Publication Date
2018
Department
Ames Laboratory; Physics and Astronomy
Campus Units
Physics and Astronomy, Ames Laboratory
Report Number
IS-J 9660
DOI
10.1016/j.actamat.2018.05.024
Journal Title
Acta Materialia
Abstract
A metastable -Al60Sm11 phase appears during the initial devitrification of as-quenched Al-10.2 at.% Sm glasses. The phase is nonstoichiometric in nature since Al occupation is observed on the 16f Sm lattice sites. Scanning transmission electron microscopic images reveal profound spatial correlation of Sm content on these sites, which cannot be explained by the “average crystal” description from Rietveld analysis of diffraction data. Thermodynamically favorable configurations, established by Monte Carlo (MC) simulations based on a cluster-expansion model, also give qualitatively different correlation functions from experimental observations. On the other hand, molecular dynamics simulations of the growth of -Al60Sm11 in undercooled liquid show that when the diffusion range of Sm is limited to ∼ 4 Å, the correlation function of the as-grown crystal structure agrees well with that of the scanning transmission electronic microscopy (STEM) images. Our results show that kinetic effects, especially the limited diffusivity of Sm atoms plays the fundamental role in determining the nonstoichiometric site occupancies of the -Al60Sm11 phase during the crystallization process.
Language
en
Department of Energy Subject Categories
36 MATERIALS SCIENCE
Publisher
Iowa State University Digital Repository, Ames IA (United States)
Supplemental Material
