Abstract:
The effect of iron on the grain refinement of Mg-Al alloys prepared from high purity Mg and Al ingots was investigated. Various iron additions were made, i.e., in the form of iron powder and anhydrous FeCl3 powder. The iron addition was also made through the uptake of iron from the crucible walls at high temperature. It was found that when introduced in the form of anhydrous FeCl3, the addition of iron produces significant grain refinement of high-purity Mg-3%Al and Mg-9%Al alloys. The grain refinement was also readily achieved through the uptake of iron from steel crucible surfaces; however, the addition of Fe powder in the form of an ALTAB™ Fe75 powder compact (75%Fe, 15%Al and 10% Na-free flux) did not cause grain refinement. The result obtained from the grain refining tests conducted in ceramic crucibles and an ultra-low carbon 316L stainless crucible indicated that the grain refinement of Mg-Al alloys by Fe inoculation has little to do with the Al4C3 hypothesis. It was considered that the particles containing Mg, Al, Fe and O are probably the nucleants for the magnesium grains. © Institute of Materials Engineering Australasia Ltd.