A micromechanical constitutive modeling of WC hardmetals using finite-element and uniform field models

For constitutive modeling of WC hardmetals we used a full field finite element simulations of accurately reproduced scanning electron microscope images and a simple uniform field two-phase model. Both models combine isotropic Drucker-Prager elastic-plastic behavior of WC grains and isotropic von Mises elastic-plastic behavior of the binder, and include non-linear hardening. We performed simulations for representative volume elements using the generalized 2.5D formulation and demonstrated a good agreement between the two models in terms of the effective mechanical behavior. Effective elastic properties and coefficients of thermal expansion were obtained. Effective yield stresses evaluated at 0.1% of effective plastic strain were also computed for six different loading paths. Probability and joint probability histograms obtained in FE simulations are presented. We also studied the effect of residual thermal stresses, which appear in WC hardmetals due to cooling from sintering temperatures. Finally, we obtained a realistic yield surface for a three-dimensional microstructure using a uniform field model with spherical inclusions. This surface combines a Drucker-Prager region for moderate pressures and a von Mises region for high pressures, with a sharp transition between these two regions. Four different WC hardmetal grades were considered. In total, nine microstructures were reproduced in finite element models with the binder content ranging from 10% to 19%. A sensitivity study on the binder plastic properties was carried out, thus the obtained results for the yield surface are applicable to real hardmetals with different binder materials and various binder content.