Atomic-scale study of compositional and structural evolution of early-stage grain boundary precipitation in Al–Cu alloys through phase-field crystal simulation

Abstract

Interfacial solute clustering is an essential step preceding grain boundary (GB) precipitation. Both states, i.e., clusters and precipitates, alter the mechanical, chemical, and corrosion properties of materials. Continuum models cannot capture the atomic details of these phenomena, specifically of the transition from clustering to precipitation. We thus use the structural phase-field crystal (XPFC) model to study the compositional and structural evolution during GB clustering in Al-Cu alloys. The results show that the compositional evolution is dominated by solute segregation to lattice defects at the very beginning and then by confined spinodal decomposition along the GBs. The latter leads to a steep increase in the concentration and then the formation of disordered clusters. This structure acts as a precursor for phase nucleation, just like the decomposed solid solution, and Guinier-Preston zones are the precursors of the thermodynamically stable Al 2 Cu phase in the interior of grains. Two modes of spinodal decomposition are found. (a) On low-angle tilt GBs, spinodal decomposition occurs at the dislocations that constitute the GB. (b) On high-angle tilt GBs, spinodal decomposition takes place inside the entire GB plane. In either case, the structural transition from the disordered low-dimensional precursor states to an ordered phase state takes place following the compositional enrichment. These results shed light on atomic-scale early-stage GB decomposition and precipitation processes in Al-Cu alloys and enrich our knowledge about the coupling effects between compositional and structural evolution during GB phase transformation phenomena.

Molecular-Level Insights into the Nucleation Mechanism of One-Component Soft Matter Icosahedral Quasicrystal Studied by Phase-Field Crystal Simulations

“…The truncated correlation function, Ĉ 2 , as shown in Figure a, is related to a pair potential with two length scales determined by the positions of the peaks of Ĉ 2 . Such a two-length-scale pair potential can give rise to a thermodynamically stable ordered structure including periodic crystals and QCs in the framework of both the CDFT and the PFC methodology. , In recent years, the PFC model has been successfully utilized to study the nucleation and growth of a variety of structures at the particle level. − By substituting eqs and into eq , we obtain the free energy functional of the structural PFC model …”

Atomic-Scale Investigation of the Pattern Formation of Quasicrystal Growth by Phase-Field Crystal Simulations

“…The positions of the two peaks k 1 and k 2 in truncated correlation function Ĉ 2 correspond respectively to the two characteristic length scales d 1 and d 2 in real space . Such a two-length-scale pair potential can stabilize the ordered structures including periodic crystals and QCs in the framework of both the CDFT and the PFC methodologies. , Recently, the PFC model has been successfully utilized to study the atomic-scale mechanisms for the nucleation and growth of solid phases with different lattice structures on the atomic scale. ,,,− Here, the free energy functional of the structural PFC model reads where the scaled particle number density field represents the local deviation from a uniform reference liquid with density ρ 0 . The correlation function is the summation of two Gaussian peaks, where , σ is the effective temperature, σ Mi is related to the height of peak i , and frequency wave vectors k i and α i are the position and width of the Gaussian peaks, respectively.…”

Perspective: New directions in dynamical density functional theory

“…Recent studies of PFC models have focused on active matter with [212][213][214] and without [215][216][217][218][219][220][221] inertia, amorphous solids [222], bifurcation diagrams [219,220,[223][224][225], colored noise [226], cubic terms [227], crystals [228], dislocation lines [229], electromigration [230], grain boundaries [231,232], mixtures [200,220,[233][234][235], nucleation [236], solidification [237,238], and stress tensors [239].…”