The effect of high pressure on self-diffusion in beta-titanium

"Diffusion of Ti44 into beta-titanium has been measured as a function of pressure at approximately 10000C using standard lathe-sectioning techniques. The diffusion coefficient is found to decrease with pressure, indicating a positive activation volume. This result is in contradiction of earlier reports of negative activation volumes for diffusion of Fe in S-Ti and U in y-U. The value obtained for the activation volume for self-diffusion in S-Ti is approximately 3.6 ± 1.0 cm3/mOle, corresponding to ~V/VM = 0.33 + 0.1, where VM is the molar volume. Comparison is made with atomic.models and various proposed mechanisms for diffusion in the anomalous body-centered cubic metals. The magnitude of ~V appears to be too large to be consistent with the ""extrinsic"" vacancy mechanism of Kidson, but smaller than would normally be expected for simple vacancy diffusion in bcc metals; It is concluded that diffusion in beta-titanium most probably proceeds via a combination of vacancy and short dislocation-path diffusion, known as the Hart mechanism. Non-gaussian penetration profiles were observed in some of the runs. This has been interpreted in terms of oxide hold-up of the tracer at the surface and possible diffusion of the tracer as an oxide along dislocation pipes or grain boundaries near the surface prior to dissociation."

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year dc:date

1970

Author dc:creator

• Jeffery, Rondo Nelden

Contributors dc:contributor

• Lazarus, David

• high pressure
• self-diffusion
• beta-titanium
• lathe-sectioning technique

Statement dc:rights

• 1970 Rondo Nelden Jeffery

Language dc:language

en

Identifier

6053442

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/25850