Effect of Cooling Rate on Structure and Properties of Aluminium-Silicon Alloys

摘要

Aluminium-silicon alloys have the potential for excellent castability, good weldability, good thermal conductivity, high strength at elevated temperature and excellent corrosion resistance as well as wear resistance properties. They are therefore, well suited for aerospace structural applications, automobile industry, military applications, etc. However, the structure and properties of aluminium-silicon alloys are very much dependent upon the composition, cooling rate, modification and heat treatment. In this study, the effects of cooling rate have been tried and in order to do so, round cast to shape and size test bars were produced in the green sand moulds and the metallic chill moulds. The green sand mould produces slowly cooled casting, while the metallic chill mould produces rapidly cooled casting. The rate of cooling during solidification/freezing affects the structure and properties of the aluminium-silicon alloys. Due to rapid solidification, the sharpness of the primary silicon crystals and the eutectic silicon needles were reduced. As a result, rapid cooling produced castings having greater strength and ductility than the slowly cooled castings. At the same time, increase of silicon contents in the Al-Si alloy beyond eutectic level, decreases the tensile properties for both rates of cooling.