The effect of hot deformation on the quench sensitivity of the 7085 alloy was studied through hardness testing and microstructure characterization.The findings indicate that hot deformation enhances the quench sensiti...The effect of hot deformation on the quench sensitivity of the 7085 alloy was studied through hardness testing and microstructure characterization.The findings indicate that hot deformation enhances the quench sensitivity of the 7085 alloy,with the hardness difference between water quenching and air cooling increasing from 5.4%(before hot deformation)to 10.4%(after hot deformation).In the undeformed samples,the Al3Zr particles within the grains exhibit better coherent with the Al matrix.During slow quenching,only theηphase is observed on Al3Zr particles and at the grain boundaries.Hot deformation leads to a mass of recrystallization and the formation of subgrains with high dislocation density.This results in an increase in the types,quantities,and sizes of heterogeneous precipitates during quenching.In the slow quenching process,high angle grain boundaries are best for the nucleation and growth of theηphase.Secondly,a substantial quantity ofηand T phases precipitate on the non-coherent Al3Zr phase within the recrystallized grains.The locations with high dislocation density subgrains(boundaries)serve as nucleation positions for theηand T phases precipitating.Additionally,the Y phase is observed to precipitate at dislocation sites within the subgrains.展开更多
In this study,the Mg-3Zn-0.5Zr-χNd(χ=0,0.6)alloys were subjected to final rolling treatment with large deformation of 50%.The impact of annealing temperatures on the microstructure and mechanical properties was inve...In this study,the Mg-3Zn-0.5Zr-χNd(χ=0,0.6)alloys were subjected to final rolling treatment with large deformation of 50%.The impact of annealing temperatures on the microstructure and mechanical properties was investigated.The rolled Mg-3Zn-0.5Zr-0.6Nd alloy exhibited an ultimate tensile strength of 386 MPa,a yield strength of 361 MPa,and an elongation of 7.1%.Annealing at different temperatures resulted in reduced strength and obviously increased elongation for both alloys.Optimal mechanical properties for the Mg-3Zn-0.5Zr-0.6Nd alloy were achieved after annealing at 200℃,with an ultimate tensile strength of 287 MPa,a yield strength of 235 MPa,and an elongation of 26.1%.The numerous deformed microstructures,twins,and precipitated phases in the rolled alloy could impede the deformation at room temperature and increase the work hardening rate.After annealing,a decrease in the work hardening effect and an increase in the dynamic recovery effect were obtained due to the formation of fine equiaxed grains,and the increased volume fraction of precipitated phases,which significantly improved the elongation of the alloy.Additionally,the addition of Nd element could enhance the annealing recrystallization rate,reduce the Schmid factor difference between basal and prismatic slip systems,facilitate multi-system slip initiation and improve the alloy plasticity.展开更多
The effects of low temperature thermo-mechanical treatment （LTTMT） on microstructures and mechanical properties of Ti-6Al-4V （TC4） alloy were studied by optical microscopy （OM）, tensile test, scanning electron m...The effects of low temperature thermo-mechanical treatment （LTTMT） on microstructures and mechanical properties of Ti-6Al-4V （TC4） alloy were studied by optical microscopy （OM）, tensile test, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The experimental results confirm that the strength of TC4 alloy can be improved obviously by LTTMT processing, which combines strain strengthening with aging strengthening. The effect of LTTMT on the alloy depends on the microstructure of the refined and dispersed a＋fl phase on the basis of high dislocation density by pre-deformation below recrystallization temperature. The tensile strength decreases with the increase of pre-deformation reduction. The optimal processing parameters of LTTMT for TC4 alloy are as follows： solution treatment at 900 ℃ for 15 min, pre-deformation in the range of 600-700 ℃ with a reduction of 35%, finally aging at 540 ℃ for 4 h followed by air-cooling.展开更多
