Combined effect of bismuth content and cooling rate on microstructure and mechanical properties of al-8.5Si-0.4Mg-0.3Fe alloy

Abstract

This study investigates the combined effect of Bi content (0.1, 0.2, 0.4 and 0.5 wt.%) and cooling rate (from 0.7 to 4°C/s) on the microstructure, tensile characteristics, quality index and two Weibull modulus of an Al-8.5Si-0.4Mg-0.3Fe alloy. Results show that Bi refined the eutectic Si structure and that increasing the cooling rate intensifies the refining efficiency. The thickness of the β-Al5FeSi intermetallic decreased with an increase in the cooling rate, but no significant effect was observed with the addition of Bi. The contour maps of mechanical properties suggest that the effect of cooling rate on mechanical properties was more significant than that of Bi additions. The highest Weibull modulus for the base alloy and Bi-containing alloy was obtained at the cooling rate of 4°C/s. Decrease in the thickness of β intermetallic phase and reduced porosity with increasing cooling rate appeared to cause a decreased variability of UTS data.