A Study of the Diffusion of Oxygen in α‐Titanium Oxidized in the Temperature Range 460°–700°C

Abstract

the beams with buffered HF increases the maximum free-standing length and eliminates the built-in deflection for beams shorter than Lm. This annealing procedure is sufficient to reflow the phosphosilicate glass layer underneath the poly-Si layer and cause recrystallization of the poly-Si, both of which may help to relax the nonuniform internal stress. Diffusion of phosphorus from the glass into the poly-Si will occur during this relatively severe anneal, which may be undesirable for certain applications. Additional research is needed to determine the minimum temperature and time required for stress relaxation in the poly-Si film. However, beams of useful sizes can be made without any post-deposition treatment of the poly-Si, as is demonstrated in Fig. 4-6. The dynamic properties of poly-Si micromechanical beams are currently being investigated, and the results will be reported later. AcknowledgmentsWe would like to thank Mrs. D. McDaniel for valuable laboratory assistance, and Dr. J. Shott of Stanford Integrated-Circuits Laboratory for use of a CVD oxide reactor.

Isotope effect for diffusion of cobalt in single-crystal α-titanium

“…Note that silver in tin is also a very fast diffuser. According to the previous measurements of diffusivities in a-Ti, the transitionmetal elements, Fey Co and Ni exhibit extremely fast diffusion-much faster than even light interstitial atoms such as carbon (Nakonechnikov andPavlinov 1972: see Dubovtsev, Zotov, Miroshnichenko andNikolayev 1976), nitrogen (Anttila, Raisanen and Keinonen 1983) and oxygen (David, Beranger and Garcia 1983). It is reasonable to suppose that some type of interstitial mechanism is operative (Hood andSchultz 1972, Nakajima et 41.…”

Oxygen diffusion in Ti3Al single crystals

“…The diffusion coefficient of oxygen in -Ti [19][20][21] is smaller than that of Fe [11], Co [12], Cr [13] and Ni [14], but it is larger than the self-diffusivity of Ti [22][23][24]. The trend of impurity diffusivity in Ti 3 Al is qualitatively similar to this trend in -Ti.…”

“…hcp-based D0 19 -type ordered structure of Ti 3 Al and disordered hcp structure of -Ti. Diffusion anisotropy has been the subject of extensive studies on diffusion in -Ti and other metals with a hcp structure.…”

“…Effects of this ordered structure on diffusivity and its anisotropy are of great interest. The preferential site occupation of oxygen atom in the D0 19 -type ordered structure with various interstitial sites having different surrounding atom species may limit diffusivity. In other words, diffusion in Ti 3 Al may exhibit anisotropy owing to the anisotropic atomic arrangement within the structure.…”

A model for experimentally-observed high-strain-rate dynamic strain aging in titanium

“…Among the parameters in the above constitutive relations, the Boltzmann constant k equals 1.38 Â 10 À23 JK À1 , which is a universal constant, the melting temperature of titanium is 1935 K, and the activation energy for the volume diusion of oxygen in titanium is 200 KJ/Mole [19]. The exponents, p and q, are chosen to be the same as those used by Nemat-Nasser and Isaacs [20] and Nemat-Nasser and Li [13] for tantalum and copper, i.e.…”