TA12钛合金热变形微观组织演变及变形参数优化

Microstructure evolution and parameters optimization during hot deformation of TA12 titanium alloy

在应变速率为0.01-10s^-1,变形温度为870-1070 ℃,最大变形量为80% 的条件下,利用Gleeble-3800热模拟机对TA12合金高温压缩变形行为进行研究.依据实验结果绘制真应力-应变曲线,分析变形参数与组织的关系.同时把应力-应变曲线作为计算应变速率敏感指数m 、功率耗散因子η、失稳判据ξ 的底层数据,研究应变速率、变形温度、变形量共同存在对应变速率敏感指数m 、功率耗散因子η 的影响,绘制失稳图对失稳区域进行识别,并将功率耗散图和失稳图叠加构建热加工图.结果表明,在变形温度较低时,温度的影响主要表现为α 相形态和数量的变化,在变形温度较高时,主要表现为β 晶粒粗化;应变速率的影响主要表现在变形时间上;较高的η 和ξ 区域为良好加工区域,较低的η 和ξ 的失稳变形参数区域为加工避免区域.本批次合金适宜加工参数为温度910-970℃,应变速率0.01-0.3s^-1.

The hot deformation behaviors of TA12 alloy with the strain of 80%,strain rate range of 0. 01-10 s- 1and temperature range of 870-1 070 ℃ was studied by using Gleeble-3800 thermal simulation machine. The true flow stress-true strain curves of TA12 were obtaind on the basis of the experimental parameters,and the influence of deformation parameters on the organization and the organization evolution were analyzed. Meanwhile,the strain rate sensitivity index m,power dissipation factor η,instability criterion ξ were calculated based on the underlying data from the stress strain curve. A variety of mechanisms of conversion produced by combined effect of stress,strain rate,deformation temperature and deformation were analyzed. Instability areas were identified by drawing instability figures further. Moreover,hot working figures were constructed though overlaying power dissipation figure and instability figure. The results show that:at low temperature,the main influence of the temperature included changes in α phase morphology and the number,and at high temperature,the main performance was β grain coarsening; the influence of strain rate was mainly manifested in deformation time; the higher area of η and ξ was a good processing area,the lower instability deformation parameters area of η and ξ was an avoided processing area. the appropriate processing condition of this alloy was temperature of 910-970 ℃,strain rate of 0. 01-0. 3 s- 1.