A microstructure-based constitutive model for pearlite

Abstract

Fully pearlitic eutectoid steels have an excellent compromise of mechanical strength and ductility and are widely used for rails, prestressing tendons and high- strength wires. These excellent mechanical properties are a consequence of their particular nanocomposite structure combining thin cementite lamellae (~12% volume fraction) with ferritic lamellae. This complex substructure entails a complex microstructural and property evolution with applied strain that is difficult to model. In this work, a microstructure-based constitutive model for pearlite accounting for both the elastoplastic behaviour and the damage evolution is presented. The original formulation, valid for mesoscopic scales, considers the behaviour of ferrite and cementite separately, assuming that strengthening occurs through the mechanisms acting in ferrite. For its application in macro-scale systems such as wire drawing, a multi-colony homogenization strategy has been applied. For damage, a Continuum Damage Mechanics approach adapted to the features of pearlite has been adopted with the coupling of damage to the mechanical response. The model has been implemented for use in finite element simulations and has been calibrated using experimental data of tensile and torsion tests. Subsequently, the model has been validated, confirming its predictive capabilities across various aspects, including the mechanical response under different stress states, the build-up of internal stresses and the evolution of the microstructure with deformation.