等原子比NiTi形状记忆合金高温塑性变形本构方程和热加工图

摘要

In order to describe the deformation behavior and the hot workability of equiatomic NiTi shape memory alloy (SMA) during hot deformation, Arrhenius-type constitutive equation and hot processing map of the alloy were developed by hot compression tests at temperatures ranging from 500 to 1100 °C and strain rates ranging from 0.0005 to 0.5 s−1. The results show that the instability region of the hot processing map increases with the increase of deformation extent. The instability occurs in the low and high temperature regions. The instability region presents the adiabatic shear bands at low temperatures, but it exhibits the abnormal growth of the grains at high temperatures. Consequently, it is necessary to avoid processing the equiatomic NiTi SMA in these regions. It is preferable to process the NiTi SMA at the temperatures ranging from 750 to 900 °C.%为了描述等原子比NiTi形状记忆合金在高温下的变形行为和热加工性能，通过在温度范围为500~1100°C和应变速率范围为0.0005~0.5 s−1的热压缩实验构建了该合金的Arrhenius型本构方程和热加工图。结果表明：热加工图的失稳区随着变形程度的增加而增大。失稳发生在低温区和高温区，低温区的失稳特征表现为绝热剪切带，而高温区的失稳特征则表现为晶粒的异常长大。因此，必须避免在这些失稳区域加工该等原子比NiTi形状记忆合金。加工该NiTi形状记忆合金的最佳温度范围为750~900°C。