Abstract
Aluminum alloys of grade 6xxx and 5xxx are used where strength and corrosion resistance both are important. This paper reports the GMA welding of dissimilar 6061 T6 and 5083 O aluminum alloys and comparison of mechanical properties and fracture behavior of dissimilar joints (6061 T6-5083 O) with similar joints of the two base materials (6061 T6-6061 T6 and 5083 O-5083 O). GMA welding is used mostly due to high deposition rate, deeper penetration and high welding speed. The fusion welding of dissimilar aluminum alloys faces many problems due to the different chemical compositions and thermal conductivities of aluminum alloys. The dissimilar joint exhibited an average tensile strength of 138 MPa and weld hardness of 74.2 VHN. The scanning electron micrograph of tensile fracture surface was obtained to investigate the mode of failure. The fractograph at top portion of the fractured surface of 6061 T6-6061 T6 joints exhibited smaller grain size and smaller spacing between grains. The fractograph at middle portion showed population of dimples, which is the indication of ductile type of fracture. The fractograph at bottom portion (root region) indicated relatively smaller cleavage facets in similar joint of 5083 O-5083 O.