Fatigue crack growth and fracture toughness characteristics within subzones of Al-Mg-Si joints

This study comparatively analyzed the fatigue crack growth rates (FCGR) and fracture toughness (FT) across different subzones of Al-Mg-Si alloy joints with a plate thickness of 20 mm, using experimental tests, The FCGR results were further validated through FRANC3D simulations. The finding indicate that the WM exhibits the highest FCGR, followed by the HAZ, while the BM exhibits superior fatigue resistance in both FCGR and FT. The FT of the WM slightly exceeds that of the HAZ, as the latter experiences strength and ductility degradation caused by precipitate coarsening. This results clearly reveals the disparities in fracture mechanical properties across different subzones. During the final fracture stage, the HAZ shows negligible deflection due to its weaker mechanical properties, while the BM displays significant deflection (44°). In contrast, the WM exhibits constrained deflection (23°), resulting from constrained crack propagation within the HAZ and WM regions. This substantial difference provides a basis for determining the crack growth path. Finally, the study, employing the critical toughness model, predicts the FT of different subzones under plane strain conditions, thereby contributing valuable data for predicting the fatigue crack growth life of aluminum alloy joints.