Pressure dependence of Zr diffusion in the equiatomic B.C.C. TiZr alloy

Positive as well as negative activation volumes have been measured in the past for self‐diffusion in “anomalous” b.c.c. metals. To contribute to this problem and to obtain further information on the diffusion mechanism in b.c.c. transition metals the pressure dependence of diffusion of 95 Zr is measured in the equiatomic b.c.c. TiZr alloy at 1003 and 1493 K in the pressure range up to 14.4 × 10 8 Pa. The rather small but positive activation volumes Δ V = 0.31 ± 0.06Ω and Δ V = 0.35 ± 0.10Ω, respectively, are obtained. The results are in conflict with negative Δ V values reported for this alloy by Smirnov et al., however, they agree very well with Δ V of self‐diffusion in β‐Ti. Within the limits of error Δ V is independent of temperature which indicates that only one diffusion mechanism is operating despite of the strongly curved Arrhenius relations of 95 Zr and 44 Ti diffusion in TiZr alloy. The present results confirm a monovacancy mechanism in group IVA b.c.c. metals.