the two alloys. The morphology of DZ4125 alloy powders is mainly spherical and nearly spherical. The surface and cross-section microstructures are mainly dendritic structure. For the selected alloy powders, the elements Hf，Ta, Ti, Mo and W exhibit strong segregation tendency, while the elements with weak segregation tendency include Ni, Cr, Co and Al. There are fine MC carbides distributed in the interdendritic zone of the powder, the size is about 200nm. The particle size distribution of powders measured by laser diffraction and dynamic image analysis methods are similar. The D50 value of DZ4125 powder is 70.2μm and 72.8μm. The dynamic image analysis result shows that the DZ4125 alloy powders possess good sphericity, and the SPHT and b/l values are 0.91 and 0.86, respectively. The DZ4125 superalloy powders have good apparent density, tap density and flowablity. The apparent density and tap density of the alloy powders can reach 52% and 63% of the theoretical density of the DZ4125 alloy, respectively. In addition, the DZ4125 superalloy powders possess compressibility of 17.7% and flowability of 20.79 s?(50 g)-1.
2021, 50(11):3987-3994.
DOI: 10.12442/j.issn.1002-185X.20200860
Abstract:
The high entropy alloy coating was successfully prepared on the surface of 45# steel matrix by cold spray assisted in situ synthesis of FeCoxCrAlCu (x =0,0.5,1,1.5,2) high entropy alloy coating. The effects of Co content on phase structure, microstructure, hardness, wear resistance and corrosion resistance of alloy coating were analyzed by XRD,SEM,EDS,TEM, microhardness meter, abrasive wear testing machine, electrochemical workstation and so on. The results show that the alloy coating was composed of simple FCC+BCC two phase mixed structure, and the change of Co content has little influence on the amount of phase structure of the coating.With the increase of Co content, the number of dendrites in the microstructure of the alloy coating increased and got obvious coarsening.The number of crystals had increased, and it had been significantly coarsened. The microstructure was enriched with Fe, Cr, Co in the dendrites, and Cu was enriched between the dendrites, and Al was evenly distributed in the entire coating.With the increase of Co content, the hardness first increased and then decreased. When Co=1, the hardness of the alloy coating reached a maximum of 555.6HV.The minimum friction coefficient in the alloy coating is 0.361.In 3.5wt.%NaCl corrosive medium, the alloy coating had a positive self-corrosion potential compared with the 45# steel substrate (Ecorr=-0.325V), indicating that the coating had better corrosion resistance than the substrate.
The high entropy alloy coating was successfully prepared on the surface of 45# steel matrix by cold spray assisted in situ synthesis of FeCoxCrAlCu (x =0,0.5,1,1.5,2) high entropy alloy coating. The effects of Co content on phase structure, microstructure, hardness, wear resistance and corrosion resistance of alloy coating were analyzed by XRD,SEM,EDS,TEM, microhardness meter, abrasive wear testing machine, electrochemical workstation and so on. The results show that the alloy coating was composed of simple FCC+BCC two phase mixed structure, and the change of Co content has little influence on the amount of phase structure of the coating.With the increase of Co content, the number of dendrites in the microstructure of the alloy coating increased and got obvious coarsening.The number of crystals had increased, and it had been significantly coarsened. The microstructure was enriched with Fe, Cr, Co in the dendrites, and Cu was enriched between the dendrites, and Al was evenly distributed in the entire coating.With the increase of Co content, the hardness first increased and then decreased. When Co=1, the hardness of the alloy coating reached a maximum of 555.6HV.The minimum friction coefficient in the alloy coating is 0.361.In 3.5wt.%NaCl corrosive medium, the alloy coating had a positive self-corrosion potential compared with the 45# steel substrate (Ecorr=-0.325V), indicating that the coating had better corrosion resistance than the substrate.
2021, 50(11):3995-4003.
DOI: 10.12442/j.issn.1002-185X.20200866
Abstract:
The content of W, Mo, Co, Cr, Al, Ta and other elements in the single crystal superalloy was optimized through experimental data and thermodynamic calculations.A new third-generation single crystal superalloy WZ30 with Re content of 5 wt% was designed. In this paper, the metallographic and mechanical properties of WZ30 are studied and analyzed, and compared with existing second-generation and third-generation single crystal superalloys. The results show that WZ30 has uniform microstructure after heat treatment. The yield strengths of WZ30 are 938MPa, 639MPa and 436MPa at 760℃, 980℃ and 1100℃ respectively. When the temperature is higher than 1000℃, the tensile performance of WZ30 is better than that of the second-generation single crystal superalloy. The creep rupture life is 642h at 980°C/250MPa; the creep rupture life is 254h at 1100℃/137MPa, which is significantly better than that of the second-generation single crystal superalloys. The low cycle fatigue life of WZ30 is better than the second-generation single crystal superalloy DD6 at 980℃. WZ30 alloy has better oxidation resistance and structural stability in high temperature cyclic oxidation experiments.
The content of W, Mo, Co, Cr, Al, Ta and other elements in the single crystal superalloy was optimized through experimental data and thermodynamic calculations.A new third-generation single crystal superalloy WZ30 with Re content of 5 wt% was designed. In this paper, the metallographic and mechanical properties of WZ30 are studied and analyzed, and compared with existing second-generation and third-generation single crystal superalloys. The results show that WZ30 has uniform microstructure after heat treatment. The yield strengths of WZ30 are 938MPa, 639MPa and 436MPa at 760℃, 980℃ and 1100℃ respectively. When the temperature is higher than 1000℃, the tensile performance of WZ30 is better than that of the second-generation single crystal superalloy. The creep rupture life is 642h at 980°C/250MPa; the creep rupture life is 254h at 1100℃/137MPa, which is significantly better than that of the second-generation single crystal superalloys. The low cycle fatigue life of WZ30 is better than the second-generation single crystal superalloy DD6 at 980℃. WZ30 alloy has better oxidation resistance and structural stability in high temperature cyclic oxidation experiments.
2021, 50(11):4003-4009.
DOI: 10.12442/j.issn.1002-185X.20200859
Abstract:
In this paper, the effective connection between kovar alloy 4J29 and float glass was realized by using ALTSAB technology and SnAg3.5Ti2 solder. The effects of voltage and temperature on the interface microstructure and shear strength were studied, and the mechanism of bonding formation was explored. The results show that: with the increase of voltage and temperature, the interface between glass and solder has no significant change, new chemical bonds ≡Si-O-Ti and ≡Si-O-Sn are formed at the interface, and TiO and SnO are formed by oxidation reaction; there is reaction dissolution phenomenon between solder and alloy side, FeSn2 phase is formed at the kovar alloy side.There are some slender rod-shaped and needle-like Ni3Sn4 phases in the solder. It is considered that the formation of sodium ion depletion layer and the diffusion of Ti2+ and Sn2+ into the glass matrix are the key to the formation of effective bonding. The maximum shear strength is 12.5Mpa when the voltage is 1000V and the temperature is 400 ℃.
