C. S. Chang, Engineered Materials Solutions, Attleboro, MA; C. T. Chang, National Dong Hwa University, Shoufeng, Hualien, Taiwan; R. K. Shiue, National Taiwan University, Taipei, Taiwan
Microstructural observations of infrared brazed Ti-15-3 joint using Ti-15Cu-15Ni and Ti-15Cu-25Ni braze alloys have been performed. Ti-rich phase alloyed with higher Cu, Ni contents, Ti-rich phase alloyed with lower contents of Cu and Ni, eutectic and eutectoid structure are observed in the as brazed specimen. Interdiffusion among V, Cr, Cu and Ni is preceded during annealing the joint at different temperatures and/or time periods. Accordingly, it is preferred to apply appropriate brazing cycle in order to reduce or eliminate the presence of residual Cu-Ni rich Ti phase in brazing titanium alloys using Ti-Cu-Ni filler metals.
Summary: In this presentation, Ti-Cu-Ni foils produced by a cold, roll-bonding process, will be demonstrated in two commercially available compositions (Ti-15Cu-15Ni and Ti-15Cu-25Ni). The foil is a multi-layered composite that consists of Ti, Cu and Ni individual components. The microstructures of braze joints will be characterized to identify the solidification paths. The brazing conditions as well as post-brazing heat treatment were varied to rationalize the process windows for optimum joint properties. The shear strength of braze joints is strongly affected by the presence of solidification phases although they can be readily mitigated by selecting proper time and temperature parameters. Additional examples of other Ti-based braze filler will also be presented.
