含微量稀土元素的Al-Zn-Mg合金的超塑变形机制

SUPERPLASTIC MECHANISM OF Al-Zn-Mg ALLOYS CONTAINING SMALL AMOUNTS RARE-EARTHS

用透射电镜详细观察了含微量稀土的 Al-Zn-Mg 合金在超塑变形过程中晶界位错的形态、运动及其与晶界第二相粒子的相互作用情况。发现晶界中的第二相粒子对位错沿晶界运动有明显的阻碍作用。实验还发现在含第二相粒子较多的晶界的超塑性合金中,晶界滑动是通过位错沿晶界运动和晶界的粘滞性流动两种机制同时发生作用进行的,它们相互促进并共同推动了晶界滑动的发展。首次在透射电镜下观察到超塑变形使晶界加宽的现象,在面缩率ψ=72.2%的样品中测得某晶界的宽度约为100nm,从而证实了超塑变形的晶界滑动和晶粒转动机制。

The configurations and the motions of grain boundary dislocations(GBD)andthe interations of the GBD with the precipatation particles in the grain boundary(GB)were ob-served with the TEM.It was found that the motions of the GBD along the GB can be hinderedby the precipatation particles.We considered that the GB sliding in the superplastic alloys withthe more precipatation particles in GB was caused by the two kinds of mechanism-the disloca-tions moving along the GB and the viscous flow of the GB.The phenomena of GB widen in thealloys after superplastic deformation were observed with the TEM,the GB′S width is about100nm.It indirectly proved that the mechanism of superplasticity is GB sliding and grain rotion.