Microstructure and Mechanical Properties of Cast Al-15Mg2Si-8Si-Based Alloy with Various Cr-Sb Ratio Addition

In this study, the effect of adding different proportions of Cr-Sb composite modifiers to a cast Al-15Mg(2)Si-8Si alloy on its microstructure and mechanical properties was investigated. The results show that the addition of 0.5 wt.% Cr-Sb (with a Cr-Sb ratio of 3:7) to the base alloy significantly refines the average SDAS value of alpha-Al and the average size of primary Mg2Si to 10.61 mu m and 13.87 mu m, respectively. Additionally, the mechanism of microstructure refinement and modification is systematically explored. The addition of Cr-Sb promotes the formation of Mg3Sb2 and Al13Cr4Si4 phases by precipitation, forming dendritic or flaky precipitates. As a result of grain refinement and precipitation strengthening, the yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) of the modified alloy were 109, 191 MPa, and 3.2%, respectively, which were 17.9, 58.4, and 12.5% higher than those of the base alloy. It is concluded that the formed Mg3Sb2 particles can act as a nucleation core for the Mg2Si phase to refine the primary phase during solidification, while the Al13Cr4Si4 phase becomes a heterogeneous nucleation core for the eutectic phase, reducing the elongated needle-like eutectic phase. [GRAPHICS] .