Determination of the main parameters of resistance spot welding of Al-5 Mg aluminum alloy

Introduction. The resistance spot welding (RSW) process has proven to be widely applicable across various industrial sectors, especially for mass production. Typical fields of application include aerospace, automotive, furniture manufacturing, and other industries. However, the RSW process presents certain challenges when welding aluminum and its alloys. Generally, aluminum alloys produce poor welds due to their physical and metallurgical properties such as oxide formation, thermal expansion and contraction, lower weldability, and the formation of intermetallic compounds. This study aims to evaluate the feasibility and mechanical characteristics of RSW joints in Al-5 Mg aluminum alloys. The purpose is to assess the potential of resistance spot welding for aluminum alloys and to determine the influence of key RSW parameters on the microstructure and properties of the weld. Research methods. Al-5 Mg aluminum alloy sheets in as-received condition were used. Spot welding was performed using a stationary resistance spot welding machine MT-4240. Samples for analysis were cut, polished, and subsequently examined under an optical microscope. Hardness measurements were carried out using a microhardness tester along two directions: radially across the nugget and through the sheet thickness, employing a 100 g load. An Instron electromechanical testing machine was utilized for shear testing at a constant traverse speed of 1 mm/min until complete joint failure at room temperature. The nugget diameter was measured on the fracture surface after shear tensile testing. Results and Discussion. Optimal input parameters for welding 2.5 mm thick aluminum sheets were identified, and three output variables were analyzed: tensile strength, joint hardness, and nugget diameter. It was observed that joint strength improved significantly with increased process parameters (welding current and welding period). Nugget diameter showed a clear correlation with input parameters related to current and welding period. An increase in process parameters, i.e., weld cycle time, electrode force, and welding current, led to an increase in nugget size. The ratio of weld strength to base metal strength reached approximately 0.9. It is demonstrated that resistance spot welding of 2.5 mm thick Al-5 Mg aluminum sheets is feasible and can be employed in various industrial applications.