Effect of different casting techniques on the microstructure and mechanical properties of AE44-2 magnesium alloy

Abstract

AE44-2 magnesium (Mg) alloys were fabricated by gravity casting (GC), high pressure die casting (HPDC), and high vacuum assisted high pressure die casting (HVHPDC). The effect of these three different casting techniques on the microstructure evolution, texture, and mechanical properties of the AE44-2 alloy was investigated. The results showed that the different cooling rates in these three different casting techniques led to the different distribution and morphology of the precipitated phases, and rapid cooling contributed to a dense network distribution of the phases as well as grain refinement. In addition, the faster cooling rate resulted in a decrease of the dislocation accumulation. The addition of vacuum assistance in the HPDC process increased texture strength. The average grain size of the HPDC alloy was reduced by 90.4% compared to the GC alloy and the yield strength increased by 85.7 MPa due to rapid cooling. The elongation of the HVHPDC alloy increased by 2.3% compared to the HPDC alloy due to vacuum assistance. Moreover, the mechanical properties improved for the alloys in the order of GC < HPDC < HVHPDC because of gran refinement caused by the faster cooling rate. Based on the analysis of the strengthening mechanisms, the rapid cooling process of the HPDC alloy led to better strengthening compared to the GC alloy. In addition, grain refinement contributed to 82.1% of the strengthening mechanism.