Characterization of AA7075 Weldment using CMT Process

Abstract

The use of aluminum alloys due to high strength to weight ratio and better mechanical properties endorse their application in aerospace and automotive industries. The need to develop better welding technique came out for frequent joining of the similar and dissimilar metals together without increasing the heat affected region and lowering heat input. This study was aimed to investigate the weldment characteristics of 6 mm thick AA7075 double butt joint by cold metal transfer (CMT) process which uses low heat input compared to other welding techniques with ER5356 as a filler wire. Bead on trials revealed the depth of penetration of the weld and thus parameters for double sided butt joint were decided. The welded joint was characterized by means of optical microscopy and energy dispersive spectroscopy. Mechanical properties were measured by tensile test and impact test. Under the optimized welding parameters, the ultimate tensile strength of the joint was found to be 181 MPa, reaching 40% of the aluminum alloy base metal, whereas the impact energy was found to be 5.95 N-m which was 52.4 % less than the base alloy. The low efficiency of the weld can be seen due to weld defects which can be further reduced by reversing the direction of bottom side of plate while welding and increasing inert gas pressure.