Dilute alloys which contained up to 0.56wt%Ta were prepared. Diffusion couples between these alloys, and pure Fe, were prepared by spot-welding. After vacuum annealing, the diffusion profiles were determined by using electron probe microanalysis. The diffusion parameters were determined at one standard deviation by using the Grube method. The diffusion rate of Ta in austenite was about 6 times higher than that for the self-diffusion of Fe. In ferrite, the diffusion of Ta required a higher activation energy than did other transition metals. The diffusivity of Ta in austenite (0.54%Ta alloy), at between 1147 and 1347C, was described by:

D (mm2/s) = 6.72 x 103 exp[-319000/RT]

The diffusivity of Ta in ferrite (0.54%Ta alloy), at between 826 and 894C, was described by:

D (mm2/s) = 2.75 x 106 exp[-324000/RT]

Q.A.Shaikh: Materials Science and Technology, 1990, 6[12], 1177-80