Structural and mechanical modifications of hyper-eutectic Al–16Si alloy using friction stir processing

Abstract

Abstract This study explores the structural and mechanical enhancements of hypereutectic Al–Si (16% Si) as-cast alloy achieved via friction stir processing (FSP), with travel speed as the variable parameter (26, 33, 42, and 52 mm/min) at a constant tool rotational speed of 1330 rpm. The findings reveal substantial improvements in the alloy's microstructure and mechanical characteristics. At travel speeds of 26, 33, 42, and 52 mm/min, primary silicon (Si) particle sizes were reduced by 65.9%, 74.47%, 34.76%, and 81%, respectively, compared to the as-cast condition. Correspondingly, the aspect ratio of Si particles decreased by 50.43%, 59.89%, 56.19%, and 54.03%, respectively. The highest tensile strength (155.53 MPa) and microhardness (78.24 HV) were achieved at a travel speed of 52 mm/min. Under dry sliding conditions, wear rates decreased by 66.7%, 36.3%, 22.1%, and 55.6% for the FSPed samples at travel speeds of 26, 33, 42, and 52 mm/min, respectively, compared to the as-cast sample. Similarly, the coefficient of friction under these conditions was reduced by 31.81%, 27.27%, 18.18%, and 29%, respectively. The most significant enhancements were observed at a travel speed of 52 mm/min, including an 81% reduction in primary Si particle size, a 54.03% decrease in aspect ratio, a 34.3% increase in microhardness, and a 29% reduction in the coefficient of friction under dry sliding conditions. These findings highlight the potential of FSP to substantially improve the structural and mechanical performance of hypereutectic Al–Si alloys, emphasizing the importance of optimizing travel speeds for maximum effectiveness.