Microstructure and mechanical properties of Al-Si alloys processed by strain induced melt activation

Abstract

Semi-solid metal processing (SSMP) is an effective near net shape forming processes that have many advantages over the conventional metal casting process. The strain induced melt activation (SIMA), one of the SSM processes, is adapted to produce Al-Si alloys with near globular microstructure. Among the cast alloys, Al-Si alloys are widely used in automotive applications owing to their high wear resistance, moderate strength to weight ratio and low thermal expansion coefficient. Conventionally cast Al-Si alloys have dendritic structure and contain defects such as porosity, blow holes, shrinkage etc. To overcome this defect, semi-solid metal processing is used to obtain globular structure with enhanced mechanical properties.In this investigation, the effects of silicon percentage on mechanical properties and microstructure of Al-Si alloys produced through SIMA process was investigated. Al-Si alloys containing 7%, 12% and 14% wt% Si were prepared through melting and casting route. The microstructure and mechanical properties of conventionally cast and modified SIMA processed Al-Si alloys were observed and evaluated. The SIMA processed samples show significantly higher properties than the samples prepared through conventional cast route. The UTS increased but percentage of elongation decreased with increasing Si wt %. The better combination of mechanical properties obtained when 60% deformed Al-7wt%Si alloy was isothermally hold at temperature 585°C for 30 min.