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Mg-NiTi-based metal matrix composites are appropriate solutions for the two most important goals of material engineers in the present day, i.e., imparting functional behaviour and the light weighting of metallic structures. In recent years, due to its solid-state nature, the development of Mg-based metal matrix composites has largely benefited from friction stir processing. Despite the great effort of researchers in the domain of friction stir welding and processing, finding optimum process parameters for efficient material mixing and consolidation remains a rigorous and exhaustive challenge. Tool offset variation has been seen to aid the integrity and strength of friction stir welds; however, its effect upon the stir zone structure, material flow, particle distribution, and defect formation has not been investigated for friction stir processing. Therefore, the authors employed Mg as the base metal and NiTi shape memory alloy as the reinforcement to the targeted metal matrix composite. The tool offset was linearly varied by tilting the slotted length with respect to the traverse direction. Friction stir processing performed at a rotational speed of 560 rpm and traverse speed of 80 mm/min revealed crucial changes in defect morphology and area, which has been explicated with the quantified variation in tool offset from the advancing side to the retreating side. For the positive offset conditions, i.e., tool offset towards the advancing side, the shape of the tunnelling defect was chiefly convex from the outward direction. Meanwhile, for the negative offset conditions, i.e., tool offset towards the retreating side, the tunnelling defect exhibited a concave outward shape. A transition from rectangular to triangular morphology was also observed as the tool moved from an offset of 1.75 mm in the advancing side to 1.75 mm in the retreating side.

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Dissimilar Friction Stir Welded T-joints gives auxiliary strength to engineering structures, keeping insignificantbody weight. Due to the stronger material being away from the heat source, the T-joint between AA8011 and AA5754 is very vulnerable to formation of defects which results in lower tensile strength along the skin and stringer. In this paper, two aluminium alloys, namely AA5754 and AA8011 were friction stir welded in the Tjoint configuration, and the roles of welding parameters such as the tool transverse speed, tool rotational speed, and tool shoulder diameter on the tensile strength along skin and stringer was analyzed and discussed. The relative importance of the three process parameters was also analyzed. The tool shoulder diameter is found to be the most dominant factor for the strength along the skin, whereas, tool transverse speed is found to be the most important for the strength along stringer.

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