( 1. 福建农林大学 机电工程系， 福州 350002;
2. 北京理工大学 应用力学系， 北京 100081)
摘 要: 基于γ-基多孪晶晶体微结构及滑移系和形变孪晶空间晶体学位向分布的变形机制，提出了分析晶体屈服应力对外载轴和片层界面夹角间的依赖关系及影响因素的细观力学解析模型。 分析了α2相中柱面和锥面上滑移系的启动对多孪晶晶体屈服应力的影响。模拟计算和分析结果表明： 当θ=0°时， 位错滑移方向跨越片层界面， α2相中柱面滑移系开动； 当θ=45°时， 滑移方向平行片层界面；当θ=90°方向时, γ相中与片层界面斜交的孪晶开动，而α2相中锥面滑移系由于其临界剪切应力(CRSS)很大而并不开动。多孪晶晶体中孪晶与普通位错、 柱面与孪晶及锥面与柱面之间的CRSS比值关系可确定为k∶e∶z=1∶3∶18。
关键字: γ-基合金； 多孪晶晶体； 滑移系； 屈服应力； 细观力学
（ 1. Department of Mechanics-electrics Engineering,
Fujian Agriculture and Forestry University, Fuzhou 350002, China;
2. Department of Applied Mechanics,
Beijing Institute of Technology, Beijing 100081, China）
Abstract: An analytical micromechanical method, based on the lamellar microstructure, dislocation slip and twinning deformation mechanisms of polysynthetically twinned crystal (PST), was proposed to investigate the yielding stress change as function of loading angle(θ) between the load axis and the lamellar boundaries and some influence paramelers for a PST crystal. The effects of prism and pyramidal slip systems in α2 lamellars on the yield stress of polysynthetically twin crystals of TiAl were analyzed. The simulation and analyses results indicate that, when θ=0°, the slip is activited to cross the lamellar boundaries and the prism systems in α2 phase are activited. When θ=45°, the slip occurs parallel to interlamellar boundaries. When θ=90°, the twinning in γ phase are actived to cross the lamellar boundaries and the pyramidal slip systems in α2 phase are not actived due to much higher critical resolved shear stress on the pyramidal planes. The rate of critical shear stress (CRSS) for twinning to ordinary slip, prism to twinning and pyramidal to prism can be described as k∶e∶z=1∶3∶18.
Key words: γ-alloys； polysynthetically twinning crystal； slip system； yield stress； micromechanics