In order to establish a model between the grain size and the process parameters, the hot deformation behaviors of Ti 49.5Al alloy was investigated by isothermal compressive tests at temperatures ranging from 800 to 1?...In order to establish a model between the grain size and the process parameters, the hot deformation behaviors of Ti 49.5Al alloy was investigated by isothermal compressive tests at temperatures ranging from 800 to 1?100 ℃ with strain rates of 10 -3 10 -1 s -1 . Within this range, the deformation behavior obeys the power law relationship, which can be described using the kinetic rate equation. The stress exponent, n , has a value of about 5.0, and the apparent activation energy is about 320 J/mol, which fits well with the value estimated in previous investigations. The results show that, the dependence of flow stress on the recrystallized grain size can be expressed by the equation: σ=K 1d rex -0 56 . The relationship between the deformed microstructure and the process control parameter can be expressed by the formula: lg d rex =-0 281?1gZ +3 908?1.展开更多
The electronic packaging shell with high silicon carbide aluminum-base composites was prepared by semi-solid thixoforming technique. The flow characteristic of the Si C particulate was analyzed. The microstructures of...The electronic packaging shell with high silicon carbide aluminum-base composites was prepared by semi-solid thixoforming technique. The flow characteristic of the Si C particulate was analyzed. The microstructures of different parts of the shell were observed by scanning electron microscopy and optical microscopy, and the thermophysical and mechanical properties of the shell were tested. The results show that there exists the segregation phenomenon between the Si C particulate and the liquid phase during thixoforming, the liquid phase flows from the shell, and the Si C particles accumulate at the bottom of the shell. The volume fraction of Si C decreases gradually from the bottom to the walls. Accordingly, the thermal conductivities of bottom center and walls are 178 and 164 W·m-1·K-1, the coefficients of thermal expansion(CTE) are 8.2×10-6 and 12.6×10-6 K-1, respectively. The flexural strength decreases slightly from 437 to 347 MPa. The microstructures and properties of the shell show gradient distribution.展开更多
基金Project(52205421)supported by the National Natural Science Foundation of ChinaProject(AA23023028)supported by the Guangxi Science and Technology Major Project,China+2 种基金Projects(2022B0909070001,2020B010186001)supported by the Key Research and Development Projects of Guangdong Province,ChinaProject(2021B0101220006)supported by the Guangdong Key Areas Research and Development Program“Chip,Software and Computing”Major Project,ChinaProjects(2021RC2087,2022JJ30570)supported by the Science and Technology Innovation Program of Hunan Province,China。
文摘The effect of hot deformation on the quench sensitivity of the 7085 alloy was studied through hardness testing and microstructure characterization.The findings indicate that hot deformation enhances the quench sensitivity of the 7085 alloy,with the hardness difference between water quenching and air cooling increasing from 5.4%(before hot deformation)to 10.4%(after hot deformation).In the undeformed samples,the Al3Zr particles within the grains exhibit better coherent with the Al matrix.During slow quenching,only theηphase is observed on Al3Zr particles and at the grain boundaries.Hot deformation leads to a mass of recrystallization and the formation of subgrains with high dislocation density.This results in an increase in the types,quantities,and sizes of heterogeneous precipitates during quenching.In the slow quenching process,high angle grain boundaries are best for the nucleation and growth of theηphase.Secondly,a substantial quantity ofηand T phases precipitate on the non-coherent Al3Zr phase within the recrystallized grains.The locations with high dislocation density subgrains(boundaries)serve as nucleation positions for theηand T phases precipitating.Additionally,the Y phase is observed to precipitate at dislocation sites within the subgrains.
