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Probing defects in Al-Mg-Si alloys using muon spin relaxation

Abstract

Muon spin methods are very sensitive to nanoscale defects such as trace elements and vacancies in metals. This sensitivity is required when investigating Al-Mg-Si alloys, a complicated system in which diffusion-controlled phase transformations are responsible for the most important hardening mechanisms. We present muon spin relaxation experiments conducted on Al-Mg-Si alloys at measurement temperatures in the range 20–300 K. Varying the alloy composition and heat treatment, we find differences in muon depolarization in several temperature regimes. This reflects differences in concentration of several types of muon-trapping defects. We identify free solute atom and vacancy regimes, and confirm that the concentration of these defects decreases when an alloy is annealed at low temperature. We further attribute one regime to Mg-Si vacancy clustering, a mechanism required for precipitation hardening during aging. After storage at room temperature, muon trapping in this regime is more pronounced for a Mg-rich alloy than a Mg-Si-balanced alloy.
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Category

Academic article

Client

  • Research Council of Norway (RCN) / 193619

Language

English

Author(s)

Affiliation

  • Norwegian University of Science and Technology
  • Toyama University
  • Riken
  • CCLRC Rutherford Appleton Laboratory
  • SINTEF Industry / Materials and Nanotechnology

Year

2012

Published in

Physical Review B. Condensed Matter and Materials Physics

ISSN

1098-0121

Volume

86

Issue

10

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