(1. 湖南科技大學 材料科學與工程學院，湘潭 411201；
2. 湖南科技大學 機電工程學院，湘潭 411201)
摘 要: 為了研究高速沖擊載荷下預變形AZ31鎂合金的高溫流變行為和組織演變過程以及構建能夠準確預測高溫流變行為的本構模型，采用霍普金森壓桿技術，對預變形AZ31鎂合金進行應變速率分別為2150 s-1、3430 s-1、4160 s-1，變形溫度分別為150 ℃、200 ℃、250 ℃、300 ℃、350 ℃的高溫沖擊試驗。結果表明：在相同應變速率下某些溫度區(qū)間內(nèi)，由于孿晶強化、細晶強化和升溫軟化三者共同作用，流變應力出現(xiàn)隨溫度升高下降幅度不明顯的現(xiàn)象；隨著變形溫度的升高，其組織呈現(xiàn)交叉孿晶、變形剪切帶、轉(zhuǎn)變剪切帶、完全再結晶的轉(zhuǎn)變；引入孿晶強化項修正Johnson-Cook本構模型，修正后的Johnson-Cook本構模型可以準確地預測出孿晶對流變行為的影響，同時通過計算得到相關系數(shù)(R)為0.9744，平均相對誤差(E)為4.51%，表明所修正的模型能夠較好地描述預變形AZ31鎂合金的高溫流變行為。
關鍵字: AZ31鎂合金；高速沖擊；孿晶；流變行為；Johnson-Cook本構模型
（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
