Intermetallic Compound Formation in Al/Mg Friction Stir Welded (FSW) Butt Joints

In this work, friction stir welding (FSW) is used to produce butt joints of 3-mm-thick sheets of AZ31B magnesium alloy to two different aluminum alloys: AA1100 (minimum 99% aluminum) and AA6061 (97.9% Al). The paper reports on utilizing metallurgical techniques to determine the distribution profiles of elemental aluminum and magnesium within the joints were produced using energy dispersive x-ray spectroscopy (EDX). Furthermore, X-ray diffraction (XRD) was used to identify the intermetallic compounds that form in the joints as a result of the stirring action at processing temperatures. Measurements confirmed the presence of primary intermetallic compounds in the welded joints and were identified to be the α-phase (Al12Mg17) and the β-phase (Al3Mg2). Lastly, micro-hardness studies were conducted at the intermetallic-compounds-rich locations resulting in hardness profiles.