Effect of pulsed metal inert gas (pulsed-MIG) and cold metal transfer (CMT) techniques on hydrogen dissolution in wire arc additive manufacturing (WAAM) of aluminium

Aluminium is one of the most experimented metals in the WAAM field owing to a wide range of applications in the automotive sector. Due to concerns over reduction of strength, elimination of porosity from wire arc additive manufactured aluminium is one of the major challenges. In line with this, the current investigation presents findings on hydrogen dissolution in solid aluminium and hydrogen consumed to form porosity along with its distribution as a function of heat inputs and interlayer temperatures in a WAAM 5183 aluminium alloy. Two varieties of WAAM, pulsed metal inert gas (MIG) and cold metal transfer (CMT) were explored. Samples made with pulsed metal inert gas (pulsed MIG) process picked up more hydrogen compared to samples produced by cold metal transfer technique. Correspondingly, pulsed MIG samples showed increased number of pores and volume fraction of porosity than samples manufactured using the cold metal transfer (CMT) technique for different heat input and interlayer temperature conditions. However, CMT samples exhibited higher amount of dissolved hydrogen in solid solution compared to pulsed MIG process. In addition, heat input, interlayer temperature and interlayer dwell time also played a key role in pore formation and distribution in WAAM produced aluminium 5183 alloy.