两种冶炼工艺下A286高温合金的热变形行为

为了探究真空感应+真空自耗(VIM+VAR)和电炉+精炼+真空自耗(EAF+LF+VAR)两种工艺冶炼A286高温合金的热变形行为,利用Gleeble-3800热模拟试验机在温度950~1150 ℃和应变速率0.01~10 s^-1范围内进行热压缩试验。基于摩擦和绝热加热修正后的真应力-真应变曲线和应变硬化率曲线建立了A286合金的Arrhenius本构方程,确定了VIM+VAR合金和EAF+LF+VAR合金的热激活能分别为358.15和372.54 kJ·mol^-1。利用临界应变和动态再结晶体积分数50%应变引入动态再结晶速度参数k_v,建立新的动态再结晶模型。采用Prasad 准则绘制两种钢在应变0.2、0.5和0.9下的热加工图,并结合组织分析,确定VIM+VAR合金的最佳热加工工艺条件为1050~1100 ℃,0.01~1 s^-1和1100~1150 ℃,0.1~10 s^-1;EAF+LF+VAR合金的最佳热加工工艺条件为1050~1100 ℃,0.01~1 s^-1和1100~1150 ℃,0.1~3 s^-1,得出VIM+VAR合金的热加工区间较宽,其热加工性能优于EAF+LF+VAR合金。

Hot deformation behavior of A286 superalloy with two different smelting processes

In order to investigate the hot deformation behavior of A286 superalloy with two smelting processes of VIM+VAR (vacuum induction melting+vacuum arc remelting) and EAF+LF+VAR (electric arc furnace+ladle furnace+vacuum arc remelting), hot compression tests were carried out on a Gleeble-3800 hot simulation test machine at temperatures ranging from 950 to 1150 ℃ and strain rates ranging from 0.01 to 10 s^-1. The Arrhenius constitutive equations of the A286 alloy are established based on the true stress-true strain curves and work hardening rate curves modified by friction and adiabatic heating. The hot deformation activation energies of the VIM+VAR alloy and the EAF+LF+VAR alloy are determined to be 358.15 and 372.54 kJ·mol^-1, respectively. A new dynamic recrystallization model is established by introducing the dynamic recrystallization velocity parameter k_v with critical strain and 50% dynamic recrystallization volume fraction strain. Prasad criterion is used to draw the hot processing maps at 0.2, 0.5 and 0.9 strain of the A286 alloy prepared by the two smelting processes. Combined with the microstructure analysis, the optimal hot working conditions of the VIM+VAR alloy is 1050-1100 ℃, 0.01-1 s^-1 and 1100-1150 ℃, 0.1-10 s^-1, while that of the EAF+LF+VAR alloy is 1050-1100 ℃, 0.01-1 s^-1 and 1100-1150 ℃, 0.1-3 s^-1. It is concluded that the VIM+VAR alloy has a wider hot-working range and its hot-working performance is better than that of the EAF+LF+VAR alloy.