Abstract In this study, AZ31 magnesium alloy sheet was welded by butt joint design by tungsten-gas arc welding process (GTAW) using AZ92 filler metal. The purpose of this study is to optimize welding parameters to increase strength using pulse current and compare it with no pulse mode. The most important parameters of the welding process in this study are Ip (maximum current) and Ib (background current). Welding specimens were welded with different background current (Ib) and constant maximum current (Ip). Weld specimens were also eva‎luated in terms of physical properties (weld width) and mechanical properties (microhardness test and tensile test). An optical microscope was used to study the type of phases, weld metal microstructure, base metal and heat affected area, and a scanning electron microscope was used to examine the refractive levels. The test results are: the weld sample with the lowest field current (20 A) and the heat input (153 J/mm) due to the increase in the cooling rate of the molten pool, causes the production of α-Mg fine phase dendrites in the weld metal. Leads to the highest tensile strength (295 MPa) and microhardness (71 Vickers) among the specimens; This caused a soft fracture of the base metal with a suitable increase in the elongation percentage (7%) in the tensile test. Also, the sample with the highest current ratio (Ib / Ip, with high ground current intensity (80 A) causes high heat input (290 J/mm) in the molten pool, which has the lowest cooling rate of molten pool among the samples, which results in a structure containing coarse dendrites with the lowest average hardness (60 Vickers) was observed, and the sample with no pulse current also has a microstructure containing coarse dendrites due to higher heat input (290 J/mm) and low cooling rate of the molten pool leading to a decrease in the mechanical properties of the weld metal.

اميرحسين ميثمي