Solute-atom segregation to 〈110〉 symmetric tilt grain boundaries

Abstract

Segregation of substitutional, oversized solute atoms to both equilibrium and metastable structures of twenty-one 〈110〉 symmetric tilt grain boundaries (GBs) in an f.c.c. binary alloy is investigated with atomistic simulations. The Monte Carlo technique is employed to determine the interfacial excess and the solute distribution in GB structures for a bulk solute concentration of 4 at.%. Results from these simulations are used to demonstrate the shortcomings of simple geometric GB parameters for predicting variations in the interfacial excess from GB to GB. The interfacial excess is also found to vary from one structure to another for the same GB. An example of a segregation-induced congruent GB phase transition is also presented. Accurate segregation free energies for individual sites in GBs are calculated with the overlapping distributions Monte Carlo technique. Segregation entropies are determined and are found to be a linear function of the segregation internal energies for the same GB sites.