Grain-boundary shearing as a test for interface melting

Abstract

We examine the behaviour of the (310) symmetric tilt boundary with applied shear stress in a face-centred cubic Lennard-Jones crystal. Our purpose is to observe the mechanical properties of grain boundaries resulting from interface melting. The grain boundary is seen to exhibit significant self-diffusion at temperatures above 80% of the bulk melting point . Excess thermodynamic properties and the density of the system change dramatically in this region. However, the system is able to resist shear up to the higher temperature of . Plots of particle trajectories in the interface and estimates of the number of melted layers provide insight into an understanding of this behaviour.

Dislocation-Pairing Transitions in Hot Grain Boundaries

“…(9). For the boundaries with normals near [011] (small θ), non-premelted states are stable to values of γ GB (T M )/2γ SL significantly greater than one, based on the elastic-softening estimate of γ GB (T M ).…”

“…At high T , GB structures can be even more complex, as different metastable minima can be sampled through thermal fluctuations, and these interfaces can undergo a variety of phase transitions involving, e.g., defaceting and roughening [4,5], premelting [6], and solute-driven structural transformations [7]. This high-T behavior can have important consequences for properties relevant to materials processing, including GB mobility [5,8] and shear strength [9,10].…”

Phase-field crystal study of grain-boundary premelting

“…MD studies using LennardJones 7,8,9 and interatomic potentials for metals 10,11,12 and semiconductors such as silicon 13 have reported evidence for disordered layers at grain boundaries at different temperatures below 7,8,9,10,11,13 and above 12 the melting point. In addition, such layers have been reported to exhibit fluid-like properties in a MD study of grain-boundary shearing in a Lennard-Jones system where the shear modulus decreased sharply below the melting point 9 . The large fluctuations inherent in MD simulations, however, make it generally hard to compute precisely the thermodynamic properties of grain boundaries at high homologous temperature and to quantify the interaction between crystal-melt interfaces.…”

“…This allows us to make contact with sharp- 1,8 and diffuse-interface 1,27,28 theories of interfacial premelting. Like MD studies with truncated short-range interatomic potentials 7,8,9,10,11,12,13 , these theories neglect the effects of long-range dispersion forces considered in statistical theories of grain-boundary melting 29 and in theoretical 30 and experimental 31 studies of intergranular phases in ceramic materials. These forces are also neglected in the present phase-field crystal study that focuses on the structural component of the disjoining potential due to partial crystal ordering within premelted layers.…”

Structural disjoining potential for grain-boundary premelting and grain coalescence from molecular-dynamics simulations

“…The technique represents an extension of the numerous previous MD studies of grain-boundary premelting performed over the past three decades [21][22][23][24][25][26][27][28][29][30][31][32][33][34]. The technique for calculating disjoining potentials by MD is based on an analysis of the equilibrium distribution of the widths of premelted intergranular films, which are related to the underlying disjoining forces through the fluctuation-dissipation theorem.…”