Laser powder bed fusion of high solute Al-Zn-Mg alloys: Processing, characterisation and properties

Additive manufacturing of aluminium alloys by laser powder bed fusion (LPBF) has been notionally restricted to a small number of alloy compositions to avoid hot cracking and excessive porosity. In the present work, three unique alloy compositions from the Al-Zn-Mg system with high solute content (Zn > 10 wt% and Mg > 2 wt%) were designed in pursuit of attaining high strength from directly LPBF prepared Al-alloys. The high solute alloys were successfully fabricated, and in-depth microstructural characterisation and phase identification revealed the presence of a new quasicrystalline phase, which was named P-phase. The hardness of the alloys were higher than the existing as-fabricated Al-Zn-Mg alloys and comparable to conventionally fabricated high strength wrought aluminium alloys, however, the as-built tensile properties revealed brittleness. This study presents an insight into the possibilities of fabricating high strength Al-Zn-Mg alloys without expensive additions such as Sc or Zr, through selective laser melting.