Fracture Behavior of AlMg4.5Mn Weld Metal at Different Temperatures under Impact Loading

This paper deals with a three-component aluminum alloy AlMg4.5Mn that was welded using a GTAW process in the shielded atmosphere of Ar+70%He+0.015%N-2. The weld-metal toughness was evaluated at three different temperatures using instrumental Charpy pendulum impact testing to measure not only the total energy, but also the crack initiation energy and the crack growth energy. Fractographic analysis of the fracture surfaces and EDS analysis of large second-phase particles on fractured surfaces at each temperature were also carried out. Fractographic analysis at different temperatures indicated a clearly distinguishable fracture mechanism. It was inferred that the absorbed energy was closely correlated with the fracturing of surfaces. Moreover, it was concluded that with decrease in the amount of microscopic voids and dimples, the total energy absorbed also decreased.