Effect of Input Heat on Microstructure and Mechanical Properties of Aluminum 5456 Thin Sheets Welding by TIG and MIG Methods

In this study, the effect of the heat input on the microstructure and mechanical behavior of the 5456 series aluminum thin sheets in two processes of gas tungsten arc welding (GTAW) and gas metal arc welding of (GMAW) was investigated. For this purpose, the aluminum base metal with a thickness of 0.9 mm, ER5356 as metal filler with a diameter of 1.2 mm and argon gas were used. Microstructure and fracture surface were studied by optical microscopy and scanning electron microscopy respectively. Also, to study the mechanical properties of the joint, the tensile and microhardness tests were used. The results shows that the microstructure of TIG and MIG welding process is coaxially dendrite and dendritic columnar respectively. The microstructure of TIG welded sample was finer than MIG welded sample as a result of lower heat input and lower temperature gradient. This event cause increase in strength and elongation in TIG welded sample compared to MIG welded sample. Also, the fracture surface of TIG sample is consists of the fine dumplings and funnel-shaped cavities, and so the ductile fracture has occurred, but the semi brittle failure was done in the MIG sample.