Strain hardening behavior of polycrystalline iron and low-carbon steels—A statistical analysis

Abstract

Descriptions of strain hardening are reviewed and a common basis is sought to correlate variations of plastic behavior with microstructure. Both the reported occurrence of two-stage hardening and the magnitude of the associated change of Hollomon strain hardening exponent are shown to be closely related to carbon content and grain size. Values of the Hollomon strain hardening parameters are also shown to be correlated with carbon content and grain size together. It is demonstrated that this “double-n” behavior is not characterized by reduced strain hardening rate when the strain is greater than ~0.1, as has been suggested, but by rapid hardening at low strain. These observations are collated into a consistent account of the dependence of plastic behavior on carbon content and grain size. It is inferred that the strain hardening exponent for stage 1 is governed by both of these microstructural factors although the sensitivity to carbon content is not readily discernible in the data analyzed, apparently because grain size is strongly dependent on carbon content and their separate effects are normally obscured.