热变形对汽车用Al-Sc-Zr合金高温流变形行为的影响及本构方程的建立

Influence of thermal deformation on deformation behavior of high-temperature flow of Al-Sc-Zr alloy for automobiles and establishment of constitutive equations

在Gleeble-3000D热模拟机上对Al-0.2Sc-0.04Zr铝合金开展了热变形实验,系统地研究该合金变形参数在0.001~5 s^(-1)和440~600℃下的高温流变行为。研究结果表明:在低应变速率和较高的温度下,DRX的发生较为完全。同时,在较低温度(T≤520℃)下变形,主要软化机制为动态回复;在较高温度(T>520℃)下变形,软化机制转变为动态再结晶,且获得了较为完全的动态再结晶组织;在高温(T≥600℃)下变形,晶粒出现明显的长大。分析应力指数(n)和变形激活能(Q),二者均随变形温度的升高而增加。采用双曲正弦模型,建立了适合Al-0.2Sc-0.04Zr合金的本构方程,可很好地预测峰值应力,为工业化生产提供理论依据。

A one-way thermal compression experiment of Al-0.2Sc-0.04Zr aluminum alloy on the Gleeble-3000D thermal simulator was conducted to study the thermal deformation behavior under the strain rate of 0.001~5 s^(-1) and a thermal deformation teperature of 440~600℃.The results show that the degree of dynamic recrystallization increases with increasing deformation temperature or decreasing strain rate.Meanwhile,for deformation at lower temperatures(T≤520℃),the main softening mechanism is dynamic recovery,and for deformation at higher temperatures(T>520℃),the softening mechanism changed to a dynamic recrystallization softening mechanism,obtaining a relatively complete dynamic recrystallization structure.Deformed at high temperatures(T≥600℃),the grains grow significantly.By analyzing the stress index and the deformation activation energy,the stress index(n)increases with increasing deformation temperature.The deformation activation energy(Q)increases with increasing deformation temperature and strain rate within the range of experimental temperatures.The peak stress of the Al-0.2Sc-0.04Zr alloy was analyzed by the hyperbolic-sine Arrhenius constitutive equation,and the average absolute relative error(AARE)between the predicted value and measured value of the alloy is only 7.428%as well as the correlation coefficient(R)0.9708.