Titanium diffusion bond evaluation via acoustic microscopy

The author utilized 200 MHz Rayleigh waves to perform the nondestructive evaluation of a titanium diffusion-bonded specimen, using both the imaging and metrology modes of the acoustic microscope. Optical inspection of the joint required chemical etching to reveal the oxygen-rich α-phase of the bonded region. Acoustic images of high contrast, as well as Rayleigh velocities inside and without the joint region (11% difference), were readily obtained on the as-polished surface. The results are interpreted and the implications for applications discussed. It is concluded that the acoustic microscope study has shown that diffusion-bonded regions in titanium may be identified and imaged with large contrast and good gray scale. The region of the diffusion bond stands out significantly from the surrounding bulk, adjacent to the bond plane