Effect of Zn content on the formability and aging precipitation of Al–Zn–Mg–Cu–Nb alloys prepared by LPBF

Abstract

In this work, the effect of Zn content on the formability and aging precipitation of Al–Zn–Mg–Cu–Nb alloys prepared by laser powder bed fusion (LPBF) were investigated via experiments and in-depth characterization. Results show that the increase in Zn content narrows the LPBF processing window, owing to the significant evaporation of Zn element during LPBF. The increase of Zn content not only accelerates the aging kinetics of Al–Zn–Mg–Cu–Nb alloys, but also increases the number density of nanoprecipitates and reduces the PFZ width, resulting in an enhancement in the peak microhardness. The microstructure evolution and aging behavior of alloys during direct aging (DA) and traditional solution treatment and aging (STA) were compared. DA can maintain fine equiaxed grains, while a bimodal grain structure with coarse and fine grains can be obtained after STA. The peak microhardness and the number density of nanoprecipitates in alloys treated with STA is higher than that of alloys treated with DA, which indicates that the traditional STA heat treatment is still applicable to Al–Zn–Mg–Cu–Nb alloys fabricated by LPBF.

Keywords

• Laser powder bed fusion (LPBF)
• Al–Zn–Mg–Cu alloy
• High Zn content
• Element evaporation
• Heat treatment
• Aging precipitation