Cylindrical samples of Ni-based GH4037 alloy were compressed at solid temperatures(1200,1250 and 1300℃) and semi-solid temperatures(1340,1350,1360,1370 and 1380℃) with different strain rates of 0.01,0.1 and 1 s-1.Hi...Cylindrical samples of Ni-based GH4037 alloy were compressed at solid temperatures(1200,1250 and 1300℃) and semi-solid temperatures(1340,1350,1360,1370 and 1380℃) with different strain rates of 0.01,0.1 and 1 s-1.High temperature deformation behavior and microstructure evolution of GH4037 alloy were investigated.The results indicated that flow stress decreased rapidly at semi-solid temperatures compared to that at solid temperatures.Besides,the flow stress continued to increase after reaching the initial peak stress at semi-solid temperatures when the strain rate was 1 s-1.With increasing the deformation temperature,the size of initial solid grains and recrystallized grains increased.At semi-solid temperatures,the grains were equiaxed,and liquid phase existed at the grain boundaries and inside the grains.Discontinuous dynamic recrystallization(DDRX) characterized by grain boundary bulging was the main nucleation mechanism for GH4037 alloy.展开更多
An equal channel reciprocating extrusion(ECRE)was proposed first to obtain a severe plastic deformation(SPD)of 7005 alloy.The microstructure and mechanical properties of one-pass ECREed(ECRE processed)7005 alloy were ...An equal channel reciprocating extrusion(ECRE)was proposed first to obtain a severe plastic deformation(SPD)of 7005 alloy.The microstructure and mechanical properties of one-pass ECREed(ECRE processed)7005 alloy were investigated.The results show that SPD occurring in ECRE leads to a mixed microstructure.ECREed 7005 alloy exhibits a significant improvement of ultimate tensile strength(UTS)and elongation.Mechanical properties in the region undergoing a complete ECRE process are higher than those in the region undergoing an incomplete ECRE process due to larger dislocation strengthening effect.Yield strength(YS)and UTS first decrease and then increase with an increase of extrusion temperature.The YS of 359.2 MPa,UTS of 490 MPa and elongation of 17.7%are obtained after T6 treatment.Fine-grain strengthening,dislocation strengthening and precipitation strengthening in the T6-treated ECREed sample all play important roles in improving the mechanical properties.展开更多
To shorten the preparation process of semi-solid billets,semi-solid billets of 2A14 aluminum alloy were prepared by wrought aluminum directly semi-solid isothermal treatment(WADSSIT)process.Three-dimension(3D)combined...To shorten the preparation process of semi-solid billets,semi-solid billets of 2A14 aluminum alloy were prepared by wrought aluminum directly semi-solid isothermal treatment(WADSSIT)process.Three-dimension(3D)combined microstructure evolution,namely transverse direction(TD)surface,rolling direction(RD)surface,and normal direction(ND)surface,was studied.Effects of temperature and holding time on average grain size and average shape factor were investigated.The results showed that the optimum conditions for preparation of 2A14 semi-solid billets by this process were 615℃ and 20 min(average grain size of 124μm and shape factor of 0.81).Electron backscatter diffraction(EBSD)observations indicated that the microstructure was completely recrystallized when it was heated to 600℃.Grain size was increased with the increase of temperature and grew up slowly with the holding time prolonging.Roundness was increased with increase of holding time but was not sensitive to temperature.展开更多
基金the National High Technology Research and Development Program of China(No.2019YFB2006503)the National Natural Science Foundation of China(No.51875124).
基金Project(51575127)supported by the National Natural Science Foundation of China
文摘Cylindrical samples of Ni-based GH4037 alloy were compressed at solid temperatures(1200,1250 and 1300℃) and semi-solid temperatures(1340,1350,1360,1370 and 1380℃) with different strain rates of 0.01,0.1 and 1 s-1.High temperature deformation behavior and microstructure evolution of GH4037 alloy were investigated.The results indicated that flow stress decreased rapidly at semi-solid temperatures compared to that at solid temperatures.Besides,the flow stress continued to increase after reaching the initial peak stress at semi-solid temperatures when the strain rate was 1 s-1.With increasing the deformation temperature,the size of initial solid grains and recrystallized grains increased.At semi-solid temperatures,the grains were equiaxed,and liquid phase existed at the grain boundaries and inside the grains.Discontinuous dynamic recrystallization(DDRX) characterized by grain boundary bulging was the main nucleation mechanism for GH4037 alloy.
基金This work is supported by the National Natural Science Foundation of China(51875124).
文摘An equal channel reciprocating extrusion(ECRE)was proposed first to obtain a severe plastic deformation(SPD)of 7005 alloy.The microstructure and mechanical properties of one-pass ECREed(ECRE processed)7005 alloy were investigated.The results show that SPD occurring in ECRE leads to a mixed microstructure.ECREed 7005 alloy exhibits a significant improvement of ultimate tensile strength(UTS)and elongation.Mechanical properties in the region undergoing a complete ECRE process are higher than those in the region undergoing an incomplete ECRE process due to larger dislocation strengthening effect.Yield strength(YS)and UTS first decrease and then increase with an increase of extrusion temperature.The YS of 359.2 MPa,UTS of 490 MPa and elongation of 17.7%are obtained after T6 treatment.Fine-grain strengthening,dislocation strengthening and precipitation strengthening in the T6-treated ECREed sample all play important roles in improving the mechanical properties.
基金financially supported by the National Natural Science Foundation of China (No.51875124)the National Key Research and Development Project,China (No.2019YFB2006503)。
文摘To shorten the preparation process of semi-solid billets,semi-solid billets of 2A14 aluminum alloy were prepared by wrought aluminum directly semi-solid isothermal treatment(WADSSIT)process.Three-dimension(3D)combined microstructure evolution,namely transverse direction(TD)surface,rolling direction(RD)surface,and normal direction(ND)surface,was studied.Effects of temperature and holding time on average grain size and average shape factor were investigated.The results showed that the optimum conditions for preparation of 2A14 semi-solid billets by this process were 615℃ and 20 min(average grain size of 124μm and shape factor of 0.81).Electron backscatter diffraction(EBSD)observations indicated that the microstructure was completely recrystallized when it was heated to 600℃.Grain size was increased with the increase of temperature and grew up slowly with the holding time prolonging.Roundness was increased with increase of holding time but was not sensitive to temperature.