(1. 西北工业大学 材料学院 凝固技术国家重点实验室，西安 710072；
2. 西北有色金属研究院，西安 710016)
摘 要: 利用Gleeble-3800型热模拟试验机对经过3次真空自耗熔炼的TiAl-3Ta-x(Cr,W)(摩尔分数，%)合金进行了热模拟等温压缩试验，研究在1 150~1 250 ℃及0.01~1 s-1应变速率下的高温流变行为及其微观组织演变。结果表明，在合金的高温变形过程中，曲线呈明显的先硬化后软化的流变行为特征，应变速率的降低或温度的升高都会使合金的流动应力降低；热变形使组织由粗大的铸态γ/α2近片层组织演变为细小的近等轴γ/α2组织。造成该合金流变软化和组织演变的主要原因是片层组织发生了动态再结晶，其最佳高温塑性变形温度为1 200 ℃，应变速率小于1 s-1。
关键字: TiAl基高温合金；高温流变行为；流变软化；本构方程；组织演变
（1. State Key Laboratory of Solidification Processing, School of Materials,
Northwestern Polytechnical University, Xi’an 710072, China;
2. Northwest Institute for Nonferrous Metal Research, Xi’an 710016, China）
Abstract:The samples of TiAl-3Ta-x(Cr,W) (molar fraction, %) were hot compressed by Gleeble-3800 thermal simulation tester. The high temperature flow behavior and microstructure evolution were studied at 1 200-1 300 ℃ and 0.01-1 s-1. The results show that alloy displays a flow characteristic of hardening followed by softening during hot compression. The reduction of the strain rate or the rise of temperature can make flow stress reduce. The microstructure of the alloy evolves from as-cast big size γ/α2 to small size near-equiaxed γ/α2. Dynamic recrystallization (DRX) is the main reason that results in flow softening and micro-structure evolution of the alloy. The optimum temperature for hot forming of cast near lamella the alloy is 1 200 ℃, and the strain rate should be less than 1 s-1.
Key words: TiAl based alloy; high temperature flow behavior; flow softening; constitutive equation; microstructure evolution
