Low-Cycle Fatigue Properties of Ti6Al4V Laser-Welded Joints Based on a Local Strain Approach

The low-cycle fatigue (LCF) properties of Ti6Al4V and laser-welded joints with different welding speeds are studied using smooth and notched flat specimens. A local strain approach is proposed to estimate the LCF properties of the notched flat specimen based on elastic–plastic finite element analysis (EPFEA). The local strain used in the approach is defined as the average strain in the plastic zone at the notch root and critical section of the notched flat specimen. The results indicate that the local strain approach is suitable for estimating the LCF properties of the notched flat Ti6Al4V titanium alloy specimen. The stress–strain relationship derived from the microhardness can be used in the EPFEA. The LCF properties of the Ti6Al4V laser-welded joints are worse in the heat-affected zone (HAZ) than in the base metal (BM) due to the martensite structure in the HAZ and the mechanical heterogeneity in the welded joints. The LCF properties of the Ti6Al4V laser-welded joints with different welding speeds are close under low strain levels and worse with higher welding speeds under high strain levels.