Pressure dependence of self-diffusion in B2 intermetallic phases

Pressure dependence of volume diffusion measurements in some B2 intermetallics are reviewed. Results of recent Ni self-diffusion measurement carried out by tracer technique in nearly equiatomic NiTi compound at 1285 K in the pressure range of 0-0.91 GPa are presented. Our investigations proved that the volume diffusion coefficient is independent of the external pressure, the evaluated effective activation volume is close to zero. Results may refer either to interstitial diffusion mechanism or vacancy mediated diffusion, indicating that in the latter case the vacancy concentration is pressure independent in the investigated pressure range. Results of calculations carried out in the framework of the Ren-Otsuka model on the pressure dependence of the defect concentrations in NiAl are given.