Optimization of Parameters for Maximum Tensile Strength of Friction Stir Welded AA6082/Si3N4 and AA6082/SiC Composite Joints

Weldability, microstructure evolution and tensile strength of an aluminium alloy (AA6082) and of two category of composites with AA6082 matrix reinforced with Si3N4 and SiC particles during friction stir welding (FSW) were investigated. 5, 10 and 15 weight percentage of reinforced particle were used in each category. FSW was carried out as per the parameters selected by Taguchi L-9 orthogonal Array. Microstructure of nugget region was investigated by scanning electron microscopy (SEM) and EDS analysis. Effect of tool rotational speed, welding speed and tool tilt angle on tensile strength was also investigated. The optimum parameters to get maximum ultimate tensile strength (UTS) for AA6082/SiC and AA6082/ Si3N4 composites were found out. On one hand, SiC particles are fractured thus fined due to intensive stirring action during FSW. On the other hand, the plastic flowing of material in the weld is benefit to eliminate microporocities existed in original base material. The highest tensile strength of 193 MPa was obtained for AA6082/15 wt% Si3N4 composite, at tool rotation speed of 1950 rpm at fixed welding speed of 40 mm/min and fixed tool tilt angle of 2°. Hard Si3N4 particles transfer their strength to the AA6082 matrix by their strengthening mechanism. This happens because of load transfer from Si3N4 particles to AA6082 matrix.