Atomistic study and continuum modeling of solute strengthening in slip-CTB interaction

Abstract

The slip-coherent twin boundary (CTB) interaction, which is one of the most important issues determining the strength and ductility of the face-centered cubic metals, is investigated by molecular dynamics (MD) simulations on a bi-crystal model of Ni with interstitial Cr and Fe in CTB. Two interaction types, i.e., absorption and transmission, are observed, with prominent dependence on both the type and fraction of the solute. The threshold shear stress triggering the slip-CTB reaction event is quantitatively evaluated, and based on the local lattice friction, a new interpretation of the mechanism for solute affected slip-CTB interaction is proposed. A continuum model for solution affected slip-CTB interaction is established from a discrete dislocation scenario, including modified formulations in terms of the balanced condition of stress acting on the leading partial and elevated lattice friction, where the solute effect is effectively accounted and incorporated. Accordingly, the criterion to determine the nature of slip-CTB reaction is proposed, yielding good prediction of the critical events observed in MD simulations. This paper provides critical understanding and predictive tools for solute affected slip-CTB interaction in Ni, and offers new insights into alloy and microstructure engineering of Ni based superalloys with improved mechanical properties.