Initiation of discontinuous precipitation at interphase boundaries in a two-phase Zn-6.3 at.% Ag alloy

W. Xu*, Y. P. Feng, Y. Li

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

Discontinuous precipitation (DP) was found to initiate at both η′-η′ interphase and η′-η′ grain boundaries in a two-phase Zn-6.3at.% Ag alloy consisting of ε and supersaturated η′ phases. The η′-ε interphase boundaries at which DP has initiated illustrated a sinusoidal interface during ageing, which implies that the morphological instability is a prerequisite for the DP initiation at an η′-ε interphase boundary. The application of the morphological instability model for solid-solid interfaces has indicated that the interface protuberances grow into the supersaturated η′ and the interphase boundary becomes unstable since the observed wavelength of serrated η′-ε interphase boundaries was larger than the critical value predicted by the model. A solute-depleted region is therefore established in front of the η′-ε interphase boundary, which provides an appropriate site leading to a DP reaction. Based on this, a nucleation mechanism of DP at the interphase boundaries is proposed accordingly: the allotriomorphs of DP can be directly developed from ε protuberances of a serrated interphase boundary.

Original languageEnglish
Pages (from-to)1773-1787
Number of pages15
JournalPhilosophical Magazine
Volume84
Issue number17
DOIs
Publication statusPublished - 11 Jun 2004
Externally publishedYes

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