Dislocation Distribution and Work-Hardening in Iron Single Crystals Extended in the [100] and the [110] Axes

Abstract

Iron single crystals with the [100] and [110] axes were extended at 23°C and −78°C and examined by transmission electron microscopy using thin foils cut parallel to lattice planes. In the initial state of deformation, screw dislocations and edge type loops were observed predominantly. Two-dimensional tangles of dislocations approximately parallel to the slip plane were observed in the further state of deformation in the both crystals deformed at 23°C and in the [110] crystals deformed at −78°C. The relations between the flow stress τ and dislocation density ρ were analysed by the equation τ=τ₀+αGb\sqrtρ. The value of α in the crystals which had uniform distribution of dislocations was larger than that in the crystals which had non-uniform distribution. These results suggest that the work-hardening at low temperature deformation is due mainly to forest dislocations.