基金Project(202203021221088)supported by the Fundamental Research Program of Shanxi Province,ChinaProject(20230010)supported by the Fund Program for the Scientific Activities of Selected Returned Overseas Professionals in Shanxi Province,China+5 种基金Project(202201050201012)supported by the Shanxi Provincial Science and Technology Major Special Project Plan of Taking the Lead in Unveiling the List,ChinaProject(2023-063)supported by the Research Project Supported by Shanxi Scholarship Council of ChinaProjects(51771129,52271109)supported by the National Natural Science Foundation of ChinaProject(2021YFB3703300)supported by the National Key Research and Development Program for Young Scientists,ChinaProject(YDZJSX2021B019)supported by the Special Fund Project for Guiding Local Science and Technology Development by the Central Government,ChinaProject(SKL-YSJ202103)supported by the Open Foundation of State Key Laboratory of High-end Compressor and System Technology,China。
文摘In this study,the Mg-3Zn-0.5Zr-χNd(χ=0,0.6)alloys were subjected to final rolling treatment with large deformation of 50%.The impact of annealing temperatures on the microstructure and mechanical properties was investigated.The rolled Mg-3Zn-0.5Zr-0.6Nd alloy exhibited an ultimate tensile strength of 386 MPa,a yield strength of 361 MPa,and an elongation of 7.1%.Annealing at different temperatures resulted in reduced strength and obviously increased elongation for both alloys.Optimal mechanical properties for the Mg-3Zn-0.5Zr-0.6Nd alloy were achieved after annealing at 200℃,with an ultimate tensile strength of 287 MPa,a yield strength of 235 MPa,and an elongation of 26.1%.The numerous deformed microstructures,twins,and precipitated phases in the rolled alloy could impede the deformation at room temperature and increase the work hardening rate.After annealing,a decrease in the work hardening effect and an increase in the dynamic recovery effect were obtained due to the formation of fine equiaxed grains,and the increased volume fraction of precipitated phases,which significantly improved the elongation of the alloy.Additionally,the addition of Nd element could enhance the annealing recrystallization rate,reduce the Schmid factor difference between basal and prismatic slip systems,facilitate multi-system slip initiation and improve the alloy plasticity.
基金Project(2008WK2005) supported by the Science and Technology Plan of Hunan Province, China
文摘The effects of low temperature thermo-mechanical treatment （LTTMT） on microstructures and mechanical properties of Ti-6Al-4V （TC4） alloy were studied by optical microscopy （OM）, tensile test, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The experimental results confirm that the strength of TC4 alloy can be improved obviously by LTTMT processing, which combines strain strengthening with aging strengthening. The effect of LTTMT on the alloy depends on the microstructure of the refined and dispersed a＋fl phase on the basis of high dislocation density by pre-deformation below recrystallization temperature. The tensile strength decreases with the increase of pre-deformation reduction. The optimal processing parameters of LTTMT for TC4 alloy are as follows： solution treatment at 900 ℃ for 15 min, pre-deformation in the range of 600-700 ℃ with a reduction of 35%, finally aging at 540 ℃ for 4 h followed by air-cooling.
文摘In order to establish a model between the grain size and the process parameters, the hot deformation behaviors of Ti 49.5Al alloy was investigated by isothermal compressive tests at temperatures ranging from 800 to 1?100 ℃ with strain rates of 10 -3 10 -1 s -1 . Within this range, the deformation behavior obeys the power law relationship, which can be described using the kinetic rate equation. The stress exponent, n , has a value of about 5.0, and the apparent activation energy is about 320 J/mol, which fits well with the value estimated in previous investigations. The results show that, the dependence of flow stress on the recrystallized grain size can be expressed by the equation: σ=K 1d rex -0 56 . The relationship between the deformed microstructure and the process control parameter can be expressed by the formula: lg d rex =-0 281?1gZ +3 908?1.
文摘The electronic packaging shell with high silicon carbide aluminum-base composites was prepared by semi-solid thixoforming technique. The flow characteristic of the Si C particulate was analyzed. The microstructures of different parts of the shell were observed by scanning electron microscopy and optical microscopy, and the thermophysical and mechanical properties of the shell were tested. The results show that there exists the segregation phenomenon between the Si C particulate and the liquid phase during thixoforming, the liquid phase flows from the shell, and the Si C particles accumulate at the bottom of the shell. The volume fraction of Si C decreases gradually from the bottom to the walls. Accordingly, the thermal conductivities of bottom center and walls are 178 and 164 W·m-1·K-1, the coefficients of thermal expansion(CTE) are 8.2×10-6 and 12.6×10-6 K-1, respectively. The flexural strength decreases slightly from 437 to 347 MPa. The microstructures and properties of the shell show gradient distribution.
