Investigation on feasibility of dissimilar welding of AA2124 and AA7075 aluminium alloy using tungsten inert gas welding

• Published in: Materials today : proceedings Vol. 26; pp. 2283 - 2288
• Main Authors: Hima Bindu, A., Chaitanya, B.S.K., Ajay, K., Sudhakar, I.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2020
• Subjects: Coarse grain; Crack; Hardness; Mode of failure; Residual stress; Tungsten inert gas welding; Mode of failure; Hardness; Tungsten inert gas welding; Residual stress; Coarse grain; Crack
• ISSN: 2214-7853; 2214-7853
• DOI: 10.1016/j.matpr.2020.02.494

Now a day’s fuel economy, easy mobility and stringent rules imposed by pollution norms are striving to develop a scope to substitute steel by lighter materials in the transportation industry. Nickel and titanium based nonferrous alloys are usually suitable for high temperature applications and non-availability of magnesium brings an opportunity to replace high density steel with aluminium alloy. Among aluminium alloys, AA2124 and AA7075 aluminium alloy which are heat treatable in nature are widely used in aircraft industries. Ample numbers of investigations are based on the fabrication of these above said materials using friction stir welding, but scanty of literatures are available in the area of fusion welding (especially using tungsten inert gas welding). Thus present investigation aims at joining of above mentioned aluminium alloys using TIG. Various dissimilar weldments are obtained using 100 amp, 110 amp, 120 amp and 130 amp current and filler alloy AA 5356. From the macro inspections of weldments, it is inferred that dissimilar weldment fabricated at 100 amps has shown fewer cracks along the weld zone compared to other weldments. So, it is thought to study the behaviour of weldment under the light of optical microscopy and mechanical testing. SEM analysis on opened crack samples shows that weldments have exhibited inter-granular fracture rather than intragranular one. Similarly, it has been noticed that there is a progressive increase in hardness value (maximum 148 VHN at 130 amp) along the weld zone, which may shows the presence of brittle phase. Further analysis on cracked weld samples revealed the presence of brittle mode of failure in all the weldments except there is combine mode of failure in 100 amps. Thus, from the systematic study, it can be possible to weld the chosen alloys using 100 amps with the utmost care, and futuristic attempts on this can consider by taking suitable filler alloy primarily based on 2nd series of aluminium.