Diffusion of oxygen in vanadium and its alloys

Abstract

Diffusion coefficients of oxygen have been measured in vanadium and dilute substitutional alloys (V-1Si, V-0·-1Al, V-0·-1B, V-5Cr, V-5Fe, V-5Mo, V-5Nb, V-5Ti and V-3Ti-2Si where the compositions are in approximate atomic per cent) over the temperature range 489–774 K. The ¹⁶O was injected by ion implantation. The diffusion penetration profiles were measured by the ¹⁶O(d,p)^17•O nuclear reaction method. The temperature dependence of the oxygen diffusivity in vanadium is expressed as

The addition of silicon and aluminium hardly affects oxygen diffusion, while the addition of iron, niobium and boron decreases the diffusivity by 20–70%, and the addition of chromium and molybdenum decreases the activation energy by 10–15%. The most significant alloying effect is observed in V-3Ti-2Si and V-5Ti alloys. The diffusivity in V-5Ti alloy is about two orders of magnitude lower than that in vanadium. This effect is interpreted as evidence for a trapping effect due to titanium; the binding energy is estimated to be about 52 kJ mol⁻¹.