Effect of friction stir processing parameters on producing AA6061/ tungsten carbide nanocomposite

Abstract

Friction stir processing (FSP) is a modern manufacturing strategy for improving the surface characteristics of materials by modifying their surface via localized plastic deformation. This research focuses on optimization process parameters for tungsten carbide-reinforced 6061 aluminum alloy surface composite using FSP. The effect of the process parameters including tool rotational speed, transverse feed, number of passes, and tungsten carbide particles volume fractions, on ultimate tensile strength (UTS) and grain size of fabricated AA6061/WC surface nanocomposites are investigated. For four factors and three levels, the L27 Taguchi technique is used to formulate the experimental design. The analysis of variance (ANOVA) is used to determine the significance and the percentage contribution of each parameter. The desirability approach is used to optimize the process parameters in terms of tensile strength and average grain size. The results indicate that the proper selection of FSP parameters results in a homogeneous distribution of the WC particles throughout the matrix thereby producing a defect-free AA6061/WC nanocomposite without voids. Also, the severe plastic deformation and heat generation during FSP causes the breaking of coarse particles, WC particles, elimination of porous holes and creates an ultrafine grain-sized structure via dynamic recrystallization. Furthermore, it was concluded that the transverse feed is the most significant factor for ultimate tensile strength with 40.1% contribution whereas the number of passes is the most significant factor for grain size with a 34.7% contribution. The optimum combination of the current process parameters is found to be 1800 rpm rotation speed, 120 mm/min transverse feed, 4.3636% volume fraction, and 3- pass for optimum values of UTS and grain size. The surface composite developed in this work is considered appropriate material for applications requiring lightweight and improved surface properties, such as aerospace, automotive, marine, defense and transportation industries.