In this paper, the effective connection between kovar alloy 4J29 and float glass was realized by using ALTSAB technology and SnAg3.5Ti2 solder. The effects of voltage and temperature on the interface microstructure and shear strength were studied, and the mechanism of bonding formation was explored. The results show that: with the increase of voltage and temperature, the interface between glass and solder has no significant change, new chemical bonds ≡Si-O-Ti and ≡Si-O-Sn are formed at the interface, and TiO and SnO are formed by oxidation reaction; there is reaction dissolution phenomenon between solder and alloy side, FeSn2 phase is formed at the kovar alloy side.There are some slender rod-shaped and needle-like Ni3Sn4 phases in the solder. It is considered that the formation of sodium ion depletion layer and the diffusion of Ti2+ and Sn2+ into the glass matrix are the key to the formation of effective bonding. The maximum shear strength is 12.5Mpa when the voltage is 1000V and the temperature is 400 ℃.
2021, 50(11):4010-4014.
DOI: 10.12442/j.issn.1002-185X.20200867
Abstract:
Pure ZnO, Cu-ZnO, S-ZnO and (Cu,S) -ZnO nanoparticles were prepared by hydrothermal method. The crystal structure and surface morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties of electrodes were measured using an electrochemical workstation. Furthermore, the methylene blue solution was used to simulate wastewater to study its photoelectrochemical property. The results showed that the addition of dopant did not change the crystal structure, but the grain size decreased significantly, the surface area increased, and the surface distribution was more uniform. The electrocatalytic activity of the electrode is significantly increased after doping. Among them, (Cu,S)-ZnO nanoparticles has the best electrochemical properties and the highest degradation rate of methylene blue solution, up to 87.69%.
Pure ZnO, Cu-ZnO, S-ZnO and (Cu,S) -ZnO nanoparticles were prepared by hydrothermal method. The crystal structure and surface morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties of electrodes were measured using an electrochemical workstation. Furthermore, the methylene blue solution was used to simulate wastewater to study its photoelectrochemical property. The results showed that the addition of dopant did not change the crystal structure, but the grain size decreased significantly, the surface area increased, and the surface distribution was more uniform. The electrocatalytic activity of the electrode is significantly increased after doping. Among them, (Cu,S)-ZnO nanoparticles has the best electrochemical properties and the highest degradation rate of methylene blue solution, up to 87.69%.
2021, 50(11):4015-4022.
DOI: 10.12442/j.issn.1002-185X.20200872
Abstract:
The intermediate dense and surface porous Ti-13Nb-13Zr gradient alloy was fabricated by spark plasma sintering(SPS). The effect of sintering temperature (950~1200℃) on the microstructural evolution, interface bonding, surface porosity, mechanical properties and in vitro mineralization properties of gradient alloy were investigated. The results show that the a-Ti phase in the gradient alloy decreases,and the β-Ti phase increases with the gradual increase of the sintering temperature, then the structure is gradually continuous and uniformly distributed, the grains are refined, and the interface between the intermediate matrix and the porous layer is continuously transitioned well formed with metallurgical bonding.The porosity of the surface porous layer decreases and the average pore diameter decreases.The compressive strength value of the gradient alloy firstly increases and then decreases with the increase of the sintering temperature, while the compressive elastic modulus value slightly changes.Based on the above analysis, it shows that at the 1150℃ sintering temperature, the fabricated surface porous gradient alloy not only has good mechanical properties (compressive strength 893MPa, compressive elastic modulus 16GPa), but also has suitable pore parameters (porosity 34.7%, average pore diameter 340.9um) and excellent bone-like apatite forming ability together with in vitro mineralization performance.
The intermediate dense and surface porous Ti-13Nb-13Zr gradient alloy was fabricated by spark plasma sintering(SPS). The effect of sintering temperature (950~1200℃) on the microstructural evolution, interface bonding, surface porosity, mechanical properties and in vitro mineralization properties of gradient alloy were investigated. The results show that the a-Ti phase in the gradient alloy decreases,and the β-Ti phase increases with the gradual increase of the sintering temperature, then the structure is gradually continuous and uniformly distributed, the grains are refined, and the interface between the intermediate matrix and the porous layer is continuously transitioned well formed with metallurgical bonding.The porosity of the surface porous layer decreases and the average pore diameter decreases.The compressive strength value of the gradient alloy firstly increases and then decreases with the increase of the sintering temperature, while the compressive elastic modulus value slightly changes.Based on the above analysis, it shows that at the 1150℃ sintering temperature, the fabricated surface porous gradient alloy not only has good mechanical properties (compressive strength 893MPa, compressive elastic modulus 16GPa), but also has suitable pore parameters (porosity 34.7%, average pore diameter 340.9um) and excellent bone-like apatite forming ability together with in vitro mineralization performance.
2021, 50(11):4023-4030.
DOI: 10.12442/j.issn.1002-185X.20200877
Abstract:
The C/C-SiC composites were prepared by chemical vapor infiltration (CVI) combined with polymer infiltration carbonization (PIC) and reactive melt infiltration (RMI) using pierced non-woven carbon fiber felt preform. The microstructure and ablation properties were investigated. The results presented that non-woven carbon fiber cloth and pierced carbon fiber bundle formed dense C/C microstructure after CVI and PIC processes. SiC matrix was mainly located in the felt after RMI process and the content was 37.3wt%. SiC-rich layer was formed on the surface of the composites. When the ablation distance is 20mm, the ablation rates on XY and Z directions of the composites are 0.8×10-4 mm/s and 3.6×10-4 mm/s, respectively. The excellent ablation performance could be owing to the passive oxidation of SiC-rich layer on the surface. With the ablation distance decreased from 20mm to 10mm, the ablation rate of the composites changed slowly and then increased rapidly, because of the active oxidation ablation of the composites.
The C/C-SiC composites were prepared by chemical vapor infiltration (CVI) combined with polymer infiltration carbonization (PIC) and reactive melt infiltration (RMI) using pierced non-woven carbon fiber felt preform. The microstructure and ablation properties were investigated. The results presented that non-woven carbon fiber cloth and pierced carbon fiber bundle formed dense C/C microstructure after CVI and PIC processes. SiC matrix was mainly located in the felt after RMI process and the content was 37.3wt%. SiC-rich layer was formed on the surface of the composites. When the ablation distance is 20mm, the ablation rates on XY and Z directions of the composites are 0.8×10-4 mm/s and 3.6×10-4 mm/s, respectively. The excellent ablation performance could be owing to the passive oxidation of SiC-rich layer on the surface. With the ablation distance decreased from 20mm to 10mm, the ablation rate of the composites changed slowly and then increased rapidly, because of the active oxidation ablation of the composites.
2021, 50(11):4031-4036.
