The solute diffusion of iron in the light rare-earth metals cerium, praseodymium and neodymium

Abstract

The thin layer sectioning technique has been used in order to determine the solute diffusivity of 59Fe tracers in the light rare-earth metals cerium, praseodymium and neodymium. The measurements were made both in the close-packed (f.c.c. for Ce and double-h.c.p. for Pr and Nd) and in the high-temperature b.c.c. phases of the solvent metals. The diffusivities of iron are extremely high, with values exceeding 10 −5 cm 2/sec at temperatures above 0.7 T m ( T m melting temperature of the solvent metal). The activation energies are much lower than the activation energy for self-diffusion, of the order of 10 kcal/mole. The results indicate that iron is a fastdiffusing solute, its diffusion in the rare-earth metals taking place probably by means of the dissociative mechanism, with a predominantly interstitial component. Several simultaneous measurements of the diffusivity of 54Mn suggest that Mn is also a fast-diffusing solute, though to a lesser extent than 59Fe.