  The carbon atom distribution in a tempered martensitic steel processed by
cold drawing was investigated with a three-dimensional atom probe. Data clearly
show that cementite starts to decompose at the early stage of deformation. This
indicates that the driving force of cementite decomposition during plastic
deformation is not related to a strong increase of the interfacial energy.
Carbon atmospheres were also analysed. They probably result from pipe diffusion
of carbon atoms along dislocations pined by Fe3C carbides.
