Effect of Sr on Grain Refinement of Mg-3%Al Alloy Containing Trace Fe by Carbon-Inoculation

Magnesium (Mg)-3% aluminum (Al) (in weight) alloy was modified by carbon (C) inoculation combining with strontium (Sr). The effects of trace 0.1% iron (Fe) addition and operating sequence of carbon-inoculation and Fe addition on the grain size of Mg-3%Al alloy were studied. The results reveal that the Sr addition could effectively suppress grain-coarsening resulted from the inclusion of Fe in the carbon-inoculated Mg-Al alloy. Sr addition could contribute to the formation of the duplex-phase particles that Al-C-rich phases coated on Al-Fe or Al-C-Fe-rich phases, regardless of the Fe addition sequence. These duplex-phase particles should be the potent substrates for α-Mg grains. Consequently, Sr addition could effectively subsidize the inhibiting effect of Fe on grain refinement and the active nuclei were maintained. In other words, Sr plays a counter role in the poisoning effect of Fe on the microstructure of Mg-3%Al alloy.