7475铝合金超塑变形中的显微结构变化

Microstructural Changes of Aluminum Alloy 7475 in Superplastic Deformation

对质点强化型的高强度7475铝合金超塑变形中显微组织变化进行了研究。结果表明,在超塑变形中发生下面三个连续过程:(1)位错从晶界发出;(2)位错攀移越过晶内弥散分布的第二相质点;(3)位错消失于晶界。位错密度随应变的增加而增加。位错攀移越过弥散质点的过程是合金超塑变形的速控过程,超塑变形的主要机制是晶界滑移伴随晶内位错运动。

The microstructural changes of high-strength aluminum alloy 7475 in the process of superplastic deformation were systematically investigated. The results show that three processes will take place in sequence in superplastic deformation, i.e., (1)dislocations come from grain boundaries; (2) dislocations climb up and over the dispersed particles; (3)dislocations are annihilated in grain boundaries. It is found that the dislocation density increases with strain level, and the process of dislocations' climbing over dispersed particles is just that of controlling strain rate in superplastic deformation. For the alloy, the dominant mechanism of superplastic deformation is that the boundary sliding process will be accompanied by intragranular dislocations.