Abstract: 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.

Key words: constitutive equations, hypereutectic Al-Si alloy, semi-solid processing, thixoforming