C. T. Chang, National Dong Hwa University, Shoufeng, Hualien, Taiwan; R. K. Shiue, National Taiwan University, Taipei, Taiwan; C. S. Chang, Engineered Materials Solutions, Attleboro, MA

Summary: Joining of high strength Ti alloys by TiCuNi type brazing foils in an infrared furnace was conducted to evaluate the effects of time and temperature on the braze joint microstructure and fracture behaviors. Braze joint consisted initially of two phases, a Ti-rich matrix and a Cu-Ni rich Ti phase. Either a longer holding time or higher brazing temperatures reduced the Cu-Ni rich Ti phase, which eventually dissolve into the matrix. By reducing the amount of Cu-Ni rich Ti phase in the braze joint the shear strength increased and fracture morphology changed from brittle cleavage to ductile dimple type. A diffusion model will be presented, which predict the presence of Cu-Ni rich Ti phase in the braze joints and showed good agreement with experimental observations. This model will be useful to design the brazing process for optimized braze joint properties.