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Microstructure Evaluation for Time Dependent Nucleation Protocols in KJMA Kinetics

Published online by Cambridge University Press:  15 February 2011

Eloi Pineda  and
Daniel Crespo
Eloi Pineda
Affiliation:
E.U. d'Enginyeria Tècnica Agrícola (ESAB), Universitat Politècnica de Catalunya.Urgell 187, 08036-Barcelona, SPAIN Departament de Física Aplicada, Universitat Politècnica de Catalunya, Campus Nord UPC, Mòdul B4, 08034 - Barcelona, SPAIN, crespo@fa.upc.es.
Daniel Crespo
Affiliation:
Departament de Física Aplicada, Universitat Politècnica de Catalunya, Campus Nord UPC, Mòdul B4, 08034 - Barcelona, SPAIN, crespo@fa.upc.es.
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Abstract

The microstructure developed in a first order phase transformation is obtained using a populational extension of the Kolmogorov, Johnson-Mehl and Avrami (KJMA) model, PKJMA. PKJMA allows one to determine the grain size distribution resulting from nucleation and growth kinetics. PKJMA is grounded on the mean field hypothesis that the free space around the growing grains is randomly distributed, independent of the grain radius. Although this approach is perfectly valid for the case of constant nucleation, a detailed analysis of the model shows that this hypothesis does not hold in the case of time dependent nucleation protocols or pre-existing nuclei. In this work, the PKJMA model has been improved by estimating the average free surface around the grains as a function of their radius and the time elapsed since nucleation. The resulting model gives quantitative determination of the microstructure developed under a variety of nucleation and growth processes: pre-existing nuclei, constant nucleation, and the combination of both mechanisms, constant and radius dependent growth rates. Comparison with Monte Carlo simulations, showing a quantitative agreement will be presented.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 580: Symposium E – Nucleation & Growth Processes in Materials , 1999 , 321
Copyright
Copyright © Materials Research Society 2000

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