Enhanced Fatigue Resistance of Nano-Treated 2024 Aluminum Alloy via Laser Powder-Bed Fusion

Fatigue performance remains a major barrier to the deployment of laser powder-bed fusion (LPBF) high-strength aluminum alloys, because cyclic loading amplifies the detrimental effects of residual porosity and microstructural heterogeneity. Here, we investigate the long-term fatigue behavior of nano-treated LPBF AA2024 (2024NT), with and without hot isostatic pressing (HIP), to clarify how nano-treating and residual porosity jointly govern cyclic durability. The 2024NT alloy exhibited fatigue resistance superior to most reported LPBF aluminum alloys, while HIP further enhance the run-out stress levels up to ∼200 MPa and a fatigue strength approaching ∼50% of yield strength. Defect-tolerance analysis further indicates an effective critical pore size of ∼80–100 μm, substantially larger than that typically reported for conventional LPBF aluminum alloys. This enhanced tolerance arises from two coupled mechanisms: a refined, homogeneous microstructure with dispersed TiC nanoparticles that promotes tortuous, energy-dissipative crack paths, and TiC pseudo-clusters around pores that act as local high-modulus barriers to crack initiation and short-crack growth. These results demonstrate that nano-treating, particularly when combined with porosity mitigation postprocessing, provides an effective pathway to achieve fatigue performance in LPBF wrought aluminum alloys approaching or exceeding wrought benchmarks.