Grain refiner for Al-Si alloys

Abstract

Over the last few decades the grain refinement practice using Ti based chemical additions (Al-Ti-B) is well established for wrought Al alloys, however in the case of Al-Si casting alloys, the practice of adding grain refiners and the impact on castability is not well established in industries, due primarily to chemical instability of conventionally known Ti based grain refiner with Si element in the melt. Research at Brunei University has identified a novel chemical composition that can effectively refine grain structure of Al-Si castings alloys. First, the effect of addition of grain refiner, in the form of powder addition, on micro structural and mechanical properties of LM6 (A423) and LM25 (A356) alloys was investigated. Afterwards, a suitable method to produce the novel grain refiner in the form of master alloy was developed and the effect of addition of master alloy on grain refinement of the previously mentioned Al-Si alloys was studied.