Assessment of self-reacting bobbin tool friction stir welding for joining AZ31 magnesium alloy at inert gas environment

Research work presented in this study has the primary target of exploring joint attributes of AZ31 magnesium alloys using friction stir welding process with a modified tool referred as bobbin tool. Effects of inert and open atmosphere on mechanical properties are evaluated over a wide range of welding speed and tool rotation speed. Comparison of the research findings from the inert atmosphere bobbin tool were made with the traditional process of friction stir welding. The results depicted improved joint properties for inert atmosphere welding. Low and intermediate range of tool rotational speed is found to be favorable for bobbin tool friction stir welding without and with an inert medium, respectively. Controlled atmosphere due to inert medium leads to less oxidation of the AZ31 Mg alloy leading to superior joint properties. Microstructural investigations are also made with the aim of evaluating the impact of bobbin tool and inert medium on joint properties. In each aspect for joining of AZ31 Mg alloy, bobbin tool with inert medium is found to be an effective solution for joining with improved mechanical properties compared to without inert bobbin tool as well as conventional tool friction stir welding. (C) 2019 Published by Elsevier B.V. on behalf of Chongqing University.