Superior mechanical properties and corrosion resistance of laser powder bed fusion 7075 Al/TC4 alloy through microstructure design

Abstract

The 7075 Al alloy fabricated using laser powder bed fusion (L-PBF) technology exhibits coarse columnar grains and significant thermal cracking, which hinders it from meeting mechanical and corrosion resistance standards. In this study, 2 wt% micron-sized the Ti6Al4V (TC4) powder was mechanically mixed into 7075 Al alloy powder, resulting in the fabrication of an Al alloy characterized by fine equiaxed grains through the L-PBF process. The resulting alloy sample exhibited no cracks, with an average grain size of 2.016 nm. During solidification, Al3Ti cubic particles formed in situ, serving as heterogeneous nucleation sites, while the Ti element, which possesses a high growth limiting factor (Q value), further facilitates the heterogeneous nucleation of grains. The mechanical properties of the alloy were significantly improved, achieving an ultimate tensile strength of 369.204 MPa and an elongation at break of 9.371%, which is more than nine times greater than that of the L-PBF 7075 Al alloy. Furthermore, the corrosion current density decreased from 9.096E-06 to 2.089E-06, indicating a marked enhancement in the alloy's corrosion resistance. This method has the potential to be applied to the L-PBF of other low-weldability, high-strength Al alloys, thereby laying the groundwork for expanding the industrial applications of L-PBF.

Keywords

• Additive manufacturing
• 7075 Al alloy
• Grain refinement
• Mechanical property
• Corrosion resisting property