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Density Functional Study of the β″ Phase in Al-Mg-Si Alloys

Abstract

The β″ phase is the major hardening precipitate in Al-Mg-Si alloys. It was studied by atomistic
calculations based on density functional theory (DFT), using an atomistic model where the
precipitate was embedded in an Al matrix. This allowed quantifying and visualizing the
coherency strain in the matrix and within the precipitates. The elastic strain was found to
decrease exponentially in the matrix as a function of distance from the precipitate interface. The
formation enthalpy of several different chemical compositions of β″ was calculated, and the
most stable composition was found to be Mg5Al2Si4. A study of the calculated valence charge
density and electron localization function showed that the covalency network between Si-atoms
in the precipitate structure is broken when the precipitate contains Al.

Category

Academic article

Client

  • Research Council of Norway (RCN) / NN2615K
  • Research Council of Norway (RCN) / NN9143K

Language

English

Author(s)

Affiliation

  • Norwegian University of Science and Technology
  • University of Oslo
  • SINTEF Industry / Sustainable Energy Technology

Year

2014

Published in

Metallurgical and Materials Transactions A

ISSN

1073-5623

Publisher

Springer

Volume

45

Issue

6

Page(s)

2916 - 2924

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