Localized deformation at initial stages of plastic flow in high-manganese steel

Abstract

The work is devoted to the study of macroscopic localization of plastic deformation during uniaxial tension of single crystals of the Hadfield steel (Fe – 13 % Mn – 1.03 % C). In the course of studies at the stage of easy sliding, significant differences were found in the nature of macrolocalization of plastic deformation in the single-crystal samples under study. All patterns of deformation localization observed in these cases can be divided into two types. The first type of strain localization corresponds to the initiation at the upper yield point and further propagation of the strain front, which gradually transfers the sample material from undeformed state to deformed one. This manifested itself most clearly in single crystals oriented along the tension axis [377] and [355], where the strain localization pattern appears as a single zone of localized deformation on the yield plateau. Such a deformation front passes through the sample volume only once as a Chernov-Luders band. In this case, the flow of the material is carried out without hardening until all its elements are transferred to the deformed state. Single zones of strain localization were also observed at the stages of easy sliding and yield plateau in the Hadfield steel single crystals oriented along the tension axis [123] and [012]. In the second type of localization, at the stage of easy sliding, synchronous movement along the pattern of several deformation centers occurs. Their movement can be unidirectional and counter, and the speeds are both the same and different from each other. Further deformation of the Hadfield steel single crystals oriented along the tension axis [355] or [012], led to the movement of two deformation localization centers at the stages of easy sliding. In single crystals oriented along [111], the strain localization pattern is respectively represented as four localized strain sites. Consequently, the synchronous movement of deformation fronts occurs along an already deformed, albeit to a small extent, material. As a reason for the difference between the two types of macrostrain localization at stage I (the easy sliding stage and the yield plateau), the number of active sliding systems or tensile twinning in the studied single crystals can be discussed based on crystallographic analysis and metallographic studies.