初始显微组织状态对热拉伸变形过程中Al-Zn-Mg-Cu合金流动行为的影响

Effect of Initial Microstructure States on Flow Behavior of Al-Zn-Mg-Cu Alloy During Hot Tensile Deformation

摘要:

为研究Al-Zn-Mg-Cu合金均质态和轧态初始组织对拉伸流动行为的影响，在GLEEBLE-3500等温模拟器上进行温度范围为380~440 ℃、应变率范围为0.05~1 s^-1的等温拉伸试验。建立了Johnson-Cook模型、Hensel-Spittel模型、应变补偿的Arrhenius模型以及临界应变模型。结果表明：通过相关系数R和平均绝对相对误差评估模型，证明应变补偿的Arrhenius模型能更准确地代表合金的流动行为。在均匀化样品中剪切带更为明显，而在轧制样品中动态再结晶则占主导地位。断裂形态分析表明，均匀态试样中混合断裂机制占主导地位，而轧制试样中主要是延性断裂机制。加工图谱显示，与均匀态试样相比，轧态试样的不稳定区域减小，最优热加工窗口分别确定为410~440 ℃/0.14–1.00 s^-1和380~400 ℃/0.05~0.29 s^-1。

Abstract:

To investigate the influence of Al-Zn-Mg-Cu alloy with as-homogenized and as-rolled initial microstructures on the tensile flow behavior, isothermal tensile tests were conducted on a GLEEBLE-3500 isothermal simulator at temperatures of 380–440 °C and strain rates of 0.05–1 s^-1. The Johnson-Cook model, Hensel-Spittel model, strain-compensated Arrhenius model, and critical fracture strain model were established. Results show that through the evaluation of the models using the correlation coefficient (R) and the average absolute relative error, the strain-compensated Arrhenius model can represent the flow behavior of the alloy more accurately. Shear bands are more pronounced in the as-homogenized specimens, whereas dynamic recrystallization is predominantly observed in as-rolled specimens. Fracture morphology analysis reveals that a mixed fracture mechanism is prevalent in the as-homogenized specimen, whereas a ductile fracture mechanism is predominant in the as-rolled specimen. The processing maps indicate that the unstable region is reduced in the as-rolled specimens compared with that in the as-homogenized specimens. The optimal hot working windows for the as-homogenized and as-rolled specimens are determined as 410–440 °C/0.14–1 s^-1 and 380–400 °C/0.05–0.29 s^-1, respectively.