DOI: 10.12442/j.issn.1002-185X.20200883
Abstract:
AlCrCuFeNbxNiTi (x = 0, 0.25, 0.5, 1.0) high-entropy alloys were prepared by arc melting, and the effect of different Nb content on the microstructures and mechanical properties of AlCrCuFeNbxNiTi high-entropy alloys was studied. The results show that the phase of AlCrCuFeNbxNiTi (x = 0, 0.25, 0.5, 1.0) high-entropy alloys consists of ordered FCC L21 phase and Laves phase, together with minor BCC(A2) and FCC phases. The addition of Nb element can promote the formation of Laves phase and has a certain inhibitory effect on the segregation of Cu elements; The phase formation criterion suitable for AlCrCuFeNbxNiTi high-entropy alloys is found through the calculation of phase criterion parameters; the addition of an appropriate amount of Nb can improve the mechanical properties of AlCrCuFeNiTi six-element high-entropy alloy; AlCrCuFeNb0.5NiTi high-entropy alloy has better comprehensive mechanical properties. The compressive strength reaches 1587.4 MPa, and the hardness reaches 568.8 HV. When the Nb element content is too high, too much Laves phase will be formed and the alloy will exhibit premature embrittlement.
AlCrCuFeNbxNiTi (x = 0, 0.25, 0.5, 1.0) high-entropy alloys were prepared by arc melting, and the effect of different Nb content on the microstructures and mechanical properties of AlCrCuFeNbxNiTi high-entropy alloys was studied. The results show that the phase of AlCrCuFeNbxNiTi (x = 0, 0.25, 0.5, 1.0) high-entropy alloys consists of ordered FCC L21 phase and Laves phase, together with minor BCC(A2) and FCC phases. The addition of Nb element can promote the formation of Laves phase and has a certain inhibitory effect on the segregation of Cu elements; The phase formation criterion suitable for AlCrCuFeNbxNiTi high-entropy alloys is found through the calculation of phase criterion parameters; the addition of an appropriate amount of Nb can improve the mechanical properties of AlCrCuFeNiTi six-element high-entropy alloy; AlCrCuFeNb0.5NiTi high-entropy alloy has better comprehensive mechanical properties. The compressive strength reaches 1587.4 MPa, and the hardness reaches 568.8 HV. When the Nb element content is too high, too much Laves phase will be formed and the alloy will exhibit premature embrittlement.
2021, 50(11):4037-4044.
DOI: 10.12442/j.issn.1002-185X.20200884
Abstract:
Corn stalk core (CSC) is low-cost and sustainable biomaterials, which can be used as a filtration material due to its naturally porous structure. A simple method of chemical precipitation was applied to load ZnO nanoparticles (ZnO NPs) into the core, which was used for water purification and sterilization. The different zinc sources had an obvious effect on various morphology and chemical characteristics of ZnO immobilized in CSC, leading to a variety of antibacterial activities. The composite biofilter prepared from zinc acetate showed the excellent antibacterial effect, and the antibacterial rates of Escherichia coli and Staphylococcus aureus reached 94.5% and 90.5% respectively, after filtration for 5 min. The antibacterial mechanism of the hybrid column might be ascribed to the interception of bacteria by hierarchical porous structure of CSC, resulting in an increase of the physical friction with nanoparticles and chemical reactions with reactive oxygen species (ROS) and hydrated zinc ions. Consequently, the cell membranes of bacteria were damaged and the components in cells were leaked, finally leading to the death of bacteria.
Corn stalk core (CSC) is low-cost and sustainable biomaterials, which can be used as a filtration material due to its naturally porous structure. A simple method of chemical precipitation was applied to load ZnO nanoparticles (ZnO NPs) into the core, which was used for water purification and sterilization. The different zinc sources had an obvious effect on various morphology and chemical characteristics of ZnO immobilized in CSC, leading to a variety of antibacterial activities. The composite biofilter prepared from zinc acetate showed the excellent antibacterial effect, and the antibacterial rates of Escherichia coli and Staphylococcus aureus reached 94.5% and 90.5% respectively, after filtration for 5 min. The antibacterial mechanism of the hybrid column might be ascribed to the interception of bacteria by hierarchical porous structure of CSC, resulting in an increase of the physical friction with nanoparticles and chemical reactions with reactive oxygen species (ROS) and hydrated zinc ions. Consequently, the cell membranes of bacteria were damaged and the components in cells were leaked, finally leading to the death of bacteria.
2021, 50(11):4045-4050.
DOI: 10.12442/j.issn.1002-185X.20200887
Abstract:
Supercapacitors have the characteristics of high specific capacitance, long cycle life and green pollution-free, and their excellent electrochemical performance has attracted much attention. In this paper, NiMoO4/g-C3N4 composite powder was hydrothermally synthesized, and the composite powder was coated on foamed nickel to prepare NiMoO4/g-C3N4 electrode material. The results show that the morphology of NiMoO4/g-C3N4 powder is mainly NiMoO4 nanorods and g-C3N4 clumps, and NiMoO4 nanorods are grown on g-C3N4 nanosheets.The electrochemical performance test results show that adding 30at% g-C3N4 to NiMoO4 can reduce the equivalent series resistance and diffusion impedance of the capacitor system, which is beneficial to the oxidation-reduction reaction. Compared with other electrode materials with g-C3N4 content, NiMoO4/g-C3N4 electrode materials with a g-C3N4 content of 30at% have higher specific capacitance (584.3F/g) and better rate characteristics.
Supercapacitors have the characteristics of high specific capacitance, long cycle life and green pollution-free, and their excellent electrochemical performance has attracted much attention. In this paper, NiMoO4/g-C3N4 composite powder was hydrothermally synthesized, and the composite powder was coated on foamed nickel to prepare NiMoO4/g-C3N4 electrode material. The results show that the morphology of NiMoO4/g-C3N4 powder is mainly NiMoO4 nanorods and g-C3N4 clumps, and NiMoO4 nanorods are grown on g-C3N4 nanosheets.The electrochemical performance test results show that adding 30at% g-C3N4 to NiMoO4 can reduce the equivalent series resistance and diffusion impedance of the capacitor system, which is beneficial to the oxidation-reduction reaction. Compared with other electrode materials with g-C3N4 content, NiMoO4/g-C3N4 electrode materials with a g-C3N4 content of 30at% have higher specific capacitance (584.3F/g) and better rate characteristics.
2021, 50(11):4051-4058.
DOI: 10.12442/j.issn.1002-185X.20200889
Abstract:
This paper mainly studied the change rule of aging treatment temperature and aging holding time on the structure and performance of 7075 aluminum alloy laser weld. Scanning Electron Microscopy (SEM) was used to observe the chain T phase formed during welding. With the extension of heat preservation time, the T phase melted into the substrate gradually. After aging treatment temperature 120 ℃ at 24 h,the T phasewas uniformly distributed in a spherical shape, which reduced its cleavage effect on the matrix. TEM and SADE image showed that the nanoscaleη" phase was precipitated on the crystal axis of [011]Al、[12]Al、[001]Al. With the extension of time, the size and distribution density of η" changed and gradually becameη. The phase prevented dislocation movement to improve the mechanical properties of welds. By comparing the microhardness and tensile strength, 7075 aluminum alloy laser welded joint has the best mechanical properties by aging treatment temperature 120 ℃ at 24 h.
