Low-cycle Fatigue Life Prediction of LPBF GH4169 via Crystal Plasticity: The Dominant Role of Porosity Defects

Abstract

Most GH4169 components serve in harsh environments where low-cycle fatigue (LCF) performance is critical. However, accurate LCF life prediction for laser powder bed fusion (LPBF) components remains challenging due to the complex coupling of heterogeneous microstructures and process-induced porosity defects. Existing studies routinely idealize porosity defects as simplified geometric primitives, overlooking the decisive role of its realistic morphology in damage evolution. To address this issue, the present work fabricated samples with different defect distribution patterns (lack-of-fusion (LoF) dominated and gas pore dominated) via manipulating the process parameters of LPBF. An orthogonal numerical experiment was performed to decouple the effects of defect size and morphology via crystal plasticity finite element (CPFE) method. Building on this mechanistic insight, a CPFE framework incorporating high-fidelity defect geometries was established, with stored energy density (SED) as the fatigue indicator parameter. The framework delivered accurate LCF life predictions for high-density samples across the full strain amplitude range (0.4%–1.2%). For low-density samples, prediction accuracy was maintained at low strain amplitudes (≤ 0.6%), whereas deviations occurred at high strain amplitudes (≥ 0.6%). Incorporating the actual largest defect into the RVE confirmed that insufficient sampling of extreme defects was a major cause of the observed prediction deviations. Additionally, specific continuously distributed porosity defects were found to form interconnected damage bands that accelerate microcrack coalescence. This work establishes a robust pathway for reliable LCF life prediction in LPBF GH4169 components with diverse porosity defect distribution patterns.