Work Hardening Behavior and Dislocation Structures of Iron Single Crystals during Simple Shear Tests

Stress-strain curves for iron single crystals deformed by a shearing method varied significantly with the shearing plane and direction. When the shearing plane was the (112) plane, three-stage hardening occurred at 300 and 195 K. On the other hand, for crystals sheared on the (101) plane, stress-strain curves showed the parabolic type. However, the dislocation structures were similar for crystals sheared both on the (112) and (101) planes. The distribution of dislocation in deformed crystals was inhomogeneous ; the cell structure having cell walls approximately parallel to 〈111〉 developed. The three-stage hardening behavior for crystals sheared on the (112) plane depended markedly on shearing direction. The work hardening of stage II increased as the shearing direction diverged from the slip direction [11\bar1]. This change for hardening rate in stage II with shearing direction was closely related with the stress component ratio of secondary to primary slip systems. In the crystals sheared at 77 K, where the stress-strain curves showed the parabolic type for both (101) and (112) shearing planes, the dislocation arrangement was uniform and screw dislocation was predominant.