5A90Al-Li合金超塑性变形过程中的显微组织及微观织构演变

通过采用电子背散射衍射技术研究具有扁平状组织的5A90 Al-Li合金板材在变形条件475℃、8×10^-4S^-1时的显微组织演变。结果表明，在进行超塑性变形前，其显微组织表现为扁平状组织，具有大量的小角度晶界，且初始板材具有明显的黄铜织构{110}（112）。在变形过程中发生了晶粒的长大、晶粒形貌的改变、晶粒取向差的增大以及织构的弱化，而且大角度晶界的含量在流动应力到达最大值后开始逐渐增加。同时，对不同阶段的相关变形机制进行了讨论。超塑性变形初始阶段的主要变形机制为位错运动，随着变形的进行而开始发生动态再结晶，晶粒旋转作为晶界滑移的主要协调机制。在超塑性拉伸的最后大应变阶段，晶界滑移是主要的变形机制。

Grain structure and microtexture evolution during superplastic deformation of 5A90 Al-Li alloy

The microstructural evolution of banded 5A90 A1-Li alloy during superplastic deformation at 475℃ with an initial strain rate of 8× 10^-4 S^-1 was studied using EBSD technique. The results showed that, before deformation, the grain shape appeared to be banded, the most grain boundaries belonged to low-angle boundaries, and the initial sheet had a dominate of { 110}（112） brass texture. During deformation, there were grain growth, grain shape change, misorientation increasing and textural weakening. The fraction of high-angle boundaries increased rapidly once the flow stress reached the peak value. Corresponding deformation mechanism for various stages of deformation was suggested. Dislocation activity was the dominant mechanism in the first stage, then dynamic recrystallization occurred, and grain rotation was expected as an accommodation for grain boundary sliding （GBS）. At large strains, GBS was the main mechanism.