Effect of Semi-Solid Heat Treatment on the Microstructure and Dry Sliding Wear Behavior of Al–20Si Alloy at Optimized Parametric Conditions

Hypereutectic Al–20Si alloy needs optimization of different process parameters in order to obtain maximum wear resistance for tribological applications aerospace and automobile industries. The present study attempts to find the best possible combination of the process parameters for the semi-solid heat treatment of the alloy in Taguchi Method. The effects of three different control variables i.e. sliding velocity, sliding distance, and load on the wear characteristics were investigated. The optimal values of control factors were determined on the basis of ‘smaller-is-better’ approach from Taguchi optimization technique. The optimized conditions for wear tests were then applied to the isothermally heat-treated samples (10–30 min) at 600 °C. The quantitative analysis shows the significant change in the size, morphology, and distribution of primary Si and eutectic Si with heat treatment. Moreover, the worn surfaces were analyzed from the microstructures obtained in Field Emission Scanning Electron Microscopy (FESEM). The improved wear resistance observed in the case of 20 min of holding time can be attributed to the combined effect of refinement of primary Si, modification of eutectic Si and equiaxed α-Al during semi-solid heat treatment.