This paper mainly studied the change rule of aging treatment temperature and aging holding time on the structure and performance of 7075 aluminum alloy laser weld. Scanning Electron Microscopy (SEM) was used to observe the chain T phase formed during welding. With the extension of heat preservation time, the T phase melted into the substrate gradually. After aging treatment temperature 120 ℃ at 24 h,the T phasewas uniformly distributed in a spherical shape, which reduced its cleavage effect on the matrix. TEM and SADE image showed that the nanoscaleη" phase was precipitated on the crystal axis of [011]Al、[12]Al、[001]Al. With the extension of time, the size and distribution density of η" changed and gradually becameη. The phase prevented dislocation movement to improve the mechanical properties of welds. By comparing the microhardness and tensile strength, 7075 aluminum alloy laser welded joint has the best mechanical properties by aging treatment temperature 120 ℃ at 24 h.
2021, 50(11):4059.
DOI: 10.12442/j.issn.1002-185X.20200882
Abstract:
The plating materials of arc ion plating leaved target by melt splash. It is easy to cause secondary tempering of the matrix because of micron sized particles on the coating surface. The ionization rateofmagnetron sputtering is low due to the leave-target mode of cascade collision. The deposition rate of high power pulsed magnetron sputtering is low due to the small duty cycle of pulse discharge. These defects seriously restrict the wide application of current mainstream coating deposition technology.Based on the physical knowledge of gas discharge plasma, a new type of stepped dual-stage pulsed electric field was used to initiate gas micro arc discharge between cathode target and anode chamber. With the help of the high density plasma produced by micro arc discharge, the kinetic energy of argon ion bombardment on the target surface and the Joule heat generated by the target surface are enhanced. The collision enhanced thermal emission of the plating material can be realized, and the ionization rate is increased, which provides the possibility for improving and regulating the coating structure. The results showed that the gas micro arc discharge induced by dual-stage pulsed electric field presents dazzling blue and white light. The surface morphology of the target surface after discharge showed the morphology of meteorite crater and water flow crater. The target surface morphology was not exactly the same as the undulating crater left after the collision sputtering of the plating material under DC electric field. The the plating material leaved target by collision sputtering and thermal emission. At the same time, the TiN coating prepared by the dual-stage pulsed electric field had a relatively compact structure, and the deposition rate reached 51 nm/min, which is significantly improved compared with the traditional high power pulsed magnetron sputtering.
The plating materials of arc ion plating leaved target by melt splash. It is easy to cause secondary tempering of the matrix because of micron sized particles on the coating surface. The ionization rateofmagnetron sputtering is low due to the leave-target mode of cascade collision. The deposition rate of high power pulsed magnetron sputtering is low due to the small duty cycle of pulse discharge. These defects seriously restrict the wide application of current mainstream coating deposition technology.Based on the physical knowledge of gas discharge plasma, a new type of stepped dual-stage pulsed electric field was used to initiate gas micro arc discharge between cathode target and anode chamber. With the help of the high density plasma produced by micro arc discharge, the kinetic energy of argon ion bombardment on the target surface and the Joule heat generated by the target surface are enhanced. The collision enhanced thermal emission of the plating material can be realized, and the ionization rate is increased, which provides the possibility for improving and regulating the coating structure. The results showed that the gas micro arc discharge induced by dual-stage pulsed electric field presents dazzling blue and white light. The surface morphology of the target surface after discharge showed the morphology of meteorite crater and water flow crater. The target surface morphology was not exactly the same as the undulating crater left after the collision sputtering of the plating material under DC electric field. The the plating material leaved target by collision sputtering and thermal emission. At the same time, the TiN coating prepared by the dual-stage pulsed electric field had a relatively compact structure, and the deposition rate reached 51 nm/min, which is significantly improved compared with the traditional high power pulsed magnetron sputtering.
2021, 50(11):4066-4072.
DOI: 10.12442/j.issn.1002-185X.20200910
Abstract:
Three dimensional continuous network Ti2AlC / TiAl Composites were prepared by vacuum hot pressing. The high temperature oxidation behavior and mechanism of the composites were studied by friction and wear tester. The results show that under the high temperature oxidation condition, the surface of the composite is formed with Al2O3 mossy oxide below 600 ℃, and the TiO2 agglomerate and the mixed layer of TiO2 and Al2O3 are formed at 800 ℃; with the increase of temperature, the friction coefficient decreases to 0.3237 due to the lubrication of the oxide film, and the softening of the substrate and the prominent growth of TiO2 agglomerates make the wear rate increase to 4.5×10-4mm3/(N.m) The abrasive wear is transformed into the mixed wear of abrasive wear and oxidation wear.
Three dimensional continuous network Ti2AlC / TiAl Composites were prepared by vacuum hot pressing. The high temperature oxidation behavior and mechanism of the composites were studied by friction and wear tester. The results show that under the high temperature oxidation condition, the surface of the composite is formed with Al2O3 mossy oxide below 600 ℃, and the TiO2 agglomerate and the mixed layer of TiO2 and Al2O3 are formed at 800 ℃; with the increase of temperature, the friction coefficient decreases to 0.3237 due to the lubrication of the oxide film, and the softening of the substrate and the prominent growth of TiO2 agglomerates make the wear rate increase to 4.5×10-4mm3/(N.m) The abrasive wear is transformed into the mixed wear of abrasive wear and oxidation wear.
2021, 50(11):4073-4078.
DOI: 10.12442/j.issn.1002-185X.20200893
Abstract:
The pure tungsten metal prepared by chemical vapor deposition (CVD) have distinct grain size on different surfaces. The high temperature oxidation experiment was carried out in dry air and at 800℃. The effect of grain size on CVD tungsten was studied from the growth curve, phase composition and microstructure of the oxide film. The results show that the fine grain tungsten can form oxide film more quickly during the oxidation process, promote the formation of continuous and compact oxide film, and improve the oxidation resistance of tungsten. The effect of grain size on the oxidation behavior of tungsten is positive. As the tungsten in the fine grain part oxidizes to the interior, the grain size of the surface and the top surface are the same, and the oxidation rate of the bottom and top surface tend to be the same. In addition, the oxidation rate of the deposition layer increases obviously due to the influence of the edge effect.
The pure tungsten metal prepared by chemical vapor deposition (CVD) have distinct grain size on different surfaces. The high temperature oxidation experiment was carried out in dry air and at 800℃. The effect of grain size on CVD tungsten was studied from the growth curve, phase composition and microstructure of the oxide film. The results show that the fine grain tungsten can form oxide film more quickly during the oxidation process, promote the formation of continuous and compact oxide film, and improve the oxidation resistance of tungsten. The effect of grain size on the oxidation behavior of tungsten is positive. As the tungsten in the fine grain part oxidizes to the interior, the grain size of the surface and the top surface are the same, and the oxidation rate of the bottom and top surface tend to be the same. In addition, the oxidation rate of the deposition layer increases obviously due to the influence of the edge effect.
2021, 50(11):4079-4088.
