(1. 湖南科技大学 材料科学与工程学院，湘潭 411201；
2. 湖南科技大学 机电工程学院，湘潭 411201)
摘 要: 为了研究高速冲击载荷下预变形AZ31镁合金的高温流变行为和组织演变过程以及构建能够准确预测高温流变行为的本构模型，采用霍普金森压杆技术，对预变形AZ31镁合金进行应变速率分别为2150 s-1、3430 s-1、4160 s-1，变形温度分别为150 ℃、200 ℃、250 ℃、300 ℃、350 ℃的高温冲击试验。结果表明：在相同应变速率下某些温度区间内，由于孪晶强化、细晶强化和升温软化三者共同作用，流变应力出现随温度升高下降幅度不明显的现象；随着变形温度的升高，其组织呈现交叉孪晶、变形剪切带、转变剪切带、完全再结晶的转变；引入孪晶强化项修正Johnson-Cook本构模型，修正后的Johnson-Cook本构模型可以准确地预测出孪晶对流变行为的影响，同时通过计算得到相关系数(R)为0.9744，平均相对误差(E)为4.51%，表明所修正的模型能够较好地描述预变形AZ31镁合金的高温流变行为。
关键字: AZ31镁合金；高速冲击；孪晶；流变行为；Johnson-Cook本构模型
（1. School of Materials Science and Engineering, Hunan University of Science and Technology, Xiangtan 411201, China;
2. School of Mechanical Engineering, Hunan University of Science and Technology, Xiangtan 411201, China）
Abstract:In order to investigate the high-temperature flow behavior and microstructure evolution of the pre-deformed AZ31 magnesium alloy under high-speed impact loading and establish a constitutive model to accurately predict the high-temperature flow behavior, high-temperature impact tests at deformation temperatures of 150 ℃, 200 ℃, 250 ℃, 300 ℃, and 350 ℃ with strain rates of 2150 s-1, 3430 s-1, and 4160 s-1 were carried out on the pre-deformed AZ31 magnesium alloys using the Hopkinson pressure bar technology. The results show that, under certain temperature range with the same strain rate, due to the effects of twin strengthening, fine grain strengthening and heating softening, the flow stresses do not obviously decrease with increasing the temperature. With the increase of deformation temperature, the microstructures transform from cross twinning, deformed shear bands, transition shear bands to complete recrystallization. The twinning strengthening is introduced to modify the Johnson-Cook constitutive model. The modified Johnson-Cook constitutive model can accurately predict the effect of twinning on the flow behavior. The correlation coefficient (R) is 0.9744 and the average relative error (AARE) is 4.51%, indicating that the modified Johnson-Cook constitutive model can well forecast the high-temperature flow behavior of the pre-deformed AZ31 magnesium alloy.
Key words: AZ31 magnesium alloy; high-speed impact; twinning; flow behavior; Johnson-Cook constitutive model
