Role of Er on the densification, microstructure and mechanical properties of 7075 aluminium alloys manufactured by laser powder bed fusion

Abstract

Fabricating crack-free 7075 aluminium alloy by laser powder bed fusion (LPBF) is currently a hot research topic. In this work, pre-alloyed 7075Al + Er powder was prepared, and crack-free samples were printed by LPBF by adjusting the process parameters. Furthermore, the influence of process parameters and the mechanism of crack inhibition by Er were discussed. Er can generate Al3Er coherent with the Al matrix, which has the grain refinement effect, shortens the length of columnar crystals from 106 μm to 84 μm and is conducive to the dispersion and further solidification of the liquid film in the paste solidification stage. Al3Er also reduces the texture strength and makes the thermal stress more uniform. The final measured tensile strength of the printed sample was 338 MPa, and the elongation was 15.9%, which was 32% and 74.7% higher than those of the 7075Al samples without Er addition, respectively. In this work, the effect of rare earth element Er on the improvement of the printability and crack suppression of 7075 aluminium alloy by laser powder bed fusion was discussed, which provides experimental support for crack-free additive manufacturing and application of high-strength aluminium alloys.

Keywords

• Laser powder bed fusion (LPBF)
• 7××× series aluminium alloys
• Rare earth element Er
• Microstructure
• Nucleation