Effect of eutectic Si size on the flow behavior and hot processing map of near eutectic Al-Si alloys

Flow behavior of three near eutectic Al-Si alloys with the same chemical composition but different average eutectic Si sizes (A1, 1.7 mu m; A2, 4.4 mu m; A3, 8.2 mu m) was investigated by isothermal compression tests conducted on a Gleeble-3500 thermal simulator under four different temperatures (350 degrees C, 400 degrees C, 450 degrees C, and 500 degrees C) and four different strain rates (0.01 s(-1), 0.1 s(-1), 1 s(-1), and 5 s(-1)), with a focus on the effect of eutectic Si size. Not only the flow behavior but also the processing map of near eutectic Al-Si alloys are affected by eutectic Si size. The overall trends of the flow stress-strain curves of the three alloys are similar, but their steady flow stresses a s are different: A1 alloy has the largest sigma(s), followed by that of A3. Strain-compensated constitutive equations in the hyperbolic sine form were constructed to describe the flow stress behavior of the three alloys. Materials constants of the constitutive equations depend on eutectic Si size. The processing maps of the three alloys exhibit different characteristics. The instability domain of A2 alloy is restricted to strain rates larger than about 0.4 s(-1), in contrast to the case of A1 and A3 alloys in which the instability domain occurs at both low and high strain rates. The results presented in this study indicate that eutectic Si size is an indispensable factor to be considered when dealing with the hot working of Al-Si alloys. (C) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

The flow behavior of three near eutectic Al-Si alloys with different average eutectic Si sizes was investigated by isothermal compression tests. It was found that the eutectic Si size affects not only the flow behavior but also the processing map of the alloys. The strain-compensated constitutive equations depend on eutectic Si size and the processing maps of the alloys exhibit different characteristics.