(中国科学院 金属研究所，沈阳 110016)
摘 要: 研究γ-TiAl基合金在温度低于α相转变温度(tα−10)时挤压过程中的组织演变。结果表明：在初始变形阶段，片层发生扭折，随着应变量和应变速率的增大，扭折处发生动态再结晶，形成细小的晶粒；而残余片层随着应变量的增大，其垂直流线方向横断面的尺寸逐渐减小，体积分数也逐渐减少，但其沿流线方向尺寸没有明显减小，残余片层界面方向随着受力状态的变化而变化，其法向平行于主应力方向；经过挤压加工的试样，其边缘片层接近完全破碎，而中心残余片层尺寸较大；挤压坯料与模具的摩擦作用与热传导严重影响了全片层晶粒的破碎细化，温度场以及变形的不均匀是造成材料不同部位微观组织差异的重要因素。
关键字: γ-TiAl基合金；热挤压；组织演变；残余片层
（Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China）
Abstract:The microstructure evolution of γ-TiAl alloy extruded at temperature below α phase transition temperature (tα−10) was investigated. The results show that the lamellar structure kinks at initial deformation stage with increasing strain and strain rate, the region undergoes dynamic recrystallization and forms fine crystal zone and shear localization zone. The size perpendicular to flow line and volume fraction of remnant lamellar are reduced at higher strain, but the size along flow line is not reduced. The direction of remnant lamellar boundary is changed with changing stress state. The phase boundary between Ti3Al and γ-TiAl parallels to flow line. The lamellar of sample at the edge fabricated by extrusion has almost completely broken down, but the remnant lamellar size is large at the central region, especially at the longitudinal section. Friction and heat transfer between the perform and die have great influence on the refinement of full lamellar grain. The heterogeneity of temperature and strain are responsible to the difference of microstructure.
Key words: γ-TiAl based alloy; hot extrusion; microstructure evolution; remnant lamellar structure
