Welding of thin sheet of Al5456 aluminum alloy by using GTA and GMA welding process

Abstract

Aluminum thin sheets including AA 5456 alloy have been widely used in the marine and aircraft building industries. In the present study, the microstructure and the mechanical behavior of the butt weld joints of the aluminum 0.9 mm thin sheet of Al 5456 Al alloys produced by GTAW and GMAW process were studied using two pulse and alternative currents. The microstructure of the welded joints were studied by optical microscope (OM) and scanning electron microscope (SEM). The mechanical properties were evaluated by microhardness, tensile and bending tests. Also, the fracture surface evaluated by SEM. The results showed that microstructure of the weld metal of all GTAW samples contained a dendritic structure; this was such that the finer grain sizes were obtained in the weld metal of the pulsed samples, whereas by increasing the pulsed time, the grain growth was observed in the GTAW process. In the tension tests, all weldments failed from the HAZ zone, but the two samples welded by GTAW process with 0.2 and 0.3 pulsed time were failed from the base metal. Maximum and minimum tensile strength was obtained in the samples welded by GTAW process with 0.2 pulsed time and the MIG process samples, which was about 5.93% and 32.95 compare to base metal, respectively. The pulsed samples, due to the low heat input, had higher mechanical properties, as compared to the alternate current samples.