Strengthening Mechanisms and Features of Strain Stages in High-Manganese Austenitic Hadfield Steel

Abstract

The paper presents the study of the deformation effect on high-manganese austenitic Hadfield steel. The dependences of the flow stress and the strain-hardening coefficient on the degree of plastic deformation in uniaxial tension revealed that the linear stage II of strain-hardening at ε ~ 5% can be divided into two substages different in the type of dislocation substructures and values of strain-hardening coefficients. The change in the strain-hardening coefficient correlates with the time when the twinning processes are switched on and the beginning of the transition of the dislocation substructure from one type to another. The following quantitative parameters were determined: the volume fraction of the material caught up by slip and twinning; the volume fractions of the material where twinning develops in one, two, and three systems. Twinning develops most intensively in the range of ε = 5–20%. The involvement of various types of defects (microtwins and dislocations) in the process of deformation does not depend on the method of plastic deformation (tension, rolling). The role of crystallographic texture, which manifests itself in an increase in the Schmid factor during the formation of microtwins, is determined, since microtwinning entails orientational softening and facilitates the sliding process. The presence of minimal and even zero values of the Schmid fa-ctor during twinning was revealed in individual grains. In these grains, the driving force of twinning is the internal stress fields, the occurrence of which is due to the incompatibility of the deformation of neighboring grains.