Laser powder bed fusion of a novel crack-free Al-Mg-Sc-Zr alloy: Printability, microstructure characterization and mechanical performance

Abstract

Laser powder bed fusion (LPBF) of aluminum alloys has gained wide interest in recent years, the focus of research is gradually transferringg from processing attempts on conventional castable aluminum alloys to exploiting new aluminum alloy systems. In the present work, a novel crack-free AlMgScZr alloy was prepared by LPBF. The laser printability, microstructure evolution, and mechanical performance of this novel AlMgScZr alloy were investigated. A near fully equiaxed ultrafine grain structure instead of typical coarse columnar grain domains was acquired. The cracks were significantly eliminated after ScH3 and ZrH2 synergetic modification due to grain refinement. The in-situ formation of Al3(Sc, Zr) nano-precipitates can act as the nuclei of α-Al, promoting grain refinement and improving mechanical performance. This ultrafine equiaxed microstructure resulted in an outstanding tensile strength of 451 MPa along with an exceptional fracture elongation of 15.1%. These tensile performance are comparable to those of conventional LPBF fabricated Al alloys. The findings in this work highlight a new strategy to enhance the laser printability and mechanical properties of high strength Al alloys and other hard-printing lightweight materials.