(1. 湖南科技大学 高功效轻合金构件成形技术及耐损伤性能评价湖南省工程研究中心，湘潭 411201；
2. 宁波大学 机械工程与力学学院，宁波 315211；
3. 湖南工学院 汽车零部件技术研究院，衡阳 421002)
摘 要: 对铸态AZ31镁合金进行温度300~400 ℃、平均应变速率5.4~29 s-1的高应变速率轧制，制备不同孪晶和晶粒尺寸分布的镁合金板材，研究孪晶及晶粒尺寸分布对镁合金高应变速率轧制板材强韧化的影响，并建立了多尺度组织的强韧化模型。结果表明：平均应变速率低于10 s-1时，可以获得孪晶、细晶和粗晶共存的多尺度组织，且平均应变速率为8.3 s-1时，组织中存在大量的亚微晶；在室温变形过程中，不同尺度组织之间的背应力能够保证材料塑性，孪晶界和细晶保证强度，实现亚微晶、细晶、孪晶和粗晶共存的多尺度组织镁合金具有高的抗拉强度，同时能够保持相对良好的伸长率；在高温变形过程中，亚微晶、细晶、孪晶和粗晶共存的多尺度组织镁合金中的亚微晶发生晶界滑动、粗晶和孪晶诱导再结晶提高了材料塑性；温度为300 ℃变形时，强度亦遵循Hall-Patch公式。
关键字: AZ31镁合金；多尺度组织；亚微晶；孪晶；背应力
（1. Hunan Engineering Research Center of Forming Technology and Damage Resistance Evaluation for High Efficiency Light Alloy Components, Hunan University of Science and Technology, Xiangtan 411201, China;
2. Faculty of Mechanical Engineering and Mechanics, Ningbo University, Ningbo 315211, China;
3. Research Institute of Automobile Parts Technology, Hunan Institute of Technology, Hengyang 421002, China）
Abstract:Aiming to produce magnesium alloy sheets with different distributions of twin and grain size, the high-strain rate rolling was carried out on as-casting AZ31 magnesium alloys at temperatures of 300-400 ℃ and average strain rates of 5.4-29 s-1. The effects of twin and grain size distribution on the strengthening and toughening of high-strain rate rolled magnesium alloy sheets were studied. The strengthening and toughening model was also established. The results show that when the strain rate is lower than 10 s-1, the multi-scale microstructure including twin, fine grain and coarsen grain can be obtained and majority submicro-grains appear at an average strain rate of 8.3 s-1. During room temperature deformation, the back stress between different scale grains leads to good plasticity, and the twin boundaries and fine grains result in high strengthen. Then, high strengthen and relatively good plasticity are obtained in magnesium alloy with multi-scale microstructure including submicro-grain, fine grain, twin and coarsen grain. During high temperature deformation, the occurrence of grain slide in submicorgrain, the onset of dynamic recrystallization inside coarsen grains and twin induced dynamic recrystallization cause the plasticity improvement in magnesium alloy with multi-scale microstructure including submicro-grain, fine grain, twin and coarsen grain. At a deformation temperature of 300 ℃, the strengthen still obeys the Hall-Patch equation.
Key words: AZ31 magneisum alloy; multi-scale microstructure; submicrograin; twin; back stress