DOI: 10.12442/j.issn.1002-185X.20200900
Abstract:
This study investigated the precipitated phases of Titanium-stabilized 15Cr-15Ni austenitic stainless steel with different niobium contents (0-0.46 wt.%), in which the types, morphology and distribution of precipitated phases after solution treatment and aging treatment were characterized by means of OM, SEM, and TEM. Results show that Ti and Mo can be partly replaced with Nb in (Ti,Mo)C phase to form a Nb-rich (Nb,Ti)C phase in 0.21wt.%Nb and 0.46wt.%Nb alloys. What’s more , the increase of Nb content refines austenite matrix structure after solution treatment. In addition , the main phases in the alloy after aging at 850℃ for 1000h are sigma and MC carbides .the increase of Nb content not only promotes to enrich Nb and Mo elements in the sigma phases, but also furthers it to be finer and dispersed. Besides, in the range of 0-0.46wt.%Nb, the tensile results of solution and aged specimens at room temperature and 650℃ show that the increase of Nb content has little effect on the tensile properties of the solution alloy at room temperature and high temperature, while the sigma promoted by Nb has no effect on the tensile properties of the aged alloy.
This study investigated the precipitated phases of Titanium-stabilized 15Cr-15Ni austenitic stainless steel with different niobium contents (0-0.46 wt.%), in which the types, morphology and distribution of precipitated phases after solution treatment and aging treatment were characterized by means of OM, SEM, and TEM. Results show that Ti and Mo can be partly replaced with Nb in (Ti,Mo)C phase to form a Nb-rich (Nb,Ti)C phase in 0.21wt.%Nb and 0.46wt.%Nb alloys. What’s more , the increase of Nb content refines austenite matrix structure after solution treatment. In addition , the main phases in the alloy after aging at 850℃ for 1000h are sigma and MC carbides .the increase of Nb content not only promotes to enrich Nb and Mo elements in the sigma phases, but also furthers it to be finer and dispersed. Besides, in the range of 0-0.46wt.%Nb, the tensile results of solution and aged specimens at room temperature and 650℃ show that the increase of Nb content has little effect on the tensile properties of the solution alloy at room temperature and high temperature, while the sigma promoted by Nb has no effect on the tensile properties of the aged alloy.
Geng Xiang
,
Luo Guangnan
,
Wang Wanjing
,
Li Qiang
,
Wang Jichao
,
Xie Chunyi
,
Huang Lingming
,
Chen Zheng
,
Peng Wuqingliang
2021, 50(11):4089-4094.
DOI: 10.12442/j.issn.1002-185X.20200902
Abstract:
For performance evaluation of tungsten materials in fusion device, four-point bending test (4PBT) was carried out to analyse the ductile-brittle transition temperature (DBTT) of tungsten material. DBTT of industrial rolling pure tungsten measured by standard four-point bending method is under 150 ℃, basing on analysis to the change of strain rate and strength with temperature. This result is lower than the measured value of the tensile test and impact test. Then the results of 4PBT with different loading rates and tensile test were compared to confirm the loading rate dependence of DBTTs obtained by different test methods. Finally, the reasons for the influence of test methods on DBTT measurement were analyzed and discussed.
For performance evaluation of tungsten materials in fusion device, four-point bending test (4PBT) was carried out to analyse the ductile-brittle transition temperature (DBTT) of tungsten material. DBTT of industrial rolling pure tungsten measured by standard four-point bending method is under 150 ℃, basing on analysis to the change of strain rate and strength with temperature. This result is lower than the measured value of the tensile test and impact test. Then the results of 4PBT with different loading rates and tensile test were compared to confirm the loading rate dependence of DBTTs obtained by different test methods. Finally, the reasons for the influence of test methods on DBTT measurement were analyzed and discussed.
2021, 50(11):4095-4102.
DOI: 10.12442/j.issn.1002-185X.20200905
Abstract:
Creep age-forming combined creep and precipitation strengthening on aluminum alloy is an advanced integrated panel forming technology in the aerospace industry, and has been widely studied. The interaction between precipitation and dislocation creep in7xxx series aluminum alloy significantly affect on stress relaxation behavior, which decides the forming quality and properties of integrated panel, during age-forming process, since 7xxx series aluminum alloy as a typical age-hardening alloys. In this paper, the effect of different size precipitates on stress relaxation behavior of 7050 aluminum alloy during age-forming process has been investigated, which is helpful to apply creep age-forming technology of 7xxx series aluminum alloy with different tempers. The precipitates can obstruct dislocation thermal activation, therefore 7050 aluminum alloy with different size precipitates obviously exhibits different stress relaxation behavior, and relaxation rate decreases and relaxation limit increases with increasing precipitates size respectively. The calculation of dislocation activation volume and microstructure characterization proves that the obstruction to dislocation motion from precipitates improves with increasing precipitates size. Besides, a special threshold stress phenomena was present in the stress relaxation of the age-forming process, which was scribed to the interaction between precipitation and dislocation in 7050 aluminum alloy.
Creep age-forming combined creep and precipitation strengthening on aluminum alloy is an advanced integrated panel forming technology in the aerospace industry, and has been widely studied. The interaction between precipitation and dislocation creep in7xxx series aluminum alloy significantly affect on stress relaxation behavior, which decides the forming quality and properties of integrated panel, during age-forming process, since 7xxx series aluminum alloy as a typical age-hardening alloys. In this paper, the effect of different size precipitates on stress relaxation behavior of 7050 aluminum alloy during age-forming process has been investigated, which is helpful to apply creep age-forming technology of 7xxx series aluminum alloy with different tempers. The precipitates can obstruct dislocation thermal activation, therefore 7050 aluminum alloy with different size precipitates obviously exhibits different stress relaxation behavior, and relaxation rate decreases and relaxation limit increases with increasing precipitates size respectively. The calculation of dislocation activation volume and microstructure characterization proves that the obstruction to dislocation motion from precipitates improves with increasing precipitates size. Besides, a special threshold stress phenomena was present in the stress relaxation of the age-forming process, which was scribed to the interaction between precipitation and dislocation in 7050 aluminum alloy.
2021, 50(11):4103-4112.
DOI: 10.12442/j.issn.1002-185X.20200908
Abstract:
Egg-box structure is a new type of periodic single cell lightweight structure, which has the characteristics of low density, high specific strength and high energy absorption capacity.Was established based on finite element method in this paper, surface with a plane egg box type sandwich board egg carton drop hammer impact model of sandwich panels, a comparative analysis of its impact resistant properties, and the different egg box type structure under the condition of dynamic compression mechanical properties were analyzed, the results show that the impact of sandwich board goes through three stages, including the compression stage as the main stage of energy absorption, through the impact kinetic energy is transformed into the sandwich board plastic dissipation can to achieve the goal of buffer energy absorption.At the same time, these characteristics depend on the forming height and the thickness of upper and lower panels and other structural parameters. When the forming height of single-cell structure is 6mm,the period of single cell is 20mm ,the thickness of upper and lower panels is 0.5mm, and the radius of curvature is 400mm, the composite egg-box sandwich panel has better mechanical properties.
