Fabrication and post processing techniques to enhance the strength of Al-Si alloy

Abstract

The alloy of aluminium and silicon was fabricated at the shop floor level and post processed with the sole intention of enhancing the tensile and compression strengths of the alloy for engine piston application. To that extent, alloys of aluminium with varying fractions of silicon in the range of 12%, 18% and 24% by weight was fabricated using the die casting technique. The alloys casted in the form of cylindrical rods were post processed using heat treatment techniques. This post processing techniques includes the heat treatments at 500 °C for one set of casted Al-Si alloys and 520 °C for the other set of casted Al-Si alloys, each for a period of 3 h and then water quenched. Following which, both the sets of alloys were age hardened, by heat treating at 155 °C for a period 2 h and then air cooled. The tensile and compression tests were conducted to evaluate the ultimate tensile and compression stresses of the heat treated specimens and the results obtained were compared with the stresses obtained for the as cast Al-Si alloys. It was observed that the Al-Si alloy fabricated with 18% silicon, heat treated at 500 °C for a period of 3 h and age hardened at 155 °C had shown an excellent tensile strength improvement at 89.91 MPa. In addition, Al-Si alloy fabricated with 18% silicon, but heat treated at 520 °C for a period of 3 h and age hardened at 155 °C had shown an excellent compression strength improvement at 381.97 MPa. Thus, it can be comprehended that the fabrication of Al-Si alloy with 18% silicon and the post processing techniques adopted through heat treatments showed a vast improvement in tensile and compression strengths, which can be applicable for engine pistons.