The effect of shielding gas on the toughness of ALMg4.5Mn weld metals made by GMAW

Abstract

The effect of MIG/MAG shielding gas on the toughness of aluminium alloy AlMg4.5Mn weld metal has been analysed using the instrumented Charpy pendulum for standard toughness testing. The MIG/MAG welding was performed in the shielded atmosphere of Ar, as well as the mixtures of gases Ar + 0.0307 % O 2, Ar + 30 % He + 0.0317 %O 2 and Ar + 48 % He + 0.0290 % O 2. Metallographic tests have been performed in order to check the appearance and porosity of the weld metal, as well as its toughness testing at different temperatures (20, - 90, - 196 °C), using the instrumental Charpy pendulum, in order to separate the crack initiation and crack growth energy. In this way, a comprehensive insight of the effect of shielding gas on the weld metal toughness has been obtained.