<p>A framework is described using the phase-field crystal model for the study of premelting in binary alloys through short-range interfacial interactions that arise from the structure of grain boundaries. A nonconserved model A formulation of PFC was used to model grain boundaries in two dimensions for several different angles of misorientation: 27.8, 21.8, 17.8, 13.2, and 5 degrees. The character of the premelting transition, whereby a liquid-like film develops at a defect at temperatures below the melting point, changed with misorientation angle. An excess mass over the grain boundary can be defined as an analog to the liquid layer thickness due to premelting. It is found that low-angle grain boundaries remain at a relatively constant value of excess mass, and indeed can remain solid above the melting point. High-angle grain boundaries have a logarithmically increasing width that diverges at the melting point. A width-dependent energy can be defined called the disjoining potential that takes into account structure, interfacial and bulk energies to describe the liquid-layer width. The form of this disjoinging potential was found to be exponential and monotonically decreased as width increased for high angles and produced an attractive minimum for low angles. The results of this work were compared to a pure material from a previous study.</p> / Master of Applied Science (MASc)

<p>Premelting is the formation of a thin, thermodynamically stable, liquid-like film at an interface for temperatures below the equilibrium melting temperature. Using a Monte Carlo technique, the underlying short range structural forces for premelting at the grain boundary can be directly calculated. This technique is applied to a (i) Σ9 ⟨115⟩ 120^o twist boundary and a (ii) Σ9 ⟨011⟩ {411} symmetric tilt boundary in an embedded atom model of Aluminum-Magnesium alloy. Both grain boundaries exhibit disordered structures near the melting point that depend on the concentration of Magnesium. The behavior is described quantitatively with sharp interface thermodynamics, involving an interfacial free energy that depends on width of the grain boundary, referred to as the disjoining potential. The disjoining potential calculated for boundary (i) displays a decreasing exponential dependence on width of the grain boundary, while the disjoining potential of (ii) features a weak attractive minimum. This work is discussed in relation to a previous study using pure Nickel, results of which can be useful to the theoretical study of thermodynamic forces underlying grain boundary premelting in an alloy.</p> / Master of Science (MSc)