材料期刊网

基于γ-TiAl基PST晶体的微结构及滑移系和形变孪晶的空间晶体学位向分布的变形机制, 提出了分析PST晶体屈服应力对外载轴和片层界面夹角θ间的依赖关系的细观力学解析模型, 重点考察了PST晶体的微结构和普通位错与形变孪晶的临界分切应力(CRSS)之间的差别对晶体屈服的影响. 结果表明: PST晶体屈服应力σy和外载轴与片层界面之间的夹角θ存在着强烈依赖关系. 在软取向, 变形由普通位错和超位错控制, 变形平行于片层界面; 而在硬取向, 变形由形变孪晶控制, PST晶体的变形为穿过片层界面形式. 在加载角分别为45°, 0°和90°时, 屈服应力间的关系为: σy (45°)<σy (0°)<σy (90°). 同时, 分析了滑移系和形变孪晶的具体开动情况.

An analytical micromechanical method, based on the lamellar microstructure and dislocation slip and twinning deformation mechanisms of polysynthetically twinning (PST) crystal, is used to investigate the variation of the yielding stress as function of angle θ between the load axis and the lamellar boundaries for a PST crystal. The sub-domain microstructure of the γ-TiAl-based alloy, PST crystal , slip system phase in PST crystal and the difference of CRSS in ordinary slip and true twinning have been considered in this paper. The results demonstrated that yielding stress relations on loading angle with respect to the microstructure and in soft mode of deformation, which is determined by ordinary dislocation or superdislocation slip systems in γ phase, shear deformation is parallel to the lamellar boundaries; in hard mode of deformation, shear deformation crosses the lamellar boundaries, which is controlled by twinning in the γ phase. In addition, the predicted yield stress values of PST crystals for three loading angles θ=45°, 0°and 90°have the relation as σy(45°)<σy(0°)}<σy(90°). Furthermore, the active slip and twinning systems have also been analyzed systematically.