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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1×10-3s-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(1×10-2s-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。
The superplasticity and deformation mechanism of as-extruded Mg-7.0Al-0.2Zn (AZ70) alloys without typical fine-grained microstructure were investigated. The results show that AZ70 magnesium alloy has good superplastic deformation behavior. Under the optimum deformation conditions of 380 ℃ and 1 × 10-3s-1, the maximum elongation was 191.5%. 380 ℃ has a good high strain rate (1 × 10-2s-1) superplastic deformation capacity, elongation of 161.5%. The grain size increases with increasing temperature and decreasing strain rate. Superplastic deformation is based on grain boundary slip, the performance of the deformation of the grain structure to maintain the basic equiaxed, and the hole along the grain boundary formation and growth. At the same time, the growth and connection of the holes resulted in the final fracture, and the fracture morphology showed typical dimple fracture characteristics.