5A90铝锂合金超塑性变形机理的定量研究

Quantitative study of superplastic deformation mechanism of 5A90 Al-Li alloy

通过聚焦离子束在5A90铝锂合金试样表面蚀刻微米尺寸高分辨网格,在温度480℃、初始变形速率1×10^-3s^-1的变形条件下,定量研究其超塑性变形过程中晶界滑移和晶内位错滑移对总变形的贡献量,并采用扫描电镜、电子背散射衍射观察合金超塑性变形的组织演变作为佐证。结果表明:位错运动在超塑性变形初期(ε<0.65)的贡献量约为60%~80%,为主要变形机制,在该阶段条带状晶粒逐渐细化和等轴化,平均晶粒尺寸减小约40%,晶粒转动作为协调机制;随着应变量的增大,发生明显的动态再结晶,晶粒尺寸开始增大,晶内位错滑移的作用逐渐减小,晶界滑移成为变形的主要机制。

The contribution of grain boundary sliding(GBS) and intragranular dislocation slip(IDS) in the 5 A90 Al-Li alloy during superplastic deformation at 480℃ and an initial strain rate of 1×10^-3s^-1 was quantitatively investigated by analyzing the deformation-induced changes in the sample surface having micron grids etched by focused ion beam. As supporting evidence, scanning electron microscope and electron back scattering diffraction were used to analyze the microstructure evolution during superplastic deformation. The results show that superplasticity is the result primarily contributed by intragranular dislocation slip(about 60%-80%)in the first stage(ε<0.65) and grain rotation is coordination mechanism, with the banded grains refined and equiaxed and the average grain size decreased(about 40%). With the increase of strain, obvious dynamic recrystallization occurs, which gives rise to the increasing grain size, and decreased effect of intragranular dislocation slip, grain boundary sliding gradually becomes the main mechanism.