Fracture mechanism of 316L/BNi-2 brazed joints using experiment and microstructure-based model

Compact components are prone to failure at brazed joints. To ensure the reliability of brazed joints, it is vital to have a comprehensive understanding of the fracture mechanism of brazed joints which can be attributed to highly inhomogeneous microstructures and individual phase mechanical properties. This study measured the stress-strain curve of brazed joint micro-zone of 316L austenitic stainless steel with the BNi-2 filler alloy by a tensile testing machine equipped with a CCD camera. The instrumented indentation technique was used to determine the flow properties of individual phases in joints considering the size effect. Representative volume element (RVE) technology was applied to simulate the mechanical behavior of brazed joints, which was in good agreement with the tested. The fracture of brazed joints can be divided into ductile fracture and brittle fracture which includes the decohesion of the interface between the boride and the austenite matrix and the fragmentation of the boride in terms of the analysis of the morphology of cross-section and fracture surface in brazed joints. According to the stress and strain distribution in the brazing micro-zone, the plastic strain localization cause decohesion, and the stress concentration along the loading direction cause boride fragmentation.