Effect of Pressure on the Mobility of Interstitial Oxygen and Nitrogen in Vanadium

Abstract

Measurements of stress relaxation as a function of hydrostatic pressure up to 9000 kg/${\mathrm{cm}}^2$ have been made on a vanadium sample containing approximately 0.1 atomic percent dissolved oxygen and 0.2 atomic percent dissolved nitrogen. In the temperature range 83.0° to 98.0°C, the relaxation time due to dissolved oxygen is found to increase exponentially with pressure, the value at 9000 kg/${\mathrm{cm}}^2$ being about 1.7 times the value at 1 kg/${\mathrm{cm}}^2$. The pressure dependence of the stress relaxation can be interpreted in terms of an activation volume of 1.7 ${\mathrm{cm}}^3$/mole which is about equal to the molar volume of the diffusing oxygen atoms. The relaxation times due to the dissolved nitrogen have been measured at 156.8°C and 163.0°C. The values at 9000 kg/${\mathrm{cm}}^2$ are about 1.3 times the values at 1 kg/${\mathrm{cm}}^2$, the activation volume being about 1.1 ${\mathrm{cm}}^3$/mole.