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
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.
基金Supported by the National Nature Science Foundation of China (50874086)Special Programs Foundation of Ministry of Education of Shaanxi Province (07JK307)the Nature Science Foundation of Shaanxi Province (2005E105)
文摘在室温,采用通道夹角为120°的变形模具对工业纯钛(Commercial Pure Titanium,CP-Ti)以Bc方式实施四道次ECAP(Equal Channel Angular Pressing)挤压变形,成功获得表面光滑无裂纹的变形试样。文中主要研究了工业纯钛在室温下进行ECAP多道次变形的组织结构演变,并测试了变形试样的力学性能。微观结构显示工业纯钛在室温下进行多道次ECAP变形时,只在前两道次产生了大量的变形孪晶,且随道次增加变形孪晶逐渐消失。最终获得的试样晶粒平均尺寸由最初的约28μm细化到约250nm,试样断裂强度和显微硬度分别提高到773和2486MPa,而试样仍保持较好的延伸率(可达16.8%)。
