Determination of Optimum Percentage Addition of Magnesium in 319 Aluminum Alloy

Abstract

The use of aluminum and magnesium alloys in the automobile industry is continuously increasing. The driving force is reduced green house gas emissions resulting from light weighting of the vehicles and efficient scrap recycling. The aluminium alloy castings are generally used in automotive, aerospace, defense and general engineering industries. Among the commercial aluminium castings, Al 6Si – 3Cu (319) is widely used mainly because of its excellent cast ability, high strength to weight ratio, good mechanical properties, lower coefficient of thermal expansion, low recycling cost and corrosion resistance. The present study was performed on 319 Al alloy to investigate the effect of magnesium addition as well as other melt treatment parameters such as Sr modification and grain refinement on the heat treatment behavior of the alloy. T6 treatment was carried out on the alloy taking an optimum temperature of 500°C-10 hours, for solution treatment followed by 60°C water quenching and 170°C8 hours for artificial ageing. The results show that increasing the Mg content in Al 319 up to 0.45% considerably enhances the alloy response to heat treatment in the T6 temperatures. Addition of Mg in amounts of the order of 0.45% results in the precipitation of Al5Mg8Si6Cu2 phase particles. Modification with Sr tends to cause severe segregation of Cu-containing intermetallics in areas away from the growing Si regions. Various tests like tensile, fatigue, wear and hardness are done on the various castings and the results are compared.