过共晶Al-Si合金半固态触变成形本构方程

通过对过共晶Al-20Si-3Fe-1Mn-4Cu-1Mg合金进行半固态单向压缩热模拟试验，研究变形温度为833 K、853 K 、873 K，应变速率为0.1 s–1、0.01 s–1、0.001 s–1的半固态触变成形行为。试验结果表明，变形抗力随变形温度的升高而降低，随应变速率的增加而增大。对试验得到的真实应力应变曲线进行分析，提出将不同真应变范围的半固态触变成形过程划分为类弹性变形、应变硬化和流变-黏塑性变形阶段的新方法，并分阶段建立半固态触变本构方程，采用多元回归得到各阶段的本构方程表达式。所建半固态触变本构方程与试验曲线的比较结果表明，大多数相关系数均在0.95以上，相伴概率均小于0.001，说明根据所建本构方程计算得到的真应力-真应变曲线与试验曲线吻合良好，所建本构方程有意义且具有较高的精度，能够体现出该合金半固态触变过程变形行为，可以将其应用于过共晶Al-20Si-3Fe-1Mn-4Cu-1Mg合金半固态触变成形过程的数值模拟。

Semi-solid Thixoforming Constitutive Equation of Hypereutectic Al-Si Alloy

The semi-solid thixoforming behavior of hypereutectic Al-20Si-3Fe-1Mn-4Cu-1Mg alloy is studied by single-pass compression experiment, at a range of deformation temperature of 833 K, 853 K, 873 K and a range of strain rate of 0.1 s–1, 0.01 s–1, 0.001 s–1. The results show that the flow stress is decreased with increasing in deformation temperature and it is increased with increasing in strain rate. A new method is discussed that semi-solid thixoforming can be divided into analogous elastic deformation, strain hardening and rheology-viscoplastic deformation stages in different true strain range. The thixoforming constitutive equations are derived by multiple regressions in different deformation stage. The curves are calculated by the thixoforming constitutive equations compared with the experiment curves show that the thixoforming constitutive equations have higher precision and fit well with the experimental curves, for most correlation coefficients are above 0.95, and concomitant probabilities are less than 0.001. The true stress-strain development regularity and characteristics can be reflected by the semi-solid thixoforming constitutive equations, it can be applied in the simulation of semi-solid thixoforming process of hypereutectic Al-20Si-3Fe-1Mn-4Cu-1Mg alloy.