Prediction of low-cycle fatigue properties of additive manufactured IN718 by crystal plasticity modelling incorporating effects from crystallographic orientations and defects

In this work, wire arc additive manufactured IN718 materials with different textures and defect characteristics were obtained via two deposition strategies: parallel mode (P_mode) and oscillation mode (O_mode). The influences of these microstructure variables on the low-cycle fatigue (LCF) properties were systematically investigated by experimental and crystal plasticity finite element (CPFE) frameworks. Results revealed that the weak texture of the O_mode sample may be detrimental to LCF due to strain incompatibility between adjacent grains. However, large-sized pore defects in the P_mode samples significantly increased the dispersity of LCF life. The sensitivity of fatigue crack initiation to critical defect size and location was further accurately captured based on the stored energy density criterion, and the fatigue crack nucleation life was also quantified. Finally, the LCF limit was calculated based on the Coffin-Manson equation, and the life prediction intervals of WAAMed-IN718 alloys with different deposition strategies were unified.