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Directionality and Column Arrangement Principles of Precipitates in Al-Mg-Si-(Cu) and Al-Mg-Cu Linked to Line Defect in Al

Abstract

In the structures of all metastable precipitates in Al-Mg-Cu and Al-Mg-Si alloys, we find that column surrounding of an element column in the needle/lath direction order according to simple principles. Advanced transmission electron microscopy and DFT calculations support the principles originate with a line defect, which is a segment of a <100>Al column shifted to interstitial positions. We propose the defect aids solute decomposition by partitioning the FCC matrix locally into columns of fewer and higher number of nearest neighbours, which suit smaller and larger size solute atoms, respectively. The defect explains how <100> directionality of the precipitates can arise in a cluster. Ordering of a few defects leads naturally to GPB zones in Al-Mg-Cu and to β'' in Al-Mg-Si.

Category

Academic chapter/article/Conference paper

Client

  • Research Council of Norway (RCN) / 197405
  • Research Council of Norway (RCN) / 193619
  • Sigma2 / NN9158K

Language

English

Author(s)

Affiliation

  • SINTEF Industry / Materials and Nanotechnology
  • SINTEF Industry / Metal Production and Processing
  • Norwegian University of Science and Technology
  • Norsk Hydro ASA

Year

2017

Publisher

Trans Tech Publications

Book

The 15th International Conference on Aluminium Alloys

Issue

877

ISBN

978-3-0357-1050-2

Page(s)

461 - 470

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