Metastable phase formation during the decomposition of Fe-20 at.% Mo

D. Isheim*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

The early stages of the isothermal decomposition of an Fe-20 at.% Mo alloy at 500°C have been studied by means of atom-probe (AP) and field-ion microscopy (FIM), as well as high-resolution (HREM) and conventional (CTEM) transmission electron microscopy. CTEM reveals a characteristics modulated structure oriented along the (100)-type directions of the b.c.c. matrix. Electron diffraction patterns show satellite-like intensities close to the fundamental reflections in 〈100〉-type directions, indicating an approximate 6 nm characteristic length scale of the decomposition microstructure. FIM and HREM reveal precipitates about 2 nm in size with a b.c.c. structure formed coherently within the matrix. AP analyses show these precipitates to consist of almost pure Mo. The size misfit between the Mo-rich precipitates and the Fe-rich matrix causes large coherency strains, resulting in precipitate alignment along 〈100〉-type directions. The Mo-rich b.c.c. solid solution precipitates in a metastable equilibrium with the Fe-rich b.c.c. matrix, whereas the formation of the equilibrium intermetallic phases is kinetically suppressed. A coherent metastable miscibility gap between the Fe-rich and the Mo-rich b.c.c. solid solution is assessed by incorporating a continuum elasticity strain-energy term into the Gibbs free energy.

Original languageEnglish (US)
Pages (from-to)2873-2883
Number of pages11
JournalActa Materialia
Volume48
Issue number11
DOIs
StatePublished - Jun 30 2000

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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