Mechanical, microstructural and fracture properties of dissimilar welds produced by friction stir welding of AZ31B and Al6061

Friction stir welding (FSW) has been used for joining AZ31B magnesium alloy and Al 6061-T6 aluminum alloy sheets. In this regard, the current work aims to study the mechanical, microstructural and fracture properties of dissimilar FSW welds obtained by evolving the tool rotation and translation speeds. The dissimilar welds microstructure and mechanical properties are evaluated and correlated with the FSW parameters to obtain the optimum weld conditions. The results showed that placing aluminum on the advancing side of the weld resulted in better quality welds. The evaluation of the microhardness along the joint section showed values evolving between the microhardness values of the base metals (Al and Mg). A discontinuity in the microhardness values, attributed to the intermetallic compounds (IMC) present, was observed at the weld interface between Mg and Al sheets. The room temperature tensile testing of the weld showed weld joint efficiency between 18% and 55% and at higher temperatures (200°C) joint efficiency was observed to be between 58% and 78%. The specimen showed brittle behavior under tensile testing, and the specimen fracture occurred along the weld joint. The specimen fracture seems to have initiated in the brittle Mg2Al3 and Mg17Al12 IMCs formed between the welded sheets.