Ti60合金的热变形行为及工艺参数优化

Hot deformation behavior and process parameter optimization of Ti60 alloy

摘要:

在变形温度600～950℃,应变速率0.001～10s_^-1条件下,采用Thermecmaster-Z型热加工模拟试验机对Ti60合金进行等温恒应变速率压缩实验。通过分析流动应力行为,计算应变速率敏感指数m和应变硬化指数n,并综合考虑加工图和变形微观组织来研究该合金的热变形行为,得到优化的工艺参数范围。研究结果表明,Ti60合金的流动应力-应变曲线在不同热力参数条件下分别呈现流动稳态型和流动软化型。应变速率敏感指数m随着变形温度升高和应变速率降低而增大。应变硬化指数n随着变形温度升高而减小；随着应变速率的增加在低应变速率(0.001～0.1s_^-1)区间增大,在高应变速率(1～10s_^-1)区间减小；随着应变的增加在高温段(800～950℃)的低应变速率(0.001～0.1s_^-1)区间较缓慢地减小,在高温段(800～950℃)的高应变速率(1～10s_^-1)区间以及低温段(600～750℃)的所有应变速率(0.001～10s_^-1)区间较明显地减小。Ti60合金存在两个功率耗散效率峰值区域,其对应的热力参数窗口分别为温度725～875℃,应变速率≤0.003s_^-1和温度875～938℃,应变速率≤0.04s_^-1。从流动应力行为、应变速率敏感指数m、应变硬化指数n以及加工图综合考虑,Ti60合金的最佳热加工工艺参数为：温度800～875℃,应变速率0.001～0.003s_^-1,或温度875～938℃,应变速率0.001～0.04s_^-1。

Abstract:

The isothermal compression tests of Ti60 alloy were conducted on the Thermecmaster-Z thermal simulator at deformation temperature of 600～950℃, strain rate 0.001～10s_^-1. The hot deformation behavior of Ti60 alloy were investigated, by analyzing the flow stress behavior, calculating the strain rate sensitive exponent m and strain hardening exponent n, along with the processing map and deformation microstructure, to optimize processing parameter. The results show that the flow stress-strain curve of Ti60 alloy presents flow steady state and flow softening respectively at different processing parameters. The strain rate sensitivity exponent m increases with the increase of deformation temperature and decrease of strain rate. The strain hardening exponent n decreases with the increase of deformation temperature. With the increase of strain rate, n increases in the low strain rate (0.001～0.1s_^-1) and decreases in the high strain rate (1～10s_^-1). With the increase of strain, n decreased slowly at the low strain rate (0.001～0.1s_^-1), the high temperature (800～950℃), while which decreased significantly at the high strain rate (1～10s_^-1) , the high temperature section (800～950℃) and all the strain rates (0.001～10s_^-1), the low temperature (600～750℃). Ti60 alloy has two peak power dissipation efficiency regions, whose corresponding processing parameter Windows : temperature 725～875℃, strain rate ≤0.003s_^-1 and temperature 875～938℃, strain rate ≤0.04s_^-1, respectively. Considering the flow stress behavior, strain rate sensitivity exponent m, strain hardening exponent n and processing map, the optimal thermal processing parameters of Ti60 alloy: temperature 800～875℃, strain rate 0.001～0.003s_^-1, or temperature 875～938℃, strain rate 0.001～0.04s_^-1.