TiNi and Ti-based shape memory alloys were processed by equal channel angular pressing （ECAP） at 673-773 K along Bc route to obtain ultrafine grains for increasing the strength of parent phase and improving the func...TiNi and Ti-based shape memory alloys were processed by equal channel angular pressing （ECAP） at 673-773 K along Bc route to obtain ultrafine grains for increasing the strength of parent phase and improving the functional properties. The effects of both thermodynamically stable and metastable second phases on the mechanical properties and martensitic transformations of these alloys were investigated. It is found that thermodynamically stable Ti2Ni phase has no effect on martensitic transformation and superelasticity of Ti-rich TiNi alloy, thermodynamically stable α phase is harmful for ductility of Ti-Mo-Nb-V-Al alloy, but metastable Ti3Ni4 phase is effective for R phase transformation, martensitic transformation and superelasticity of Ni-rich TiNi alloy. The mechanisms of the second phases on the martensitic transformations and mechanical properties were discussed.展开更多
7075 aluminum alloy was used to obtain elbow parts by complex thixoextrusion and the microstructure evolution and mechanical properties during this process were studied by SEM,TEM and other analytical methods.The resu...7075 aluminum alloy was used to obtain elbow parts by complex thixoextrusion and the microstructure evolution and mechanical properties during this process were studied by SEM,TEM and other analytical methods.The results show that different parts in 7075 aluminum alloy show quite different microstructures.The microstructure of the thin walls formed by back-extrusion is stratified,and the bottom of the parts formed by angular extrusion is obviously deformed.Shear forces contribute to the crushing of grains and the coarse second phase.The main strengthening phases in the material areηphase and E phase,whose amounts greatly decrease during heating to semi-solid and thixoextrusion.After heat treatment,they can precipitate evenly to improve the mechanical properties of the material.The average tensile strength of whole part after thixoextrusion and heat treatment is 485.49 MPa,while the average elongation is 5.49%.展开更多
基金Project (50671067) supported by the National Natural Science Foundation of ChinaProject (09JC1407200) supported by the Science and Technology Committee of Shanghai, China
文摘TiNi and Ti-based shape memory alloys were processed by equal channel angular pressing （ECAP） at 673-773 K along Bc route to obtain ultrafine grains for increasing the strength of parent phase and improving the functional properties. The effects of both thermodynamically stable and metastable second phases on the mechanical properties and martensitic transformations of these alloys were investigated. It is found that thermodynamically stable Ti2Ni phase has no effect on martensitic transformation and superelasticity of Ti-rich TiNi alloy, thermodynamically stable α phase is harmful for ductility of Ti-Mo-Nb-V-Al alloy, but metastable Ti3Ni4 phase is effective for R phase transformation, martensitic transformation and superelasticity of Ni-rich TiNi alloy. The mechanisms of the second phases on the martensitic transformations and mechanical properties were discussed.
文摘7075 aluminum alloy was used to obtain elbow parts by complex thixoextrusion and the microstructure evolution and mechanical properties during this process were studied by SEM,TEM and other analytical methods.The results show that different parts in 7075 aluminum alloy show quite different microstructures.The microstructure of the thin walls formed by back-extrusion is stratified,and the bottom of the parts formed by angular extrusion is obviously deformed.Shear forces contribute to the crushing of grains and the coarse second phase.The main strengthening phases in the material areηphase and E phase,whose amounts greatly decrease during heating to semi-solid and thixoextrusion.After heat treatment,they can precipitate evenly to improve the mechanical properties of the material.The average tensile strength of whole part after thixoextrusion and heat treatment is 485.49 MPa,while the average elongation is 5.49%.
