Tensile performance modeling and process optimization of AA6061-T6/WC surface nanocomposites developed via friction stir processing

In the present investigation, friction stir processing (FSP) is implemented to develop the tungsten carbide (WC) nanoparticle-reinforced aluminum alloy Al6061-T6. The tensile properties of the Al6061-T6/WC surface nanocomposite were evaluated in relation to the volume fraction of WC nanoparticles, the number of passes, rotation speed, and traverse speed. The experiments were designed using the Box-Behnken Design (BBD) of response surface methodology (RSM). For identifying the significant variables and interaction implications, analysis of variance (ANOVA) was performed. The models generated demonstrate that rotating speed is the most significant variable and transverse speed is of little importance. Heat input to FSP increases as traverse speed decreases and tool rotational speed increases. Increasing the number of FSP passes effectively broke the coarse and dendritic clusters, refined the matrix grains, and dynamic recrystallization (DRX) resulting in equiaxed grains that, through restricted dislocation activity, exhibit tensile behavior. Furthermore, the extreme plastic deformation and heat production during FSP results in the breakage of WC particles and coarse particles, the removal of porous holes, and DRX of an ultrafine grain-sized structure. The optimized surface nanocomposite with the highest tensile strength (315 MPa), yield strength (221 MPa), and elongation (9.7%) was achieved at volume fraction 2%, number of passes 5, rotation speed 1000 rpm, and traverse speed 30 mm/min. The surface composite that developed has been identified as an appropriate material for the automotive, aerospace, marine, defense, and transportation sectors, among others, that require lightweight and improved surface qualities.