SEMI-SOLID SOLIDIFICATION STRUCTURE IN GRAIN-REFINED AL-7SI-3CU ALLOY

摘要

The change in the morphology of the dendritic primary α -Al crystals heated at the semi-solid temperatures was examined in Al-7%Si-3%Cu alloy containing 0.1～1.0% Fe. Dendritic α -Al crystals, which were refined by Ti-B addition and solidified with higher cooling rate than 10K/s, spheroidize only by heating up to the semi-solid state without stirring. The size of the spheroidized primary α -Al crystals is about 100 μ m in diameter. The elongation of the as-semi-solid cast materials is superior to that of the conventional gravity diecast materials, causing 9% of elongation even in the alloy containing 1% Fe. The tensile properties of the alloy materials containing small amount of Mn are further improved by changing morphology of Fe intermetallic compounds from needle-like form to Chinese script one.