Aging precipitation kinetics of Mg-Sc alloy with bcc+hcp two-phase

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Abstract

In our previous research, we reported that Mg-Sc alloys with a bcc (β) phase showed significant age hardening by the formation of fine hcp (α) precipitates in the β phase. In this study, we investigated the kinetics of the aging precipitation in the α+β two-phase Mg-Sc alloy. The incubation time for age hardening became shorter with increasing aging temperature. The relationship between the volume fraction of α precipitates and aging time was better described by the Austin-Rickett equation than by the Johnson-Mehl-Avrami-Kolmogorov equation, and the obtained n values are 1.2–1.4. According to the n values and the morphology of fine α precipitates, the mechanism of α precipitation in the Mg-Sc alloy with an α+β two-phase was proposed to be a diffusion-controlled reaction, including the one-dimensional growth of α precipitates at a constant or decreasing nucleation rate. In addition, the activation energy for α precipitation was calculated to be 83.5 kJ mol−1. This value is much smaller than that of self-diffusion in Mg, while it is almost the same as that of grain boundary diffusion in Mg, namely interface diffusion. This reveals that the growth of α precipitates is dominated by interface diffusion along the boundaries between the α precipitate and the β phase.

Original languageEnglish
Pages (from-to)854-860
Number of pages7
JournalJournal of Alloys and Compounds
Volume747
DOIs
Publication statusPublished - 2018 May 30

Keywords

  • Age hardening
  • Magnesium alloy
  • Phase transformation

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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