Structures and properties of titanium matrix composite joints

A rapid infrared transient liquid phase joining process has been developed for the joining of titanium matrix composites. Using this technique, composites were joined at low cost and in a fraction of the time typically taken by conventional vacuum brazing. The process also does not require any vacuum or high pressure. The joints produced by this technique have joint shear strengths comparable to the interlaminar shear strength of the SCS-6/{dollar}beta{dollar}21S composite and does not degrade the composite mechanical properties. High temperature testing at 815{dollar}spcirc{dollar}C reveals that failure occurs at the first row of (0{dollar}spcirc{dollar}) fibers and not in the joint.; Two models were utilized in this study to outline the possible optimum joining parameters. The joint evolution during transient liquid phase joining was modeled using a thin film diffusion model in conjunction with the Ti-Cu binary phase diagram. This was used to predict the time for isothermal solidification and homogenization of the joint at a given temperature. The fiber reaction zone growth kinetics was modeled with a parabolic growth law. It was found through the use of the two models that joining for short times at higher temperatures was most effective in producing homogenized joints with minimal fiber reaction zone growth.; Joining experiments were performed utilizing the parameters outlined by the thin film diffusion model and fiber reaction zone growth model. It was observed that the experimental and calculated values of time for isothermal solidification and homogenization of the joint at the joining temperature agreed reasonably well. The resultant fiber reaction zone growth during joining also agreed reasonably well with predicted values.; Due to the fast cooling of the infrared processing technique, it was also observed that post heat treatment on the composite material was not necessary to suppress the formation of a deleterious {dollar}omega{dollar} phase during subsequent uses at intermediate temperatures for times up to ten hours. This cooling rate phenomenon was explained in terms of the pre-existing athermal {dollar}omega{dollar} phase formed during cooling from the joining temperature.