LAUSR

Abstract Pinning effect of second-phase particles has been demonstrated as an extremely effective way to impede grain boundary (GB) migration to increase strength or thermal stability, particularly for nano-scale materials. Previous studies on the particle pinning mainly focus on the incoherent particle; the coherent particle pinning, more effective in retarding the GB migration, has not yet been completely understood, owing to varied phase boundary (PB) energy essentially and additionally considered. In this paper, the maximum and the average pinning forces of the coherent particle are modeled, considering the evolved GB shape. A critical criterion is deduced to judge the condition that the pinning force from multiple particle can be obtained by a linear summation of the pinning force from the individual particle. Using Cu–Ag as the model system, molecular dynamics (MD) simulations are performed to study the interaction between the coherent Ag particles and the planar Cu GBs, where the maximum and the average pinning forces are estimated as functions of particle parameters (e.g. the size, the volume fraction, the shape and the orientation of particle). By combination of models and MD simulations, the pinning effect of coherent particles is attributed to a change in Gibbs free energy ascribed to the GB energy and the PB energy, while the maximum and the average pinning forces are enhanced with an increase in volume fraction or a decrease in size of particle.