Development of Pulsed Cold Metal Transfer and Gas Metal Arc Welding Techniques on High-Strength Aerospace-Grade AA7475-T
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Development of Pulsed Cold Metal Transfer and Gas Metal Arc Welding Techniques on High-Strength Aerospace-Grade AA7475-T761 T.A. Vigneshwara Kumaran, S.A. Nithin Joseph Reddy, S. Jerome, N. Anbarasan, N. Arivazhagan, M. Manikandan, and M. Sathishkumar Submitted: 24 July 2020 / Revised: 12 September 2020 / Accepted: 25 September 2020 High-strength aluminum alloy (AA7475) sheets are widely used in aerospace sectors due to its better performance, global suitability, and multifunctional features. The welding of AA7475 in the fusion welding process like gas metal arc welding (GMAW) is difficult due to cracks generation. However, these problems could be overcome by different variants of GMAW process, like pulsed and normal cold metal transfer (PCMT and NCMT) techniques. The main objective of this research work is to deliver a better insight into mechanical and metallurgical properties of butt joint welded AA7475 through PCMT, NCMT, and GMAW techniques with ER5356 and ER4043. The defects-free butt joints were observed for PCMT, NCMT, and GMAW processes with ER5356, whereas the presence of porosities is found for ER4043. The microsegregation of Fe, Si, Mg, Zn, and Cu leads to the emergence of Mg2Cu, Mg2Si, Al2Cu, Al2CuMg, MgZn2, Mg2Zn11, and Fe2Al6 phases in the AA7475 weldments. The development of binary brittle intermetallic Mg2Si phase affects the tensile strength of all weldments made with ER4043. Better joint efficiency (96.11%), impact toughness (12.1 ± 0.8 J), and microhardness (119 ± 7.4 HV) are found in PCMT with ER5356 compared to other processes. Because of the low heat input utilised, PCMT provides better joint strength and microstructural integrity than NCMT and GMAW. Keywords
AA7475, intermetallic phases, impact toughness, joint efficiency, pulsed cold metal transfer (PCMT)
1. Introduction In recent days, transportation industries consume around 20% of the worldÕs energy utilisation. The role of lightweight materials saves energy, and it also improves efficiency. Especially, the use of aluminum alloys places a significant role in the parts of transportation industries such as aerospace industries, marine field, and automobile industries. After iron and steel material, the aluminum alloy is mostly used in the transportation sectors. These alloys have high formability, good weldability, moderate mechanical properties, and excellent corrosion resistance as significant advantages compared to steel (Ref 1-4). Among the different types of aluminum alloys, highstrength 7XXX series (treatable by heat) alloys like AA7475 are widely used in the fabrication of the aircraft parts. AA7475 has a combination of better fracture strength and improved strength compared to the available high-strength aluminum alloys under aerospace grade. A combination of required T.A. Vigneshwara Kumaran, N. Arivazhagan, M. Manikandan, and M. Sathishkumar, School of Mechanical Engineering, Vellore Institute of Technology, Vellore 632014, India; S.A. Nithin Joseph Reddy, School of Mechanical Engineering, Vellore
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