Microstructure based modeling for the mechanical behavior of ferrite-pearlite steels suitable to capture isotropic and kinematic hardening

This study proposes a new microstructure based model for the mechanical behavior of non-microalloyed ferrite-pearlite steels. Its main originality consists in estimating the internal stresses evolving with strain. It takes into account two contributions corresponding to two different scales of the microstructure: the huge internal stresses generated in pearlite all along the deformation and the mesoscopic strain incompatibility between ferrite and pearlite. This estimation allows the distinction to be made between the isotropic and kinematical components of work-hardening. The parameters of the model have been adjusted on numerous results from the literature concerning fully ferritic or pearlitic steels. The performance of the model is then demonstrated on datasets from the literature concerning steels with different fractions of pearlite. The predictions of the model are excellent concerning both tensile behavior and Bauschinger effects. The size effects of lamellar pearlite have been reviewed in this paper, i.e., the impact of interlamellar spacing on mechanical properties. In pearlite, the yield strength scales with s(-1), the internal stress with s(-1/2) and the macroscopic strain-hardening (i.e., slope of the tensile curve) do not depend on interlamellar spacing. This review gives new perspectives for the understanding of the mechanical behavior of lamellar structures, such as pearlite or bainite. (C) 2008 Elsevier B.V. All rights reserved.