Super-Elasticity Characteristics of TiNi Alloy Processed by Equal Channel Angular Extrusion
来源期刊：稀有金属材料与工程2009年增刊第3期
论文作者：Fan Zhiguo Jiang Hong Xie Chaoying
关键词：equal channel angular extrusion; TiNi shape memory alloy; R-phase transformation; martensitic transformation; super-elasticity;
摘 要：A Ni-rich TiNi alloy was processed by Equal Channel Angular Extrusion (ECAE) at 500℃. After four passes ECAE treatment, microstructure of the alloy was refined but slightly inhomogeneous, to sub-micron scale, approximately 0.5～0.6 μm. Comparing with the solution-treated TiNi specimen, the martensitic transformations start (M_s) and peak temperatures (M_p) of TiNi specimens processed by ECAE were dramatically lowered. After ECAE treatment, the R-phase transformation was stimulated and separated from martensitic transformation, but occurred within a larger temperature range. Super-elasticity characteristics of TiNi alloy were tested by tensile loading and unloading cycles. The results revealed that at a tensile strain of 6% or smaller, TiNi alloy processed by four passes ECAE showed better super-elasticity, with less residual strain retained, than solution-treated sample. After tensile strain exceeded 6%, up to 8%, the maximum recoverable strain of TiNi alloy ECAE treated was decreased. Microstructure evolution and its effect on phase transformations and super-elasticity characteristics were discussed.
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摘要:A Ni-rich TiNi alloy was processed by Equal Channel Angular Extrusion (ECAE) at 500℃. After four passes ECAE treatment, microstructure of the alloy was refined but slightly inhomogeneous, to sub-micron scale, approximately 0.5～0.6 μm. Comparing with the solution-treated TiNi specimen, the martensitic transformations start (M_s) and peak temperatures (M_p) of TiNi specimens processed by ECAE were dramatically lowered. After ECAE treatment, the R-phase transformation was stimulated and separated from martensitic transformation, but occurred within a larger temperature range. Super-elasticity characteristics of TiNi alloy were tested by tensile loading and unloading cycles. The results revealed that at a tensile strain of 6% or smaller, TiNi alloy processed by four passes ECAE showed better super-elasticity, with less residual strain retained, than solution-treated sample. After tensile strain exceeded 6%, up to 8%, the maximum recoverable strain of TiNi alloy ECAE treated was decreased. Microstructure evolution and its effect on phase transformations and super-elasticity characteristics were discussed.
关键词:equal channel angular extrusion; TiNi shape memory alloy; R-phase transformation; martensitic transformation; super-elasticity;
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