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

D. Isheim

doi:10.1016/S1359-6454(00)00097-5

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

D. Isheim^*

^*Corresponding author for this work

MRC - Materials Research Center

Research output: Contribution to journal › Article › peer-review

24 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 language	English (US)
Pages (from-to)	2873-2883
Number of pages	11
Journal	Acta Materialia
Volume	48
Issue number	11
DOIs	https://doi.org/10.1016/S1359-6454(00)00097-5
State	Published - Jun 30 2000

Funding

The author would like to acknowledge the motivation for this work and the support by his advisor, the late Professor Peter Haasen. He would also like to thank C. Borchers, R. Busch, F. Gärtner, A. Pundt, Professor R. Kirchheim, and Professor R. Wagner for helpful discussions; F. Appel for his assistance with the Philips CM30 at the GKSS-Forschungszentrum Geesthacht, Germany, and Professor K. Samwer for the provision of the piston-and-anvil quencher of the Lehrstuhl f. Physik I, Universität Augsburg, Germany. The friendly encouragement of Professor D. N. Seidman is appreciated. This manuscript was prepared at Northwestern University and the author was supported by the National Science Foundation, Division of Materials Research (Dr B. MacDonald, grant officer), grant DMR-9728986, by the Deutsche Forschungsgemeinschaft, and the Alexander von Humboldt Foundation through the Max Planck Research Prize of DNS.

ASJC Scopus subject areas

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

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10.1016/S1359-6454(00)00097-5

Cite this

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title = "Metastable phase formation during the decomposition of Fe-20 at.% Mo",

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.",

author = "D. Isheim",

note = "Funding Information: The author would like to acknowledge the motivation for this work and the support by his advisor, the late Professor Peter Haasen. He would also like to thank C. Borchers, R. Busch, F. G{\"a}rtner, A. Pundt, Professor R. Kirchheim, and Professor R. Wagner for helpful discussions; F. Appel for his assistance with the Philips CM30 at the GKSS-Forschungszentrum Geesthacht, Germany, and Professor K. Samwer for the provision of the piston-and-anvil quencher of the Lehrstuhl f. Physik I, Universit{\"a}t Augsburg, Germany. The friendly encouragement of Professor D. N. Seidman is appreciated. This manuscript was prepared at Northwestern University and the author was supported by the National Science Foundation, Division of Materials Research (Dr B. MacDonald, grant officer), grant DMR-9728986, by the Deutsche Forschungsgemeinschaft, and the Alexander von Humboldt Foundation through the Max Planck Research Prize of DNS. ",

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doi = "10.1016/S1359-6454(00)00097-5",

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PY - 2000/6/30

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N2 - 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.

AB - 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.

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ER -

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

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