The diffusion of antimony in alpha iron |
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Authors: | G A Bruggeman J A Roberts |
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Affiliation: | 1. Materials Sciences Division, Army Materials and Mechanics Research Center, 02172, Watertown, Mass. 2. Department of Materials Science and Engineering, University of California, 94720, Berkeley, Calif.
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Abstract: | Diffusion coefficients of antimony in α-iron were determined in the temperature range 700 to 900°C using the residual activity method. Specimens were large-grained polycrystals for the higher temperature measurements and single crystals for the low temperature measurements. Above 800°C the data may be represented by the equationD sb(cm2/s) = (440 ± 200) exp - (270,000 ± 7000)/RT]. The activation energy (reported in J/mole) is approximately equal to that measured for iron self-diffusion in this same temperature range, although the antimony diffusion coefficients are a factor of ten larger than the iron self diffusion coefficients. The potential for strongly coupled vacancy-antimony motions is demonstrated, based on the observed enhancement of iron self diffusion in dilute iron-antimony alloys. Finally molybdenum is shown to have a negligible effect on the diffusion of antimony in α-iron. These results are discussed in relation to the phenomenon of temper brittleness in steels. Embrittlement kinetics in iron-antimony alloys are shown to be consistent with an antimony diffusion controlled segregation mechanism. |
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