Effect of ALCLAD layer on weld characteristics during dissimilar micro-friction stir welding (μFSW) of aluminum alloy sheets

Abstract

Welding of ALCLAD materials in similar and dissimilar configurations is a necessary requirement in engineering applications, and the presence of the ALCLAD layer might cause major issues during the welding process. So, in the present work, dissimilar micro-friction stir welding of 0.5 mm thick AA6061-T6 with ALCLAD 2024-T3 and AA6061-T6 and bare 2024-T3 was carried out at constant process parameters of 2000 rpm and 175 mm/min. Microstructural analysis and mechanical testing (hardness and tensile test) of the welds were carried out to investigate the influence of the ALCLAD layer on the weld characteristics. Moreover, the two welds were compared with each other for a better understanding of the same. The interaction condition is altered by the presence of a soft ALCLAD layer at the tool-workpiece interface, resulting in less material deformation and intermixing in the weld zone. Furthermore, the inflow of the ALCLAD layer was observed from the bottom side of the weld, which acts as a point of stress concentration and affects the weld performance. Superior tensile properties with the highest weld efficiency of 76.1% were obtained for the weld produced with bare 2024 because of a higher degree of material intermixing and the absence of any defects. Moreover, in this case, the weld fractures from the heat-affected zone of the 6061 side. Furthermore, similar fracture morphology was obtained throughout the thickness for the weld produced with bare 2024, but the weld produced with ALCLAD 2024 has different morphology across the thickness.