The Effect of Heat Treatments on the Microstructural Evolution of Twin-Roll-Cast Al-Fe-Si Alloys

Abstract

Dilute Al-Fe-Si alloys with different Fe-Si ratios were prepared by twin-roll casting, rolling and heat treatment. Tensile measurements, optical microscopic observations and electron microscopy observations were performed to investigate the effects of heat treatments on the properties and microstructure evolution of the Al-Fe-Si alloys. The results indicate that in twin-roll cast dilute Al-Fe-Si alloys, the β-AlFeSi, αc-Al12Fe3Si and α'-Al8Fe2Si phases coexist. Eutectic αc-Al12Fe3Si can be observed due to the higher Fe concentration in the center layer. In a twin-roll cast Al-0.36Fe-0.4Si alloy, annealing at temperatures of 400 °C or higher would lead to the refinement of intermetallic particles, which is due to the partial dissolution of intermetallic particles or the decomposition of Si-rich phases. During a slow cooling period after annealing, the coarsening of the α'-Al8Fe2Si phase occurred below 400 °C after partial dissolution. The recrystallized grain size is not obviously affected by the evolution of intermetallic phases. The morphologies and types of intermetallic phases in twin-roll cast Al-0.44Fe-0.24Si alloy are unaffected by the heat treatments.