铝锂合金超塑性变形模型

A Model of Superplastic Flow in Al-Li Alloys

透射电镜(TEM)观察表明 8090 和 CP276 铝锂合金在超塑性变形最佳条件下,除位错滑移、攀移和扩散蠕变外,还发生贯穿变形始终的动态回复和动态再结晶,研究指出,8090和 CP276 铝锂合金的超塑性变形是位错滑移、在晶界上的位错攀移、三角晶界处阻碍晶粒的动态再结晶及扩散蠕变共同协调晶界滑动的过程,其中,在晶界上的位错攀移及三角晶界处阻碍晶粒的动态再结晶是两个交替作用的速控过程。本文提出了有动态回复和动态再结晶参与协调晶界滑动的超塑性变形复合模型。由该模型解释了 8090 铝锂合金冷、热轧态及 CP276铝锂合金超塑性能的差异。

TEM observations indicated that not only the dislocation slip,dislocation climb and diffusion creep but also accomodate the dynamic recovery and dynamic recrvstallization will take place all through the deformation process under the optimum conditions of superplastic deformation in Al-Li alloys 8090 and CP276. The study also indicated that the superplastic deformation in these alloys is the process dominated by grain boundary sliding which is accomodated by the dislocation slip, dislocation climb at grain boundary together with the dynamic recrystallization of obstructive grains at triple junction of grain boundary and diffusion creep. Among them the dislocation climb at boundary and the dynamic recrystallization of obstructive grains at triple junction of grain boundary are two rapidly controlling processes functioning alternately. A complex model of superplastic deformation in terms of the grain boundary sliding accomodated by both the dynamic recovery and dynamic recrystallization is thus developed. Discrepancies of as-cold-rolled/as hot-rolled superplastic property between Al-Li alloys 8090 and CP276 can be explained by this model.