Evaluation of the microstructure related strength of CrMoV weldment by using the in-situ tensile test of miniature specimen

The evolution of grain size and structure morphology across the CrMoV welded joint were investigated. The tensile properties of subzones in the weldment were measured by miniature specimens. And the measured results were compared to the results acquired from the standard round bar specimen. It is found that the strength characterized by miniature specimen is lower than that obtained by standard specimen. The deviation of strength is acceptable. However, the measured Young's modulus is not consistent with the elastic modulus of standard specimen, due to the jig deformation and clamped effects of the miniature specimen. Although HAZ is the weakest location due to the deteriorated microstructure and the reduced strength, the failure pattern is different comparing the measured results of the miniature specimen and that of the standard round bar cross-weld specimen. For the miniature specimen, fracture occurred at the HAZ region close to the base metal (BM). However, the fracture of the standard specimen occurred in the BM instead of the HAZ region. The difference is ascribed to the different constraints of specimens with various geometric dimension.