Preparation and Properties of High Strength Al-Mg-Fe-Mn-Sc-Zr Alloy by Laser Powder Bed Fusion with Quasicrystal Enhancement

Abstract

Submicron dispersoids introduced by microalloying elements are widely used to further improve the strength of solute-strengthened Al-Mg alloys, where quasicrystals, as a special submicron dispersoid, also have a certain dispersion strengthening effect. However, producing quasicrystalline particles in conventional casting processes requires high Fe and Mn additions (> 4 wt.% Fe + Mn), which will decrease ductility and processability. In this research, two different Al-Mg alloys with the same Fe + Mn content but different Fe/Mn ratios were prepared by laser powder bed fusion to investigate the effect of Fe/Mn ratio on the mechanical properties as well as on the formation of quasicrystals. The microscale characterization and tensile test results revealed that the icosahedral quasicrystalline phase was introduced in the alloy with a high Mn content of 1.74 wt.%, while Al2.86(Fe, Mn) phase was observed in the alloy with a high Fe content of 1.59 wt.%. In addition, the high number density quasicrystalline phase had a better ability to hinder the dislocations and pin the grain boundaries, thereby significantly improving the yield strength of the high Mn alloy to 582.3 ± 3.5 MPa. This work can provide new insight into the composition design of additive manufacturing aluminum alloys.

Keywords: Laser powder bed fusion (LPBF), Al-Mg alloys, quasicrystals, Fe/Mn ratio