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微细晶粒超硬铝LC9合金在470～530℃温度范围内,速率为8.33×10~(-4)～1.66×10~(-2)s~(-1)条件下拉伸呈显出良好的超塑性。在最佳超塑性条件下(T=515℃,ε=1.66×10~(-3)s~(-1))获得延伸率δ=1300％、流变应力δ=1.7MN/M~2应变速率敏感性指数m=0.66 金相和电镜观察表明,在超塑流变过程中,除发生晶界滑动,扩散蠕变外,还发生明显的动态再结晶以及晶内结晶学滑移,晶内位错密度随变形量增大而增加。扩散蠕变导致在横向晶界上形成新的条带区,出现晶界迁移和无沉淀区,同时存在晶内和晶界扩散。空洞在三角晶界处萌生,沿横向晶界方向的扩展连结,导致突然断裂。
The fine grained superhard aluminum alloy LC9 showed good elongation at the temperature range of 470 ~ 530 ℃ and the rate of 8.33 × 10 -4 ~ 1.66 × 10 -2 s -1 Superplasticity The elongation δ = 1300% and the flow stress δ = 1.7 MN / M ~ 2 were obtained under the optimal superplastic condition (T = 515 ℃, ε = 1.66 × 10 -3 s -1) Rate sensitivity index m = 0.66 Metallographic and electron microscopic observations show that in addition to grain boundary sliding and diffusion creep, significant dynamic recrystallization and intracrystalline crystallographic slip occur during the superplastic rheological process. Dislocation density increases with the increase of deformation. Diffusion creep results in the formation of new banding regions on the lateral grain boundaries, grain boundary migration and non-precipitation areas, with simultaneous intragranular and grain boundary diffusion. Voids initiate at the triangular grain boundaries and extend along the lateral grain boundaries, resulting in sudden fracture.