纯镍多晶体循环形变过程中位错结构的TEM研究

TEM Study on Dislocation Microstructure in Cyclic Deformation of Ni Polycrystal

本文对纯镍多晶体循环形变过程中位错结构,特别是驻留滑移带(PSB)的形成及特性进行了TEM研究,并用选区电子衍射确定了晶粒膜面及其它晶体学取向。结果表明在循环饱和的开始点附近已观察到以梯状花样为特征的PSB;证明循环硬化阶段的末端基本上与PSB的成核相对应。并证实PSB结构是一种体效应。

The dislocation microstructure and, in particular, the formation of persistent slipbands(PSBs)as well as their characteristics of in the cyclic deformation of Ni polycrystal were studied by transmission electron microscopy (TEM).The crystallographic orientation of grains observed and PSBs were determined by the selected area diffraction pattern.The experimental results showed that near the starting point of cyclic saturation stage (N=1800) was found a ladder_like pattern similar to PSB in copper, which suggested that the end of the cyclic hardening stage corresponded largely to the nucleation of PSB.The PSB structure in the fatigued Ni polycrystal was a bulk phenomenon.The grain boundaries of the polycrystal were effective obstacles for PSB propagation and twin helped to nucleate the PSB.The PSBs terminated On grain boundaries or tapered away after they formed porpagated in the grain.ln addition to parallel PSBs on the primary slip system, PSB on the secondary slip system could also be seen in some grains favourably orientated for multiple slip.The dislocation microstructure and the formation and evolution of PSBs in the interior of fatigued Ni polycrystal were in agreement with the results osberved in fatigued Cu polycrystal