Predicting mechanical properties of carbide-metal interfaces from first principles
Résumé
The cavity initiation observed in ductile, brittle and intergranular creepdamages is often explained by a fracture of interface between carbideand metallic lattices. Understanding the mechanisms of fracture allowsthe prediction of the cavity density as a function of applied strain,which law strongly affects the damage evolution. This study focuseson interfaces between a metallic matrix (Fe, Ni) and a representativecarbide M23C6 . Surface, interface and fracture energies are calcu-lated via DFT based on chemical potential analysis. Then, interfa-cial fractures stresses are estimated by the UBER (Universal BindingEnergy Relation) model and compared with good correlation to theresults of fully-DFT simulations of tensile test carried out using var-ious methodologies. We investigate the dependence of the interfacialmechanical behavior on chemical compositions, crystallographic struc-tures and magnetic orderings. The predicted fracture stresses of coher-ent interfaces range between 14 and 20 GPa. Then, the effects of someincoherent interfaces are investigated. The resulting critical stress isabout two times smaller, which is consistent with experimental obser-vations showing that interfacial fracture rather occurs at incoherentinterfaces. Finally, segregations effects are investigated.