Al-Mg-Si 合金的高温流变过程动态再结晶研究

采用热力模拟试验机对Al-0.83Mg-0.59Si铝合金进行热压缩实验，研究了变形温度300～500 ℃、变形速率0.001～10 s-1下材料的动态再结晶行为。实验得到Al 0.83Mg 0.59Si合金在300～500 ℃变形时，软化机制以动态再结晶为主；流变应力会随着变形温度的降低和变形速率的升高而升高，较低变形速率下，动态再结晶行为更充分，应力软化现象更明显。统计实验所得流变应力曲线数据，建立了热变形本构方程，确定了合金热变形激活能Q为480.243 kJ/mol 。基于加工硬化率曲线，建立了其动态再结晶临界应变模型。结果表明，Al-0.83Mg-0.59Si铝合金的流变应力随温度的升高和变形速率的降低而降低，动态再结晶是其主要的软化机制。临界应力与峰值应力存在线性关系：σc=0.85σp-5.061 58。引入Zener Hollomon参数来描述变形条件对临界条件的影响，得到临界应变与Z参数的关系为：εc=0.000 134Z0.051 64。

Study on dynamic recrystallization of Al-Mg-Si alloy during high temperature rheological process

The thermal compression experiments of Al 0.83Mg 0.59Si aluminum alloy were carried out with thermal simulator.The dynamic recrystallization behavior of Al 0.83Mg 0.59Si aluminum alloy was studied at deformation temperatures of 300-500 ℃ and deformation rates of 0.001-10 s-1.The experimental results showed that the softening mechanism of Al 0.83Mg 0.59Si alloy was mainly dynamic recrystallization when deformed at 300-500 ℃.The flow stress increased with the decrease of deformation temperature and the increase of strain rate.At lower strain rate,the dynamic recrystallization behavior was more sufficient and the stress softening phenomenon was more obvious.The constitutive equation of hot deformation was established based on the data of rheological stress curve obtained from experiments.The activation energy Q of hot deformation was determined to be 480.243 kJ/mol.Based on the work hardening rate curve,the critical strain model of material dynamic recrystallization was established.The results show that the rheological stress of Al 0.83Mg 0.59Si alloy decreases with the increase of temperature and the decrease of strain rate.Dynamic recrystallization was the main softening mechanism.There was a linear relationship between critical stress and peak stress:σc=0.85σp-5.061 58.Zener Hollomon parameters were introduced to describe the effect of deformation conditions on the critical conditions.The relationship between critical strain and Z parameters was obtained:εc=0000 134Z0.051 64.