Effect of Strontium and Misch Metal on Al–14Si–3Mg Alloy

Abstract

The individual and combined effect of Strontium and Misch metal on microstructure and properties of Al–14Si–3Mg alloy was investigated. Addition of 3 wt% Mg to Al–14Si alloy resulted in microstructure comprising of α-Al and ternary eutectic (α-Al, Si and Mg2Si). It was found that Strontium and Misch metal behaved differently when added to Al–14Si–3Mg alloy resulting in significantly different microstructure. While addition of only strontium did not show formation of any new phase having any deleterious effect on microstructure and hardness, the addition of only misch metal though, led to the appearance of rare earth rich phases with branched morphology resulting in decrease in hardness. Also, it was concluded that misch metal in conjunction with strontium yielded best results in terms of microstructure and hardness. The microhardness measurements showed that ternary eutectic region was 1.4–1.7 times harder than the binary eutectic region. Furthermore, the T6 treated Al–14Si–3Mg alloy containing Strontium and Misch metal led to a substantial increase in hardness which was superior to some commercially available Al–Si alloys. Also, differential scanning calorimetry studies were carried out to determine the freezing range of the alloys and assess their feasibility for semisolid processing.