Loss of elemental Mg during wire + arc additive manufacturing of Al-Mg alloy and its effect on mechanical properties

Abstract

Elemental Mg is easily evaporated or burnt during welding or wire + arc additive manufacturing (WAAM), and results in a fluctuation of the composition and mechanical performances. Elemental Mg loss during the WAAM of Al–Mg alloy was investigated and the effect of Mg loss on the mechanical properties was discussed based on results from the chemical composition measurement and mechanical properties test. The loss of elemental Mg was non-negligible because of remelting during WAAM, and the loss rate of elemental Mg increased with an increase in current and decreased with an increase in travel speed. The elemental Mg distribution in the WAAM component was uniform, but obvious element enrichment occurred near the fusion zone of the substrate. With an increase in the loss rate of elemental Mg, the tensile strength and average hardness of the WAAM component decreased, whereas the elongation increased. During the WAAM of the Al–Mg alloy, with an increase in the Mg loss rate, the lattice parameters decreased because the solid solubility decreased in the Al matrix during the WAAM.