Electrolytic Hydrogen in Beta Titanium.
NAVAL AIR DEVELOPMENT CENTER WARMINSTER PA AIR VEHICLE TECHNOLOGY DEPT
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The vacuum processes of ion bombardment etching followed by thin film vapor deposition of palladium have been employed to produce oxide-free titanium specimens suitable for electrochemical hydrogen permeation and embrittlement studies. The alloy chosen for study was Ti - 11.5 Mo - 6 Zr - 4.5 Sn in the solution treated and quenched condition. Electrochemical permeation experiments which were conducted with basic solutions containing cyanide additions exhibited well behaved hydrogen permeation transientes corresponding to simple diffusion behavior. These experiments yielded a diffusivity at 21 C for hydrogen through the beta alloy of 5.6 or - 1.92 X 10 sq cmsec. Anomalous permeation behavior occurred when high hydrogen chemical potentials associated with acidic and basic solutions without cyanide, existed at the input side during charging. The anomalous behavior occurs at the later stages of the approach to steady state. This behavior is shown to be consistent with the trapping model of hydrogen in metals of McNabb and Foster. Plastic deformation and spontaneous cracking at the wetted portion of the specimen have been observed under extreme conditions during this anomalous behavior. A substantial part of the deformation is found to be reversible i.e., interstitial or trapped hydrogen atoms diffuse out of the metal upon heating or standing. A series of mandrel bend experiments were performed to further define the embrittlement phenomenon.
- Properties of Metals and Alloys