The dependence of microstructure and mechanical properties on substrate heat treatment in AlN ceramics/AgCuTi/316 stainless steel brazed joints

Abstract

The residual stress is the main technical challenge for ceramics/metal brazing, and the previous solutions are complicated. To eliminate the residual stress, the effects of substrate heat treatment on microstructures and properties were investigated in AlN ceramics/AgCuTi/316 stainless steel brazed joints. At 900 °C brazing for 5 min, the AlN/as-received 316 joint had the highest strength at 223 MPa, and the maximum residual stress on the metal side reached 1.1 GPa. After the substrate solution treatment, the maximum residual stress decreased by 45%, and the shear strength increased to 262 MPa. The residual stress increased and the shear strength decreased in the AlN/stress-relief annealed 316 brazed joint. The substrate heat treatment influences the interdiffusion between the substrate and the filler metal by adjusting the grain size and the stress state in the substrate, thus changing the content and distribution of brittle phases (such as TiFe and TiFe2) in the brazed joint. As a result, the substrate heat treatment can improve the shear strength by changing the residual stress in the brazed joint, which is of great significance for improving the quality of ceramics/metal brazing.