Microstructure evolution and interfacial failure mechanism in 316LSS diffusion-bonded joints

Microscopic tensile test was conducted on 316LSS vacuum diffusion-bonded joints to investigate the microstructure evolution and effect of micro-voids on interfacial failure mechanism. In situ observation of the interfacial crack initiation and propagation was carried out during the whole testing. The results showed that the most likely sites for cracks initiation are grain boundaries. The favorable grain boundaries containing cracks are oriented at 0–20° to the loading axis. Intergranular cracks play a dominant role in interfacial failure. Micro-voids do not link up each other until the load is increased to 352 MPa (63% σb). For 316LSS diffusion-bonded joints, interfacial failure depends mainly on microstructure of joints.