Abstract: Investigations on the fabrication of large-size lightweight Mg alloy components by wire-arc directed energy deposition (DED) are steadily flourishing. Nevertheless, most of these components still suffer from inferior performance due to internal defects and inherent columnar grains. Herein, external ultrasound fields with different powers were successfully introduced into the wire-arc DED of AZ31 Mg alloy. The microstructure, defects, and mechanical properties of the fabricated components were carefully characterized and compared. The results show that the external ultrasound fields lead to decreased porosity, complete columnar to equiaxed transition (CET), and enhanced performance. Consequently, the UA90 samples exhibited a remarkable increase of ∼30%, ∼45%, and ∼189% in yield strength, ultimate tensile strength, and elongation, respectively. The dominant mechanisms of enhanced strength-ductility synergy were analyzed in detail. This study thus sheds new light on wire-arc DED of Mg alloy components with excellent performance via external ultrasound fields.

Key words: Wire-arc directed energy deposition, External ultrasound field, Defects, Microstructure evolution, Strength-ductility synergy