Influence of Mold and Pouring Temperatures on Hot Tearing Susceptibility of AZ91D Magnesium Alloy

This research focused primarily on studying the effect of mold temperature on the hot tearing susceptibility of permanent mold cast (PMC) AZ91D magnesium alloy. The results suggest that increasing the mold temperature from 140 °C (282 F) to 380 °C (716 F) had a significant impact on the severity of hot tearing in the alloy. Mold temperatures above 340 °C (644 F) were seen to virtually eliminate hot tears through a morphological change of the alloy’s β-phase regions, which enabled liquid metal feeding of the casting at later stages of solidification and high fractions of solid. Variation of the mold temperature also affected the alloy yield strength and casting porosity. The effect of increasing the pouring temperature in the 680–720 °C (1256–1328 F) range to reduce hot tearing was less pronounced than that of varying the mold temperature.