Influence of modification and heat treatment on proprties of a1alloy a357

Abstract

The research for new materials that could be used for components with complex geometry in automotive and aircraft industries led to exploitation of Al-Si-Mg alloys. The Al-Si-Mg based cast alloys possess very good mechanical properties and ease in formability has attracted attention as potential materials. newlineA survey of pertinent literature was carried out on materials, casting methods, modification, heat treatment, processing of Al-Si alloys. The research was especially directed on the effect of these parameters on microstructure (Silicon morphology and dendritic cell size), mechanical properties, wear characteristics and corrosion characteristics. newlineBased on literature survey Al-Si-Mg (A357) alloy was selected for the present study with the following objectives newline1. Production of Al-Si-Mg (A357) alloy castings by sand casting method and permanent mould casting method in newlinea) As Cast condition, newlineb) Modified condition with suitable amounts of sodium, newlinec) Modified condition with suitable amounts of strontium, newline2. Heat treatment of above castings by solutionization and age hardening for different time periods. newline3. Microstructure analysis using metallurgical microscope with image analyzer. newline4. Evaluation of mechanical properties such as hardness, wear characteristics, machinability and corrosion characteristics. newline5. Discussion of results and conclusion. newlinev newlineIn this present investigation, Al-7.0Si-0.6Mg (A357.0) alloy castings were produced by sand casting method and by permanent mould casting method. Melt practice was carried out using coke fired furnace and electric arc furnace. For substantial improvement in mechanical properties modification was carried out adding 0.01% Sodium and 0.01% strontium to the molten metal just before pouring into moulds. newlineStrength can be enhanced further by precipitation of Mg2Si in the supersaturated Al solid solution by solutionization treatment and age hardening to T6 condition. solutionization temperature was selected from Al-Mg2Si pseudo phase diagram. Sand cast and permanent mould cast A 357 spec