A small-angle neutron scattering study of decomposition dynamics in Ni/sub 87. 5/Si/sub 12. 5/
The kinetic behavior of precipitation in a supersaturated Ni-12.5 at. % Si alloy single crystal has been studied by the small-angle neutron scattering (SANS) technique to supplement earlier transmission electron microscopy (TEM) and wide-angle x-ray diffraction (XRD) work. The SANS measurements performed at room temperature on quenched specimens subjected to isothermal anneals at 400, 450, 505 and 550/degree/C for various amounts of time have revealed the presence of an interference peak in the scattering function. The particle size, determined according to the Guinier approximation, is found to obey the t/sup 1/3/ coarsening law at long aging times. For short aging times below 500/degree/C, a classical ''growth'' stage characterized by a parabolic growth rate is noticed before coarsening takes effect--an observation consistent with our previous in-situ XRD work. The activation energy for solute diffusion is determined using the rate constants governing the growth of particle size and the variation of the mean interparticle distance. Results are in good agreement with the values given in the literature. Enhanced diffusion due to quenched-in excess vacancies is observed below 500/degree/C. The dynamical scaling law appears to be followed for the data obtained in the coarsening stage. A disruption of scaling occurs at the point when the particle growth changes from a parabolic rate behavior to a cubic coarsening rate. 8 refs., 5 figs., 2 tabs.
- Research Organization:
- Argonne National Lab., IL (USA)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 7173366
- Report Number(s):
- CONF-8710275-3; ON: DE88011997
- Resource Relation:
- Conference: International conference on applications and techniques of small angle scattering, Argonne, IL, USA, 26 Oct 1987; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
NICKEL BASE ALLOYS
AGING
PRECIPITATION HARDENING
SILICON ALLOYS
ACTIVATION ENERGY
ANNEALING
DIFFUSION
MONOCRYSTALS
NEUTRONS
NUCLEATION
SMALL ANGLE SCATTERING
SUPERSATURATION
ALLOYS
BARYONS
CRYSTALS
ELEMENTARY PARTICLES
ENERGY
FERMIONS
HADRONS
HARDENING
HEAT TREATMENTS
NICKEL ALLOYS
NUCLEONS
SATURATION
SCATTERING
360102* - Metals & Alloys- Structure & Phase Studies