Effect of Heat Treatment on Controlling the Morphology of AlFeSi Phase in A380 Alloy

Abstract

In most aluminum–silicon-based die casting alloys, iron is considered one of the most harmful elements. The presence of iron in Al–Si-based alloys leads to the precipitation of a series of iron-containing intermetallic phases. Of these, the β-AlFeSi phase is the most detrimental to the toughness of Al–Si-based alloys. Reducing the formation of the β-AlFeSi phase has the potential of significantly improving the ductility of die casting alloys. The purpose of this work is to show how combined use of high-temperature and short-time heat treatment can be an effective way of controlling the morphology and fraction of β-AlFeSi phase in A380 alloy. Experimental results indicate that if heat treatment temperature goes up to 500 °C (932 °F), the higher temperature can reduce formation of β-AlFeSi with shorter heat treatment time. Evidence of this reduction is proved in optical and scanning electron microscopy images showing both the decomposition of β-AlFeSi and the transformation of β to α-AlFeSi.