Mechanical and metallurgical properties of friction stir welded dissimilar joints of AZ91 magnesium alloy and AA 6082-T6 aluminium alloy

In the present research work, AZ91 magnesium alloy and AA6082-T6 aluminium alloy were joined by friction stir welding process. The comparison of microstructure and mechanical properties between different joints by varying the different materials on advance and retreating sides were mainly studied. Four different welds have been prepared to find the material mixing between the similar and dissimilar joints. The joint interfaces of the welds have been investigated by employing an optical microscope and scanning electron microscope. When Mg was placed on advancing side (AS), more aluminium content was soluble in nugget zone than the case where Mg was placed on the retreating side (RS). Thin intermetallic layer in the joint interface of Mg/Al and thick intermetallic layer with poor adhesion of the aluminium and magnesium have been observed in the dissimilar joints varying the sides. The highest UTS of 172.3 MPa was found for Mg-Al when Mg was placed on AS and lower UTS of 156.25 MPa was obtained when Mg was placed on RS. Hardness of 86 Hv and 89 Hv were observed in the Stir zone for the dissimilar AZ91 Mg alloy and AA6082-T6 Al alloy when AZ91Mg alloy was placed on the AS and on the RS respectively. Fractography was also carried out to find the mode of failure.