Ultrasonic Evaluation of Titanium Alloy Diffusion Bonding

During the diffusion bond process, parts are heated to about one half the absolute melting point, pressed together at a stress below the macroscopic yield stress, and conditions maintained for a specified time. Bonding proceeds through three steps: local yielding of contact points upon initial application of stress; creep deformation on the bonding plane to yield discontinuous voids; and closure of voids by vacancy diffusion. Presently, nondestructive evaluation emphasizes detection of residual unbonds and voids, from incomplete void isolation or closure.</p