晶内位错在8090铝锂合金超塑性变形中的作用

Effect of Interior Dislocation on Superplastic Deformation of 8090 Al--Li Alloy

研究了 8090 合金超塑性变形中的位错行为。透射电镜观察表明晶内位错产生于三角晶界,晶界台阶和粒子处。在变形初期,晶内位错滑移相当活跃;在变形中期,晶内位错发生回复形成亚晶界;至变形末期,虽然位错回复过程没有停止,但位错滑移协调机制变得更重要了,研究指出,位错滑移是变形初期的主要变形机制。动态回复和位错滑移都是晶界滑动的协调机制。而且,螺型位错与空位交互作用形成不能滑动的卷位错提高了晶内畸变能,促进了动态再结晶。

Dislocation behavior in the superplastic deformation of 8090 Al-Li alloy was investigated.It is indicated by TEM that the interior dislocationis formed just at the triple junction of grain boundary, boundary ledge andparticles. The slip of interior dislocation is quite active at the initial stage ofdeformation and, at the middle stage, the dynamic recovery of interior disloca-tion takes place to form subgrain boundary. Finally, although the dynamicrecovery does not stop up to failure, the accomodation mechanism by disloca-tion slip becomes more important.It is found that dislocation slip is the mainmechanism of deformation at the early stage and the dynamic recovery and dis-location slip are both the accomodation mechanism of grain boundary slidingin superplastic deformation process. In addition,the interaction between screwdislocation and vacancy not only creates helix dislocation unable to slip butincreases distorted lattice energy to promote dynamic recrystallization.