Welding of a 7025 Al-alloy by a pulsed MIG welding process

Aluminium alloys are important alloys in industries today, due to their ductile, lightweight and malleable nature. Research into how to effectively weld such alloys is therefore becoming increasingly important because of the considerable advantages of the material. Utilizing the high strength-to-weight ratio of aluminium alloys in welded products remains challenging but attainable. This paper studies pulsed MIG welding of a High Strength Aluminium (HSA) alloy, focusing specifically on the effect of heat input on the welding metallurgy. HSA alloys are used mostly in the aeronautic and automobile industries, e.g., in the construction of train coaches and trailer carriers. Pulsed MIG welding of a 7025-T6 alloy is examined. The methodology for the paper is experimental investigation using a robotized pulsed MIG welding machine. Results are presented based on evaluation of the macrostructure and microstructure using optical microscopy. Mechanical properties (hardness variations) of 7025-T6 alloy welds with a range of heat inputs are also presented. Variations in the welding heat input affect the hardness profile, the weld seam and the weld zone, which is found to be soft compared to the base material. In 7025 aluminium, high heat input allows for higher hardness of the weld interface due to the possibility of solution hardening.