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Temporal Evolution of Bimodal Distribution of γ’ Precipitates in Ni-Al-Mo Alloys under the Influence of Coherency Strains

Published online by Cambridge University Press:  21 February 2011

A.D. Sequeira ,
H.A. Calderon  and
G. Kostorz
A.D. Sequeira
Affiliation:
now: Institute for Advanced Materials JRC, P.O. Box 2, 1755ZG Petten, The Netherlands. on leave from Departamento de Física - ITN, Estrada Nacional 10, P-2685 Sacavém, Portugal.
H.A. Calderon
Affiliation:
now: Dep. Ing. Metalurgica ESIQIE - IPN, Apdo. Postal 75–874, Mexico D.F. 07300.
G. Kostorz
Affiliation:
Institut für Angewandte Physik, ETH Zürich, CH-8093 Zürich, Switzerland
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Abstract

The influence of coherency strains produced by the γ-γ’ lattice mismatch, δ, on the decomposition process of Ni-Al-Mo alloys with a bimodal size distribution is presented. Samples with δ ranging from positive to negative, were investigated in a double-step aging procedure. The evolution of the microstructure and the kinetics of coarsening were studied using transmission electron microscopy (TEM). The lattice mismatch between the matrix and the different classes of precipitates was determined by high-resolution high-temperature x-ray diffraction. It is shown that the strain fields produced by the lattice mismatch can influence dramatically the decomposition of metallic alloys. It is suggested that the reduction of the coarsening rate of the large precipitates, the fast coarsening rate of the small precipitates and the distortions detected in the matrix are all direct consequences of the elastic fields produced by the γ-γ’ lattice mismatch.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 398: Symposium C – Thermodynamics and Kinetics of Phase Transformations , 1995 , 483
Copyright
Copyright © Materials Research Society 1998

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References

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