Effect of Spatial Correlation of Particles on Ostwald Ripening
The study of phase transitions is of interest to scientists concerned with states of aggregation as well as to metallurgists and physicists. The precipitation or phase separation in solids is one of the interesting and useful fields of study for metallurgists and materialists. The precipit in process in alloys generally consists of the initial nucleation and growth, and the late coarsening which is the growth of a larger precipitate particle at the expence of smaller one. The coarsening process of particles, or Ostwald ripening process was theoretically studied by Lifshitz and Slyozov1 and Wagner2 (LSW). Their theory is applicable only for the system of infinitesimal volume fraction of precipitates. The modification of the LSW theory has been made by Ardell3 and many other workers4,5,6 to take into account the effect of volume fraction. Recently theoretical treatments of coarsening process have been made from the view point of the dynamics of phase transition 7,8,9. While the t1/3 law predicted by the LSW theory is found to hold, the observed size distributions of precipitate particles are frequently different from the one predicted by the theory of LSW or Ardell. We examined the size distribution of particles in Cu-Co and Al-Li alloys and pointed out the importance of the effect of volume fraction on the coarsening 10,11. As Ostwald ripening is the competitive growth of particles controlled by diffusion of solute atoms, the growth rate of particles is to be influenced by the surrounding particles through the diffusion field.
KeywordsFurnace Cobalt Shrinkage
Unable to display preview. Download preview PDF.
- 2.C. Wagner, Theorie der Alterung von Niederschlagen durch Umlosen, Z. Elektrochemi., 65:581 (1961).Google Scholar
- 4.A.D. Brailsford and P. Wynblatt, The dependence of Ostwald ripening kinetics on particle volume fraction, Acta metall., 27:489 (1978).Google Scholar
- 5.C.K.L. Davies, P. Nash and R.N. Stevens, The effect of volume fraction of precipitate on Ostwald ripening, Acta metall., 28:179 (1979).Google Scholar
- 8.K. Kawasaki and Y. Enomoto, Elementary derivation of kinetic equations for Ostwald ripening, Physica, 135A:426 (1986).Google Scholar
- 10.T. Eguchi, Y. Tomokiyo, K. Oki and Y. Seno, Coarsening of cobalt precipitates in copper-cobalt alloys, in: “Phase Trasformation in Solids”, T. Tsakalakos, ed, North-Holland, Amsterdam, 1984.Google Scholar
- 11.T. Eguchi, Y. Tomokiyo and S. Matsumura, Electron microscopic observation and its interpretation of Ostwald ripening in precipitation dynamics in alloys, Phase Transitions, 8:213 (1987).Google Scholar
- 13.Y. Tomokiyo, S. Matsumura and M. Toyohara, Strain contrast of coherent precipitates in Cu-Co alloys under exitation of high order reflections, J. Electron Microscopy, 34:338 (1984).Google Scholar