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)

IS-J 9660 SI.pdf (139 kB)
Supplemental Material

Available for download on Sunday, May 12, 2019

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