On a delayed dislocation emission from hot hardness indentations

The change of the dislocation arrangements around microindentations after indentation test has been investigated by TEM and etching. The indentations were generated on {100} ‐ surfaces of iron single crystals at temperatures between 800 K and 1000 K. The change of the dislocation structure was found to depend strongly on stress and dislocation density in the deformation field. The deformation field especially acts as a dislocation source operating over long periods. The results suggest that the propagation of emitted dislocations is controlled by dragging of Cottrell‐atmospheres of carbon atoms. Conclusions regarding the hardness‐temperature relation in pure iron are drawn.