Work

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

Year: 2024

Type: article

Abstract: The low laser absorption rate, poor powder fluidity, and high thermal conductivity of 7075 aluminum alloy leads to parts produced using Laser powder bed fusion (L-PBF) technology having an undesirable microstructure. This is characterized by coarse columnar crystals and severe hot cracks, making it challenging to meet mechanical and corrosion resistance standards. Grain refinement has been identified as an effective solution to this issue, often achieved by incorporating nucleating agents or elements with high grain growth limiting factors (Q-values) in the additive manufacturing process. In this study, a 2 wt% micron-sized TC4 alloy powder was mechanically mixed into 7075 Al alloy powder to utilize the high Q values of Ti and V elements in TC4. Subsequently, L-PBF technology was employed to fabricate aluminum alloys with fine equiaxed grains. The resulting alloy sample exhibited no cracks and had an average grain size of 2.0158 nm. During solidification, Al3Ti cubic particles were formed in situ, acting as heterogeneous nucleation sites and contributing to grain refinement. The mechanical properties of the alloy were notably enhanced, with the ultimate tensile strength and elongation at break reaching 369.204 MPa and 9.371% respectively - representing a more than 9 times increase compared to L-PBFed 7075 Al alloy. Moreover, the corrosion resistance of the alloy significantly improved, as evidenced by the decrease in corrosion current density from 9.0964E-06 to 2.0887E-06. These enhancements can be primarily attributed to grain refinement and the increase in precipitated phases. This approach could be extended to other low weldability high-strength aluminum alloys.

Source: Journal of Materials Research and Technology

DOI: 10.1016/j.jmrt.2024.10.170