Fabrication and multi-objective optimization of friction stir processed aluminium based surface composites using Taguchi approach

Friction stir processing is a technique for the modification and fabrication of surface composites. Surface composites of aluminium have a diverse application in industries like aerospace and automobile. Here, B4C nano-particles (< 30 nm) have been employed as the reinforcement on AA7075 based substrate alloy and surface composites have been constructed at varying Tool rotation and Tool traverse speeds. The influence of these varying factors on the ultimate tensile strength (UTS), microhardness (Hv) and residual stress (RS) have been studied. Taguchi L9 orthogonal array was used for the DOE and the changes in the mechanical properties of these nine samples with regards to the tool rotation speeds of 800 rpm, 1000 rpm and 1200 rpm and the tool traverse speeds of 40 mm min(-1), 50 mm min(-1) and 60 mm min(-1) were investigated. It was found that between the two processing variables, Tool traverse speed was the more significant variable. 800 rpm and 60 mm min(-1) were determined to be the optimum parameters for Friction stir processing and the predicted values of microhardness (Hv) through Taguchi analysis were the most accurate.