sLow cycle fatigue properties of a 9–12% Cr martensitic steel welded joint with Ni-based weld metal based on a local strain approach

• A local strain approach considering mechanical heterogeneity of welded joints is proposed. • The LCF properties of the material in the softened zone of the welded joint of the 9–12% Cr martensitic steel welded joint with Ni-based weld metal are accurately evaluated by the local strain approach considering mechanical heterogeneity. • The LCF properties of the HAZ are obtained through hourglass specimens based on the local strain approach. The effect of mechanical heterogeneity on the low cycle fatigue (LCF) properties of a 9–12% Cr martensitic steel welded joint with Ni-based weld metal are studied using smooth and hourglass specimens based on a local strain approach. The results indicate that the smooth specimens of the welded joint fracture at the softened weld metal (WM) due to the strain concentration. Moreover, the strain–life curves of the smooth specimens of the welded joint are close to the strain–life curves of the WM smooth specimens after the local strain approach considering the mechanical heterogeneity of welded joints is adopted. The LCF properties of the inter-critically heat-affected zone (ICHAZ) are obtained through hourglass specimens based on the local strain approach. The LCF properties of the base metal (BM), WM, and ICHAZ in the welded joint are compared to investigate the relationships of the LCF properties of the welded joint and different microzones.