Experimental and numerical evaluation of squeeze cast Al-Si-Cu-Ni-Mg alloy for piston applications

Al-12% Si is the commercial alloy commonly used to make pistons by using gravity casting method. When this alloy was modified with Ni, Cu, and Mg (modified alloy), it showed an adequate fluidity during casting and achieved higher strength. However, the addition of alloying elements reduces its thermal characteristics. Therefore, an attempt has been made to improve the thermal conductivity through modifying the microstructure. It was done by changing the cast method to squeeze cast, adding 0.04%Sr (Sr-modified alloy) and post-heat treatment (T6 and T7). Results highlighted that the sample of gravity cast-Sr-modified alloy showed enhancement in thermal conductivity. Even though squeeze cast-Sr-modified alloy showed reduction in thermal conductivity of few percentage, it possessed better strength, however the heat treatment (T7 condition) showed a noticeable increment in thermal conductivity. Therefore, it is concluded that T7-heat-treated squeeze cast-Sr-modified alloy showed an excellent combination of strength and thermal conductivity making it an ideal material for piston applications. The piston component was studied by numerical steady state thermal analysis using ANSYS Workbench, obtained a maximum heat flux of 1.80 W/mm(2) for Al-Si piston alloy aged for 11 h (T7), which is in agreement with the experimental results.