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Precipitation Kinetics in Metastable Solid Solutions – Theoretical Considerations and Application to Cu-Ti Alloys

Published online by Cambridge University Press:  26 February 2011

R. Kampmann ,
H. Eckerlebe  and
R. Wagner
R. Kampmann
Affiliation:
GKSS-Forschungzentrum, Institut für Physik D-2054 Geesthacht, FR Germany
H. Eckerlebe
Affiliation:
GKSS-Forschungzentrum, Institut für Physik D-2054 Geesthacht, FR Germany
R. Wagner
Affiliation:
GKSS-Forschungzentrum, Institut für Physik D-2054 Geesthacht, FR Germany
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Abstract

Cu-2.9 at.% Ti single crystals were homogenized at various temperatures (780 °C ≤ TH ≤ 960°C) and quenched. Subsequent isothermal aging at 350 °C led to phase separation, the kinetics of which have been followed by employing small-angle neutron scattering (SANS). According to comple-mentary transmission electron and analytical field ion microscopy studies, the resulting transformation products of this first order phase transition are stoichiometrically ordered ellipsoidal Cu4Ti particles, the aspect ratio of which changes with aging time (t) as revealed by two-dimensional SANS-detection. In the early stages of phase separation, the decomposition kinet-ics are strongly influenced by the quenching rate via quenched-in excess vacancies. During aging the structure factor S(K,t) develops a maximum, the height (Sm) of which increases and the position (Km) of which decreases with t. Neither Sm(t) nor Km(t) follow a power law as predicted by several recent theories on spinodal decomposition. On the other hand, the time evolution of the mean Ti-rich cluster size (R), their number density (Nv), and the supersaturation (Δc) as inferred from the SANS-data and the diffuse Laue-scattering, are well predicted by a precipitation model which describes nucleation, growth and coarsening as competing processes.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 57: Symposium I – Phase Transitions in Condensed Systems--Experiments and Theory , 1985 , 525
Copyright
Copyright © Materials Research Society 1987

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References

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