Deformation Behavior of Iron Single Crystals under Simple Shear

Abstract

Measurements were made on the plastic deformation of iron single crystals subjected to the simple shear on the slip systems of {110} <111> and {112} <111> at various temperatures.
The results obtained are summarized as follows: (1) The characteristics of three-tages hardening were observed in the stress-train curves tested at 300°K and 195°K with shear on the plane (112). The work hardening rates in the stage I and II were increased and the strains in the two stages were decreased as the shearing direction were deviated from the direction [111]. (2) The temperature dependence of the yield stresses in the shear deformation was markedly different from that in the tensile tests, the former being smaller. This suggests that the normal stress component is an important factor in controlling the mechanism of deformation. Moreover, in the shear deformations for {112} <111> and {110} <111> slip systems, the variations of the yield stress with temperature were remarkably different. (3) In the shear tests at 77°K, where the shearing plane was (101) or (112), the serration associated with deformation twinning was observed in the stress-strain curves in the work-hardening region. It was also shown that the resolved shear stress required to produce twinning varied with the shearing direction and plane. Both the slip and twin bands were observed on the surface of specimens sheared at 77°K. (4) The fine structure in the cleavage surfaces depends largely on the deformation modes; in the tensile tests, cleavage surface is composed of many blocks divided by [110] and [110] directions; similar blocks, however, were not observed in the sheared specimens.