Self-diffusivities of Ti and Cr were determined in (TixWyCrz)B2 ceramics, which were a model system for the development of in situ reinforced boride ceramics by tailored precipitate formation. Homogeneous solid solutions with the compositions, (Ti0.3W0.5Cr0.2)B2, (Ti0.5W0.3Cr0.2)B2 and (Ti0.4W0.5Cr0.1)B2, were studied at 1100 to 1500C by using ion-implanted stable 49Ti and 54Cr isotopes and secondary ion mass spectrometry. The diffusivities of each element obeyed an Arrhenius law. The Cr diffusivities of all 3 compounds could be fitted to an unique Arrhenius plot:

D (m2/s) = 2 x 10-7 exp[-3.5(eV)/kT]

The Ti diffusivities were smaller, by 1 to 2 orders of magnitude, than the Cr diffusivities: with the higher activation enthalpy of 3.9eV and approximately the same pre-exponential factor.

Self-Diffusion of Transition Metals in (Ti,W,Cr)B2 Solid Solutions. H.Schmidt, G.Borchardt, C.Schmalzried, R.Telle, H.Baumann, S.Weber, H.Scherrer: Journal of Materials Science, 2006, 41[13], 4233-7