Egg-box structure is a new type of periodic single cell lightweight structure, which has the characteristics of low density, high specific strength and high energy absorption capacity.Was established based on finite element method in this paper, surface with a plane egg box type sandwich board egg carton drop hammer impact model of sandwich panels, a comparative analysis of its impact resistant properties, and the different egg box type structure under the condition of dynamic compression mechanical properties were analyzed, the results show that the impact of sandwich board goes through three stages, including the compression stage as the main stage of energy absorption, through the impact kinetic energy is transformed into the sandwich board plastic dissipation can to achieve the goal of buffer energy absorption.At the same time, these characteristics depend on the forming height and the thickness of upper and lower panels and other structural parameters. When the forming height of single-cell structure is 6mm,the period of single cell is 20mm ,the thickness of upper and lower panels is 0.5mm, and the radius of curvature is 400mm, the composite egg-box sandwich panel has better mechanical properties.
2021, 50(11):4113-4118.
DOI: 10.12442/j.issn.1002-185X.20200918
Abstract:
Ti/ZrCo/Ti, ZrCo/Ti/ZrCo/Ti multilayer composite films are successfully prepared by magnetron sputtering.The micro-structure and hydrogen storage performance of multilayer composite films are studied,The application possibility of the composite membrane as the tritium target of the deuterium tritium neutron generator is discussed in detail.Experiments show that the prepared multilayer composite film is composed of ZrCo phase and Ti phase, and the interface between the layers is clearly distinguishable. Compared with the ZrCo film, the introduction of the Ti film layer significantly increases the hydrogen absorption of the composite film and retains the stability of the film hydride. At the same time, the disproportionation reaction of ZrCo is significantly suppressed.The alternating composite film of ZrCo layer and Ti layer constructed in this study has high hydrogen absorption capacity and high thermal stability, which extends the application field of ZrCo alloy and provides an important reference for the design and development of new tritium target materials of composite film.
Ti/ZrCo/Ti, ZrCo/Ti/ZrCo/Ti multilayer composite films are successfully prepared by magnetron sputtering.The micro-structure and hydrogen storage performance of multilayer composite films are studied,The application possibility of the composite membrane as the tritium target of the deuterium tritium neutron generator is discussed in detail.Experiments show that the prepared multilayer composite film is composed of ZrCo phase and Ti phase, and the interface between the layers is clearly distinguishable. Compared with the ZrCo film, the introduction of the Ti film layer significantly increases the hydrogen absorption of the composite film and retains the stability of the film hydride. At the same time, the disproportionation reaction of ZrCo is significantly suppressed.The alternating composite film of ZrCo layer and Ti layer constructed in this study has high hydrogen absorption capacity and high thermal stability, which extends the application field of ZrCo alloy and provides an important reference for the design and development of new tritium target materials of composite film.
42 Effect of Annealing Temperature on Microstructure and Properties of Thixo-Extruded Tin Bronze Bush
2021, 50(11):4119-4127.
DOI: 10.12442/j.issn.1002-185X.20200914
Abstract:
The thixo-extruded tin bronze bushing parts have been used for annealing treatment, and the effect of annealing temperature on the microstructure, element distribution, wear properties and mechanical properties of the thixo-extruded tin bronze bushing parts is studied. The result shows that after annealing treatment, Sn and P elements can diffuse from the liquid phase to the Cu matrix solid phase forming α-Cu solid solution. As the annealing temperature increases, the average grain size gradually increases, and the shape factor first decreases and then increases, Brinell hardness first increases and then decreases, wear rate and friction coefficient first increase and then decrease, tensile strength and elongation first increase and then decrease. The microstructure and comprehensive properties of the tin bronze bushing are the best, when annealing at 500 ℃ for 120 min. The shape factor is 1.26, the average grain size is 75.2 μm, the tensile strength is 423 MPa, and the elongation is 6.6%. The Brinell hardness is 141 HBW, the wear rate is 6%, and the friction coefficient is 0.48.
The thixo-extruded tin bronze bushing parts have been used for annealing treatment, and the effect of annealing temperature on the microstructure, element distribution, wear properties and mechanical properties of the thixo-extruded tin bronze bushing parts is studied. The result shows that after annealing treatment, Sn and P elements can diffuse from the liquid phase to the Cu matrix solid phase forming α-Cu solid solution. As the annealing temperature increases, the average grain size gradually increases, and the shape factor first decreases and then increases, Brinell hardness first increases and then decreases, wear rate and friction coefficient first increase and then decrease, tensile strength and elongation first increase and then decrease. The microstructure and comprehensive properties of the tin bronze bushing are the best, when annealing at 500 ℃ for 120 min. The shape factor is 1.26, the average grain size is 75.2 μm, the tensile strength is 423 MPa, and the elongation is 6.6%. The Brinell hardness is 141 HBW, the wear rate is 6%, and the friction coefficient is 0.48.
2021, 50(11):4128-4134.
DOI: 10.12442/j.issn.1002-185X.20200934
Abstract:
The Ti45Zr35Cu5Ni15 bulk metallic glass with a small amount of nanocrystalline was prepared by copper mould injection casting. The dynamic compression properties of the alloy was investigated with the split Hopkinson pressure bar (SHPB) under high strain rates at room temperature (25℃) ,-80℃ and liquid nitrogen temperature (–196 ℃), respectively. The morphology characteristics of the compression fracture were observed by field emission scanning electron microscope (SEM) with energy spectrum. Comparative analysis shows that the material exhibited maximum dynamic compressive strength and plastic deformation at -80℃, and the maximum compressive strength reached 2378MPa when the plastic strain reached 12% , which exhibited excellent mechanical strength and toughness. Furthermore , uncommon profuse wrinkles were also found on the fracture surface. The mechanical properties of the materials were similar at room temperature and liquid nitrogen temperature. The maximum compressive strength was around 1600MPa while the plastic strain reached about 8%, and the river pattern on the fracture surface of the material could also be observed. In addition , the material showed strain softening at room temperature and strain rate strengthening at low temperature to a certain extent.
The Ti45Zr35Cu5Ni15 bulk metallic glass with a small amount of nanocrystalline was prepared by copper mould injection casting. The dynamic compression properties of the alloy was investigated with the split Hopkinson pressure bar (SHPB) under high strain rates at room temperature (25℃) ,-80℃ and liquid nitrogen temperature (–196 ℃), respectively. The morphology characteristics of the compression fracture were observed by field emission scanning electron microscope (SEM) with energy spectrum. Comparative analysis shows that the material exhibited maximum dynamic compressive strength and plastic deformation at -80℃, and the maximum compressive strength reached 2378MPa when the plastic strain reached 12% , which exhibited excellent mechanical strength and toughness. Furthermore , uncommon profuse wrinkles were also found on the fracture surface. The mechanical properties of the materials were similar at room temperature and liquid nitrogen temperature. The maximum compressive strength was around 1600MPa while the plastic strain reached about 8%, and the river pattern on the fracture surface of the material could also be observed. In addition , the material showed strain softening at room temperature and strain rate strengthening at low temperature to a certain extent.
Zhang Jinyong
,
Wu Yijin
,
Zhao Congcong
,
Chen Changjiu
,
Zhang Ping
,
Chen Zheng
,
Shen Baolong
,
A. Inoue
2021, 50(11):4135-4140.
