Improved fatigue properties of laser powder bed fusion of Al–4.74Mg–0.70Sc–0.32Zr alloy via hot isostatic pressing

Laser powder bed fusion (L-PBF) processed components usually exhibit reduced fatigue performance owing to unavoidable defects at multiple scales, especially when the loading direction is parallel to the building direction. In this study, hot isostatic pressing (HIP) was applied to the L-PBFed Al-4.74Mg-0.70Sc-0.32Zr (wt.%) alloy to enhance the fatigue properties with a focus on the defect (porosities and inclusions) effects, compared with the direct-aged samples. The results demonstrated that HIP induced inconspicuous microstructural effects, but it healed the porosities and promoted oxidation. Therefore, the fatigue crack initiation transformed the oxide-associated porosity into an oxide, with a significant fatigue strength improvement.