镍钛形状记忆合金在热压缩变形下的动态回复和动态再结晶

通过获得镍钛形状记忆合金在应变速率(0.001～1 s-1)和变形温度(600～1000℃)下的压缩真实应力—应变曲线,研究镍钛形状记忆合金在热变形下的力学行为.通过显微组织演变研究镍钛形状记忆合金的动态回复和动态再结晶,获得应变速率、变形温度和变形程度对镍钛形状记忆合金的动态回复和动态再结晶的影响规律.镍钛形状记忆合金在600℃和700℃下,动态回复和动态再结晶共存,但在其他温度下表现出完全动态再结晶.增加变形温度或降低应变速率,导致较大的等轴晶粒.变形程度对镍钛形状记忆合金的动态再结晶具有重要的影响.在镍钛形状记忆合金的动态再结晶中存在临界变形程度,当大于临界变形程度时,较大的变形程度有助于获得细小的等轴再结晶晶粒.

Dynamic recovery and dynamic recrystallization of NiTi shape memory alloy under hot compression deformation

Mechanical behavior of nickel–titanium shape memory alloy (NiTi SMA) under hot deformation was investigated according to the true stress—strain curves of NiTi samples under compression at the strain rates of 0.001–1 s^?1 and at the temperatures of 600–1000 °C. Dynamic recovery and dynamic recrystallization of NiTi SMA were systematically investigated by microstructural evolution. The influence of the strain rates, the deformation temperatures and the deformation degree on the dynamic recovery and dynamic recrystallization of NiTi SMA was obtained as well. NiTi SMA was characterized by the combination of dynamic recovery and dynamic recrystallization at 600 °C and 700 °C, but the complete dynamic recrystallization occurred at other deformation temperatures. Increasing the deformation temperatures or decreasing the stain rates leads to larger equiaxed grains. The deformation degree has an important influence on the dynamic recrystallization of NiTi SMA. There exists the critical deformation degree during the dynamic recrystallization of NiTi SMA, beyond which the larger deformation degree contributes to obtaining the finer equiaxed grains.