新型γ­TiAl基合金在高温变形过程中的组织演变

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Ti­44Al­3Ta­0.3(Cr,W)(摩尔分数，%)合金样品进行热模拟等温压缩试验，研究该合金在1150~1250℃及0.01~1 s-1应变速率下高温变形后的宏观与微观组织演变。结果表明，在高温变形过程中，变形使合金中的组织由粗大的铸态γ/α2近片层组织演变为细小的近等轴γ/α2组织。变形过程中原始片层组织发生了不同程度的动态再结晶，动态再结晶是引起组织演变的主要原因。该合金的动态再结晶形核主要由位错塞积和孪晶形核控制。最佳高温塑形变形温度为1200℃，应变速率小于1 s-1。%The samples of Ti­44Al­3Ta­0.3(Cr,W) (mole fraction,%) were hot compressed in the temperature range of 1 200-1 300℃and strain rate range of 0.01-1 s-1 for high temperature flow behavior and microstructure evolution study. The results show that the microstructure of the alloy evolves from as­cast big sizeγ/α2 to small size near­equiaxedγ/α2. The dynamic recrystallization (DRX) is the main reason that origin lamella changes during the hot deformation. The main nucleation mechanism of the DRX is controlled by the twins and the dislocation tangle growth. The optimum temperature for hot forming of the alloy is 1 200℃, and the strain rate is less than 1 s-1.