Literature Survey on Diffusivities of Oxygen, Aluminum, and Vanadium in Alpha Titanium, Beta Titanium, and in Rutile
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energy Q of the temperature dependence of diffusivity,
Literature Survey on Diffusivities of Oxygen, Aluminum, and Vanadium in Alpha Titanium, Beta Titanium, and in Rutile
can be obtained. The internal friction method has been used at relatively low temperatures to measure the diffusivity of oxygen. When a stress is applied to a sample along one direction, randomly distributed interstitial solute atoms will tend to move to a position of minimum local strain energy. This is the case whenever the solute atoms (or pairs or clusters of solute atoms) are surrounded by tetragonal strain field. Under oscillating stress condition an internal friction peak occurs at a temperature at which the successful jump frequency of interstitial atoms equals the oscillation frequency. The diffusion coefficient D at this temperature is related to the success jump frequency F by
Z. LIU and G. WELSCH A survey of diffusion data of interstitial oxygen and of the substitutional elements aluminum and vanadium is presented for alpha and beta titanium. It is based on a survey of literature. Oxygen is an important interstitial element in titanium alloys. Oxygen's large chemical affinity to titanium is indicated by T i - - O bond energy of 2.12 eV, ~ comparable to the T i - - T i bond energy of 2.56 eV. 2 Oxygen is difficult to eliminate completely from titanium, and commercial titanium alloys usually contain from 0.10 to 0.20 wt pct oxygen. Oxygen significantly affects the mechanical properties of titanium alloys 1'3 and is sometimes used as an alloY4ing element. The effects of oxygen on phase transformation, .5.6 Youngs modulus, 7'8 hardness, 9'1° fracture toughness, H and other mechanical properties ~2 have been amply documented. Aluminum and vanadium are the most frequently used substitutional alloying elements. Aluminum is an alpha stabilizer and vanadium is a beta stabilizer. The diffusion of oxygen, aluminum, and vanadium plays an important role in the establishment of phase morphologies during heat treatment and processing. The diffusivity of oxygen is also important for the homogenization of oxide films in powder metallurgical compacts, and it affects the thickness of the oxygen-rich alpha scale formed during treatments in oxidizing environment. There exist many investigations of the diffusivities of these elements. However, they are scattered over many journals over a period of more than 30 years. The objective of the present survey was to combine the essential information from these references into an overview for easy comparison. Several methods have been used for oxygen diffusivity measurements, such as internal friction, oxidation, and evaluation of oxygen concentration gradients. For the diffusivities of aluminum and vanadium, the concentration gradient method has been commonly used. Diffusion distances have been measured by metallography, microhardness profile, microprobe analysis, and X-ray analysis, or were indicated by tracer atoms, such as V48.13.J4 The concentration gradient method uses a pair of metal samples of different
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