In-situ microalloying of Al-Cu-Sc alloy manufactured by beam oscillating wire laser directed energy deposition: Grain refinement and properties improvement

Abstract

Al-Cu alloys manufactured by wire laser directed energy deposition (WLDED) usually exist coarse columnar grains. The novelty of this study is adding Sc to Al-Cu alloy of beam oscillation wire laser directed energy deposition (O-WLDED), achieving grain refinement by in-situ microalloying of Sc. An Al-Cu alloy part and an Al-Cu-Sc alloy part are prepared by O-WLDED, respectively. Furthermore, how the Sc affects the microstructure and mechanical properties is explored and discussed. The in-situ microalloying of Sc provides more nucleation sites for grains and promotes the columnar to equiaxed transformation. The average grain size of the overlapping zone decreases from 21.64 to 14.32 μm, and that of the remelting zone decreases from 18.67 to 7.83 μm. The grain refinement is significant. The contents of θ-Al2Cu and θ'-Al2Cu at grain boundaries of the Al-Cu-Sc alloy reduce since Al3Sc particles precipitated from the Al matrix can hinder the segregation of Cu. The ultimate tensile strength and elongation of the Al-Cu-Sc alloy reach 433 MPa and 11.8 %, respectively, respectively 117 MPa and 2.6 % higher than those of the Al-Cu alloy.