铜三晶体的循环形变行为及位错组态

CYCLIC DEFORMATION BEHMIORS AND DISLOCATION STRUCTURES OF COPPER TRICRYSTALS

采用逐级增幅方法研究了［００１］同轴钢三晶体及一种非同轴取向平行三晶交线铜三晶体的循环形变行为，并观察了三晶交点和晶界附近的位错组态为了对比，也研究了两种取向三晶体的组元晶粒双晶体和单晶体试样的循环形变行为对于［００１］同轴取向平行三晶交线三晶体及其组元双晶体和单晶体，其循环硬化曲线几乎重合，其循环饱和应力应变曲线（ＣＳＳＣ）也相差不大，由于各滑移系之间的位错反应生成Ｌｏｍｅｒ－Ｃｏｔｔｒｅｌ锁，阻碍位错运动，所以三晶交线和晶界对轴向饱和应力几乎没有强化作用，对于［００１］取向晶体，在（００１）观察面上，可以看到很多较短的一段一段的位错墙结构，各段之间互不连通，这是各滑移系之间的位错反应强烈，生成不动的位错锁的结果，这也是三晶交线和晶界无明显强化作用的原因，对于非同轴取向钢三晶体及组元晶粒双晶体、单晶体的循环形变行为研究表明，只要是相同取向的晶粒，不论是单晶体、双晶体还是三晶体，位错组态基本相同，相同的位错组态对应相同的轴向应力，双晶体和三晶体的轴向饱和应力主要由各晶粒所占的体积分数决定，稍高于各晶粒轴向饱和应力按体积分数的加权平均对于非同轴三晶体和双晶体，在相同的应变幅下，相同的观察面和相同的晶界附近，滑?

Cyclic deformation behaviors of [001] isoaxial copper tricrystal, one nonisoaxial tricrystal as well as bicrystals and single crystal were studied. It was found that the cyclic hardening curves of [001] tricrystal, bicrystals and single crystal were almost overlapped at initial rapid hardening period, the difference between them was not obvious even at the saturation period. Cyclic stress-strain (CSS) curves of bicrystals were slightly higher than that of single crystal, the CSS curve of tricrystal located between them. There were no effect zones in the vicinity of grain boundaries and triple junction by the observation of dislocation microstructures. The strengthening effects of grain boundaries and triple junction lines on axial stress of specimens were almost negligible owing to the formation of Lomer- Cottrell locks caused by the reaction of dislocations on different slip planes. For nonisoaxial tricrystal and its component bicrystals and monocrystals, dislocation patterns in tricrystal and bicrystals are similar to that in component single crystals, and the axial saturation stresses of tricrystal and bicrystals are mainly due to the volume fractions and axial stress of its component single grains, they are only a littte greater than volume fraction weighted average. For isoaxial and nonisoaxial tricrystal and bicrystals, slip morphologies near the same GB are almost the same at the same strain amplitudes.