DOI: 10.12442/j.issn.1002-185X.20200927
Abstract:
In this paper, the (Fe0.25Co0.25Ni0.25Cr0.125Mn0.125)100-xBx (x=8-16, at.%) alloys were prepared by vacuum arc melting, ejection casting into a copper mold and single-roller melt-spinning. The phase composition, microstructure evolution and mechanical properties of the high entropy alloys with different B content were studied under different casting conditions. The results show that the high entropy alloys can be transformed from fcc phase to amorphous phase by controlling B content and cooling rate. In the same casting process, the grains can be refined by adding B content, so that the strength and hardness of the alloys increase with the increase of B content.
In this paper, the (Fe0.25Co0.25Ni0.25Cr0.125Mn0.125)100-xBx (x=8-16, at.%) alloys were prepared by vacuum arc melting, ejection casting into a copper mold and single-roller melt-spinning. The phase composition, microstructure evolution and mechanical properties of the high entropy alloys with different B content were studied under different casting conditions. The results show that the high entropy alloys can be transformed from fcc phase to amorphous phase by controlling B content and cooling rate. In the same casting process, the grains can be refined by adding B content, so that the strength and hardness of the alloys increase with the increase of B content.
2021, 50(11):4141-4148.
DOI: 10.12442/j.issn.1002-185X.20200929
Abstract:
In this paper, a CrMn0.3FeVCu0.06 high entropy alloy was prepared by powder metallurgy technology. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to characterize the phase formation and microstructure of the milled powders and sintered bulk CrMn0.3FeVCu0.06 HEA. It was found that the sintered bulk CrMn0.3FeVCu0.06 high-entropy alloy exhibits a dual-phase structure of BCC structured matrix and FCC particles. The bulk CrMnFeVTi HEA exhibits high values of compressive strength and ductility due to grain boundary strengthening and precipitate strengthening. In addition, effects of fluence and temperature on surface morphology and mechanical properties of the CrMn0.3FeVCu0.06 alloy, irradiated by low energy high flux deuterium(D) plasma beams, were systematically investigated. When irradiation conditions were set as 500 K, 40 eV and 1×1022 m-2s-1, the critical fluence for blistering in the CrMn0.3FeVCu0.06 alloy is higher than 2.0×1025 m-2, which is much larger than the critical fluence in polycrystalline tungsten with similar irradiation conditions. It can been seen that the CrMn0.3FeVCu0.06 alloy has better irradiation resistance than polycrystalline tungsten in terms of D retention or inhibiting blister formation. The hardness of the alloy gradually increases with the increase of deuterium fluence, but decreases with increasing irradiation temperature. Due to severe lattice-distortion and sluggish diffusion effects HEA, the irradiation hardening in CrMn0.3FeVCu0.06 HEA is more sensitive to the change of irradiation temperature.
In this paper, a CrMn0.3FeVCu0.06 high entropy alloy was prepared by powder metallurgy technology. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to characterize the phase formation and microstructure of the milled powders and sintered bulk CrMn0.3FeVCu0.06 HEA. It was found that the sintered bulk CrMn0.3FeVCu0.06 high-entropy alloy exhibits a dual-phase structure of BCC structured matrix and FCC particles. The bulk CrMnFeVTi HEA exhibits high values of compressive strength and ductility due to grain boundary strengthening and precipitate strengthening. In addition, effects of fluence and temperature on surface morphology and mechanical properties of the CrMn0.3FeVCu0.06 alloy, irradiated by low energy high flux deuterium(D) plasma beams, were systematically investigated. When irradiation conditions were set as 500 K, 40 eV and 1×1022 m-2s-1, the critical fluence for blistering in the CrMn0.3FeVCu0.06 alloy is higher than 2.0×1025 m-2, which is much larger than the critical fluence in polycrystalline tungsten with similar irradiation conditions. It can been seen that the CrMn0.3FeVCu0.06 alloy has better irradiation resistance than polycrystalline tungsten in terms of D retention or inhibiting blister formation. The hardness of the alloy gradually increases with the increase of deuterium fluence, but decreases with increasing irradiation temperature. Due to severe lattice-distortion and sluggish diffusion effects HEA, the irradiation hardening in CrMn0.3FeVCu0.06 HEA is more sensitive to the change of irradiation temperature.
Tan Zhilong
,
Ying Changchang
,
Wen Ming
,
Guo Junmei
,
Chen Jialin
,
Wang Chuanjun
,
Song Zhihao
,
Xu Yanting
2021, 50(11):4149-4156.
DOI: 10.12442/j.issn.1002-185X.20200933
Abstract:
Isothermal compression tests of NiPt15 alloys at temperatures ranging from 950 to 1150℃ and strain rates from 0.01 to 3s-1 were performed on Gleeble-3500 thermo-simulation machine. Based on stress-strain relationship curve of NiPt15 and hot processing maps during the hot deformation process were established. The power dissipation situation of NiPt15 alloy at different stage were analyzed. The damage instability mechanism of NiPt15 alloy was elucidated. According to the dynamic material model presented by Prasad, hot processing maps for hot working condition were established based on the effect of power dissipation and instability coefficient associated with various kinds of temperatures and stain rates. The results showed that the deformation temperature is the main factor affection of the curve variation trend and dynamic recrystallization. Moreover, the higher of deformation temperature and the lower of deformation rate, the dynamic recrystallization will be the more sufficient. Subsequently, the instability mechanism of NiPt15 alloy in thermal processing mainly included local plastic deformation, shear deformation zone and cracking. With the increase of true strain, local plastic deformation occured firstly, then shear deformation zone replaced it, and finally it evolved into cracking. The excellent safe processing zone for NiPt15 alloy were mainly concentrated in the non-instability zone . That was to say, the deformation parameters were within the range of 1000~1100℃, 0.03~0.1s-1 and 1100~1130℃, 0.01~0.03s-1. Moreover, the thermal processing map was verified by microstructure analysis.
Isothermal compression tests of NiPt15 alloys at temperatures ranging from 950 to 1150℃ and strain rates from 0.01 to 3s-1 were performed on Gleeble-3500 thermo-simulation machine. Based on stress-strain relationship curve of NiPt15 and hot processing maps during the hot deformation process were established. The power dissipation situation of NiPt15 alloy at different stage were analyzed. The damage instability mechanism of NiPt15 alloy was elucidated. According to the dynamic material model presented by Prasad, hot processing maps for hot working condition were established based on the effect of power dissipation and instability coefficient associated with various kinds of temperatures and stain rates. The results showed that the deformation temperature is the main factor affection of the curve variation trend and dynamic recrystallization. Moreover, the higher of deformation temperature and the lower of deformation rate, the dynamic recrystallization will be the more sufficient. Subsequently, the instability mechanism of NiPt15 alloy in thermal processing mainly included local plastic deformation, shear deformation zone and cracking. With the increase of true strain, local plastic deformation occured firstly, then shear deformation zone replaced it, and finally it evolved into cracking. The excellent safe processing zone for NiPt15 alloy were mainly concentrated in the non-instability zone . That was to say, the deformation parameters were within the range of 1000~1100℃, 0.03~0.1s-1 and 1100~1130℃, 0.01~0.03s-1. Moreover, the thermal processing map was verified by microstructure analysis.
2021, 50(11):4157-4164.
