基于加工图的塑性失稳准则比较研究

A Comparative Study of Various Flow Instability Criteria in Processing Map

摘要:

介绍基于加工图理论的各种塑性失稳准则，比较分析各个准则的区别，以及各参数的物理意义，并以Ti2AlNb基合金为研究对象建立Prasad、Murty、Gegel和Malas准则的热加工图。结合试验结果分析和对比4种塑性失稳准则下加工图的区别发现：Prasad和Murty准则的塑性失稳图相似，均位于高应变速率区，且Murty准则的塑性失稳区稍窄；Gegel和Malas准则的塑性失稳图相似，塑性失稳区比Prasad和Murty准则的明显偏大，除高应变速率外，还能预测高温低应变速率的塑性失稳现象；解释可能出现各种失稳现象的原因，并结合各种塑性失稳准则提出判断材料塑性变形失稳的选用原则。

Abstract:

Four instability criteria, namely Murty, Gegel, Malas and Prasad criteria, were compared, and the physical significance of parameters was analyzed in this paper. It is indicated that the instability map developed by Murty criterion is similar to Prasad criterion, showing an unstable flow at high strain rates. Murty criterion exhibits a little narrower unstable region. The instability maps developed by Malas criterion and Gegel criterion have similar shapes, and the unstable regions are wider than those Prasad criterion and Murty criterion. In addition to the unstable flow at high strain rates as predicted by Murty criterion and Prasad criterion, Malas criterion and Gegel criterion have a good ability for predicting unstable flow at high temperatures and low strain rates. The processing maps were validated by hot compression tests of Ti-22Al-25Nb alloy, and the possible causes of various instability were discussed.