Discontinuous precipitation in an austenitic Fe-Mn-V-C alloy has been studied using transmission electron microscopy of extraction replicas and thin foils. The vanadium carbide precipitates formed during the discontinuous reaction are present either as particles or as long fibres. The coincidence site lattice model for high-angle grain boundaries has been used to relate each precipitate morphology to the nature of the grain boundary at which it forms. Fibrous precipitation occurs behind those boundaries in which there is a comparatively high density of coincidence sites, whereas particulate precipitation occurs at low coincidence boundaries.
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