Preparation and investigation of composites on Aluminium surfaces by friction stir processing

Abstract

Aluminium alloys are extensively used in many applications such as aerospace and defence industries due to the high strength to weight ratio and good ductility. Friction stir processing (FSP) is a technique based on the principles of friction stir welding (FSW) used to produce composites. In this work, the formulation of a mathematical model with process parameters of rotational speed, feed rate, number of passes and tool shape are used to predict the response or the mechanical properties of friction stir processed of 1050 aluminium alloy (yield strength, ultimate tensile strength, percentage elongation and microhardness). A central composite design with four factor, each factor with five levels was used and a response surface methodology (RSM) was applied to develop the regression models to predict the responses. Method of analysis of variance ANOVA was applied to figure out the significant process parameters that have effect on the responses. These results point out that the friction stir processing of 1050 aluminium alloy with 1500 rpm rotational speed , 116 mm/min feed rate , 3 FSP passes and square tool shape, have the maximum predicted responses using response surface methodology (RSM). Those optimum process parameters were used to fabricate AL/SiC composites with different volume fractions. The FSPed composites samples were investigated by optical microscopy (OM), scanning electron microscope (SEM) and EDX to analysis the microstructural changes within each sample. Mechanical and tribological properties were also investigated through microhardness and tension test in addition to wear resistance. The results show significant improvement in the FSPed and FSPed composites samples where a modified grain structure is obtained in the stir zone indicating the formation of fine equiaxed grains compared to the