DOI: 10.12442/j.issn.1002-185X.20210268
Abstract:
In order to obtain high precision Al-Cu-Mg aluminium alloy isothermal extrusion parts with large extrusion ratio, it is necessary to accurately control the uniform exit temperature and deformation microstructure. Therefore, based on arbitrary Lagrange Eulerian (ALE) method, the isothermal extrusion process was simulated by ABAQUS finite element software. True stress-true strain curves of Al-Cu-Mg alloy at different temperature and strain rate were investigated by hot compression test. A new multi-physics coupling numerical model for isothermal extrusion process was established. The influence of extrusion speed, billet temperature and die temperature on the exit temperature and the distribution characteristics of the temperature field and strain rate field of extrusion products are studied; The isothermal extrusion was conducted to verify the model through the EBSD analysis and mechanical properties test of the deformed material. The results show that: 0.5mm/s extrusion speed can keep the exit temperature basically constant, in which the billet temperature is 450℃, cylinder temperature is 430℃, and die temperature is 400℃. After extrusion, the grains of the sample are significantly refined, and the preferred arrangement is to form < 111 > silk texture parallel to the extrusion direction, showing excellent tensile properties.
In order to obtain high precision Al-Cu-Mg aluminium alloy isothermal extrusion parts with large extrusion ratio, it is necessary to accurately control the uniform exit temperature and deformation microstructure. Therefore, based on arbitrary Lagrange Eulerian (ALE) method, the isothermal extrusion process was simulated by ABAQUS finite element software. True stress-true strain curves of Al-Cu-Mg alloy at different temperature and strain rate were investigated by hot compression test. A new multi-physics coupling numerical model for isothermal extrusion process was established. The influence of extrusion speed, billet temperature and die temperature on the exit temperature and the distribution characteristics of the temperature field and strain rate field of extrusion products are studied; The isothermal extrusion was conducted to verify the model through the EBSD analysis and mechanical properties test of the deformed material. The results show that: 0.5mm/s extrusion speed can keep the exit temperature basically constant, in which the billet temperature is 450℃, cylinder temperature is 430℃, and die temperature is 400℃. After extrusion, the grains of the sample are significantly refined, and the preferred arrangement is to form < 111 > silk texture parallel to the extrusion direction, showing excellent tensile properties.
2021, 50(11):4165-4173.
DOI: 10.12442/j.issn.1002-185X.20200890
Abstract:
Due to good corrosion resistance and mechanical properties, NiTi shape memory alloy (NiTi-SMA) has been widely used in oral and clinical medicine. However, the release of Ni2+ after NiTi-SMA corrosion can trigger cytotoxicity and allergic reactions. Improving the corrosion resistance of NiTi-SMA is one of the key technologies in biomedical materials field. In this paper, the corrosion status of NiTi-SMA commonly used in oral and clinical medicine in recent years was summarized. At the same time, the additive manufacturing and surface modification of NiTi-SMA technology was also reviewed in order to provide some guidance for the development of high performance anti-corrosion NiTi-SMA.
Due to good corrosion resistance and mechanical properties, NiTi shape memory alloy (NiTi-SMA) has been widely used in oral and clinical medicine. However, the release of Ni2+ after NiTi-SMA corrosion can trigger cytotoxicity and allergic reactions. Improving the corrosion resistance of NiTi-SMA is one of the key technologies in biomedical materials field. In this paper, the corrosion status of NiTi-SMA commonly used in oral and clinical medicine in recent years was summarized. At the same time, the additive manufacturing and surface modification of NiTi-SMA technology was also reviewed in order to provide some guidance for the development of high performance anti-corrosion NiTi-SMA.
Zhang Mai
,
Zhao Yunsong
,
Guo Yuanyuan
,
Wang Haiwen
,
Cui Lili
,
Yang Gong
,
Zhang Jian
,
Yao Zhihao
2021, 50(11):4174-4184.
DOI: 10.12442/j.issn.1002-185X.20200924
Abstract:
Cast nickel-base superalloy are widely used in hot end components such as turbine blades of aeroengines because of its excellent high temperature performance. Aeroengine turbine blade is one of the parts with the worst working environment and the most complicated structure. The structure of aeroengine turbine blade is very complex and its working environment is also very bad. The alloy bears serious stress and strain cycle damage nnder the action of high temperature alternating stress produced during engine operation. And cracks often initiation and further development in these weak areas, resulting in low cycle fatigue failure of the alloy, which seriously affects the service life of the alloy. Therefore, the research on the fatigue performance of the alloy is particularly important. In this paper, four factors affecting the low cycle fatigue properties of cast nickel-base superalloy are described in detail, including surface defects, internal structure and defects, crystal orientation and test conditions. Based on the characteristics of dislocation movement mode and morphology, the deformation mechanism of cast nickel-base superalloy at different temperatures is studied. Finally, the prediction methods of low cycle fatigue life are summarized.
Cast nickel-base superalloy are widely used in hot end components such as turbine blades of aeroengines because of its excellent high temperature performance. Aeroengine turbine blade is one of the parts with the worst working environment and the most complicated structure. The structure of aeroengine turbine blade is very complex and its working environment is also very bad. The alloy bears serious stress and strain cycle damage nnder the action of high temperature alternating stress produced during engine operation. And cracks often initiation and further development in these weak areas, resulting in low cycle fatigue failure of the alloy, which seriously affects the service life of the alloy. Therefore, the research on the fatigue performance of the alloy is particularly important. In this paper, four factors affecting the low cycle fatigue properties of cast nickel-base superalloy are described in detail, including surface defects, internal structure and defects, crystal orientation and test conditions. Based on the characteristics of dislocation movement mode and morphology, the deformation mechanism of cast nickel-base superalloy at different temperatures is studied. Finally, the prediction methods of low cycle fatigue life are summarized.
2021, 50(11):4185-4192.
DOI: 10.12442/j.issn.1002-185X.20200921
Abstract:
Ferromagnetic shape memory alloy Ni-Mn-Ga has large strain output and quick response, which would expect to be an intelligent material applied in actuator and sensor. It’s thermal, mechanical and magnetic properties are very sensitive to the chemical composition. The detail of composition dependence of these properties is reviewed in this paper. The changes of martensitic structure, martensitic transformation temperature and Curie temperature are clarified, the variation tendencies of the magnetocrystalline anisotropy energy and saturation magnetization are summarized, and the mechanism that doping elements reduce the twinning stress of martensite is revealed. Finally, the problems existing in the composition design of Ni-Mn-Ga alloy were discussed.
Ferromagnetic shape memory alloy Ni-Mn-Ga has large strain output and quick response, which would expect to be an intelligent material applied in actuator and sensor. It’s thermal, mechanical and magnetic properties are very sensitive to the chemical composition. The detail of composition dependence of these properties is reviewed in this paper. The changes of martensitic structure, martensitic transformation temperature and Curie temperature are clarified, the variation tendencies of the magnetocrystalline anisotropy energy and saturation magnetization are summarized, and the mechanism that doping elements reduce the twinning stress of martensite is revealed. Finally, the problems existing in the composition design of Ni-Mn-Ga alloy were discussed.
