Abstract: A piece of a titanium-base alloy having an elevated temperature phase transformation is diffusion bonded to a second phase at an accelerated rate or reduced temperature, as compared with conventional diffusion bonding, by manipulating the phase transformation with an alloying element that can be readily introduced into, and removed from, the titanium piece. The introduction of hydrogen into the titanium alloy reduces the temperature of the phase transformation. The titanium alloy can be repeatedly cycled through the phase transformation before or during bonding, by the introduction and removal of hydrogen, to reduce the flow stress through transformation plasticity. Alternatively, the titanium alloy may be loaded with hydrogen to reduce the phase transformation temperature, increasing the fraction of the more deformable phase and then reducing the flow stress of the alloy at the diffusion bonding temperature.

Abstract: The carbon fiber bundles in a carbon-carbon composite are protected against oxidation by coating the fiber bundles with at least one protective layer consisting of an underlayer portion of boron carbide and an overlayer portion of silicon carbide.