Microstructural and mechanical property of friction stir welded Al7075/TiB2 aluminium matrix composite

Abstract The present investigation reports the effect of Titanium diboride (TiB2) reinforcement on microstructure and mechanical properties of friction stir welded 6 mm thick AA7075/TiB2 as-cast aluminum matrix composite (AMC) joints. The study has been designed by varying the weight % (wt%) of reinforcement (6%, 9% and 12%) in the base material plate and welding at a constant tool traverse speed, tool rotational speed and tilt angle. For phase analysis of base material, XRD analysis was performed to determine the presence of TiB2 in the composite material. Macro and microstructural analysis of welded samples were performed using low and higher resolution light optical microscopy. From the macrostructural analysis it is confirmed that, all the welded samples are sound and defect free. From microstructural analysis it was observed that fine equiaxed grains were present in the nugget zone (NZ) and elongated grains were present in the thermo mechanically affected zone (TMAZ). Maximum ultimate tensile strength (UTS) and yield stress was obtained at 12 wt% reinforcement and minimum UTS and yield stress was obtained at 6 wt% reinforcement. Hardness of the welded joint increases with increase in the wt% of the reinforcement in base material. Fractography analysis showed the occurrence of ductile mode of fracture of the welded joints.