Mg-7.0Al-0.2Zn合金的超塑性及其变形机制

Superplasticity and Deformation Mechanism of Mg-7.0Al-0.2Zn Alloys

摘要:

研究不具有典型细晶组织的挤压态Mg-7.0Al-0.2Zn（AZ70）合金的超塑性及其变形机制。结果表明：AZ70镁合金具有良好的超塑性变形行为。在380 ℃及1×10-3 s-1的最佳变形条件下，最大伸长率为191.5%。380 ℃时具有良好的高应变速率（1×10-2 s-1）超塑性变形能力，伸长率为161.5%。晶粒尺寸随温度的升高与应变速率的降低而增大。超塑性变形是以晶界滑移为主，表现为变形过程中晶粒组织基本保持等轴，且孔洞沿晶界形成并长大。同时孔洞的长大及连接导致最终断裂，断口形貌显示为典型的韧窝断裂特征

Abstract:

Superplasticity and deformation mechanism of Mg-7.0Al-0.2Zn（AZ70）alloys without typical fine-grained structure was investigated. It is indicated that the AZ70 alloy exhibits superior superplasticity and the maximum elongation of 191.5% was obtained at 380 ℃ and 1×10-3 s-1. It is worth mentioned that high-strain-rate (＝1×10-2 s-1) superplasticity with elongation of 161.5% was achieved at 380 ℃. The mean grain sizes increase with temperature increasing and strain rate decreasing. The grain boundary sliding (GBS) is the dominant deformation mode of the superplasticity, which is verified by grains remaining equiaxial during deformation. Cavities form and grow up along grain boundary. And then the growth and connection of cavities results in the final failure. SEM morphology of the failure surface shows typical tenacity failure characteristics with quantities of uniform dimples.