Enhancing the mechanical properties of 304 stainless steel brazed joint through thermomechanical treatment

This paper investigates the effect of thermomechanical treatment (TMT) on the microstructure and mechanical properties of 304 stainless steel brazed joints. A comparative analysis was performed on the microstructural characteristics and performance variations among as-brazed (AB) joints, heat-treated (HT) joints, deformation-processed (DP) joints, and thermomechanical-treated (TMT) joints. The results demonstrate that the microstructure of the as-brazed joint features an island-like, supersaturated Cu-based solid solution, an Ag-Cu-β ternary eutectic structure, and an Ag-based solid solution matrix. Following thermomechanical treatment, the Cu-rich phase content in the brazing seam increased and became elongated in the deformation direction, while there was a notable decrease in the content of the Ag-rich phase and the eutectic structure. Under 40% strain, the joint's shear strength achieved 309 MPa, and the microhardness rose to 173 HV, reflecting enhancements of 10% and 21.8%, respectively, compared to the as-brazed condition. This increase in strength mainly results from the combined effects of dislocation strengthening and solid solution strengthening. • The effects of TMT on the microstructure and properties of braze joints were studied for the first time. • The TMT process (40% strain + 500 °C/2 hours annealing) increases the shear strength of brazed joints by 10%. • TMT enhances the content of Cu-rich phases in the brazing seam and improves interfacial diffusion.