Interdiffusion study of the topologically closed packed phase and the phase boundary compositions in the Fe-Mo system

摘要

Fe/Mo bulk diffusion couples are annealed at 1050-1200 degrees C to study the growth and diffusion behaviour of mu phase in the Fe-Mo system. Parabolic growth constants and integrated interdiffusion coefficients are determined in the mu phase. The activation energies for the growth of mu phase and for the integrated interdiffusion coefficients are estimated as 228 +/- 22 and 733 +/- 10 kJ/mol, respectively. The relatively high activation energy for interdiffusion in mu phase, determined at high homologous temperature of 0.8-0.9, indicates that mu phase grows by lattice diffusion. Phase boundary compositions, measured by EPMA, indicates the homogeneity range of mu phase to be similar to 3 at.% higher towards the Fe-rich side (i.e., 36 at.% Mo) as compared to the reported composition of 39-44 at.% Mo in the phase diagram.