A unified model of grain-boundary segregation kinetics

Abstract

A unified model of grain-boundary segregation kinetics is established, which can simulate the equilibrium and non-equilibrium grain-boundary segregation kinetics during isothermal ageing. The results of model fittings/predictions are in a good consistence with those of the experiments. Values of several important parameters, such as vacancy formation energy, vacancy migration energy, and complex migration energy derived by model fittings, show a reasonably good agreement with those in the references. Relationship between the equilibrium and non-equilibrium grain-boundary segregation mechanisms is discussed in detail. The segregation peak/depletion trough observed in the non-equilibrium segregation kinetics may be ascribed to the vacancy flux. The equilibrium segregation kinetics is considered as a special case in non-equilibrium segregation kinetics with the zero vacancy flux. Both the equilibrium and non-equilibrium segregation kinetics are believed to be dominated by vacancy-solute complex flux. The proposed unified model can be a significant progress in grain-boundary segregation theory, with applications in guiding the design of materials.

Cascading phase transformations in high carbon steel resulting in the formation of inverse bainite: An atomic scale investigation

“…2). Faulkner 27 and Wu 28 have reported that when an elemental spike due to the thermally induced non-equilibrium segregation occurs, a solute depletion trough is observed ahead of the prior austenite grain boundary. Thus, the cementite midrib forms from austenite with a lower Si concentration ahead of the prior austenite grain boundary and not the equilibrium Si concentration of 0.5 at.%.…”

Modelling the Spatial Evolution of Excess Vacancies and its Influence on Age Hardening Behaviors in Multicomponent Aluminium Alloys

“…Herein, the trapped vacancies can be temporarily detached from the vacancy-solute atom complexes, meanwhile, new vacancies are bound to the individual solute atoms and/or solute clusters to maintain the local thermodynamic equilibrium condition until the global equilibrium state is reached [39,40]. The probability of the trapped vacancy escaping from the trapping site is controlled by the magnitude of binding energy between the vacancy and individual solute atoms and/or solute clusters, which can influence the average vacancy diffusivity according to Eq.…”