Study on the brazing process of TC4 titanium alloy/304 stainless steel and the effect of gap on braze joint performance
摘要
The joining of titanium alloys and stainless steels is critically required in aerospace and other fields, frequently accomplished through brazing. This paper investigates vacuum brazing of TC4 titanium alloy and 304 stainless steel using Ag70-Cu26-Ti4 filler metal. Through SEM/EDS, XRD characterization, and shear tests, the effects of process parameters on interfacial microstructure evolution and mechanical properties were analyzed. The filler metal’s fluidity at different gaps and its impact on joint strength were examined. Results demonstrate that the joint achieved optimal shear strength of 191 MPa at 830 °C/5 min, with appropriate reaction layer thickness and dispersed brittle Cu-Ti phases. Elevated temperature caused Cu-Ti phase coarsening throughout the brazing seam, reducing strength. At 0.21 mm gap, the filler metal showed optimum fluidity with 31 mm filling distance, yielding maximum shear strength of 127 MPa at 850 °C/5 min. Reaction layer growth kinetics revealed activation energies of 111.0 kJ·mol⁻1 in Zone III (TC4 side) and 244.5 kJ·mol⁻1 in Zone I (stainless steel side), confirming easier diffusion of Cu and Ti atoms in the titanium alloy. This study provides theoretical guidance for suppressing brittle phase formation and optimizing brazing gap design.