Comparative Studies on Normal and Pulsed Cold Metal Transfer Welding of Aerospace Grade Aluminum Alloy 2024

Abstract

Abstract Aluminum alloy 2024 (AA2024) sheets are mostly used in the fuselage and wings of the aircraft and structural applications; it is because of better fatigue resistance and high strength. The joining of AA2024 through gas metal arc welding (high heat input) is complicated because of hot cracking (solidification cracking), softening of the heat-affected zone (HAZ), and formation of porosity. However, these problems could be minimized by employing cold metal transfer (CMT) (low heat input) welding. The ultimate aim of the present research is to compare the metallurgical integrity and mechanical properties of the butt-welded AA2024 through normal CMT (N-CMT) and pulsed mode CMT (P-CMT) methods. The fine-grain structure observed in the P-CMT contributed better mechanical properties compared to N-CMT. The segregations of magnesium, silicon, and copper have revealed the intermetallic compounds such as aluminum-copper (2:1), Al2CuMg, magnesium silicide, and tetracopper silicide. This results in an intergranular fracture of both N-CMT and P-CMT joints. Besides, P-CMT exhibited a higher ultimate tensile strength and % elongation than the N-CMT. Also, the joint efficiencies of N-CMT and P-CMT were 64 % and 68 %, respectively. Furthermore, the hardness value in HAZ of N-CMT (93 HV) was inferior to P-CMT (126 HV). Hence, P-CMT is recommended for joining AA2024 compared to N-CMT.