DIFFUSION OF TITANIUM AND NIOBIUM IN BCC TI-NB ALLOYS

The diffusion coefficients for titanium and niobium radioactive tracers were simultaneously measured in Ti, Ti94.6Nb5.4, Ti80.4Nb19.6, and Ti64.3Nb35.7 over the temperature range from 950°C to 1511°C using standard lathe-sectioning techniques. The samples were initially heat treated by annealing above the phase-transition temperature and then either cooling slowly to room-temperature or quenching. The room-temperature crystal morphology was then examined using x-ray diffraction. Alloy concentrations were chosen both to suppress the transition and to obtain the metastable phase. The data may be described by Ti: DTi=4.54×10-4e-31 300RT cm2/sec; DNb=2.91×10-4e-31 030RT cm2/sec; Ti94.6Nb5.4: DTi=1.27×10-3 e-35 610RT cm2/sec; DNb=1.79×10-3e-38 220RT cm2sec; Ti80.4Nb19.6: DTi=3.15×10-3 e-41 960RT cm2/sec; DNb=1.18×10-2e-47 330RT cm2/sec; Ti64.3Nb35.7: DTi=2.51×10-1 e-59 020RT cm2/sec; DNb=2.98×10-1e-61 730RT cm2/sec. The hypothesized enhancement of diffusion by -phase fluctuations or effects of the hcp to bcc phase transformation cannot be ruled out by this work, but are certainly not supported directly by the present results. © 1979 The American Physical Society.