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Measurements and Modeling of Precipitation and Dissolution

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Measurements and Modeling of Precipitation and Dissolution during Cooling and Preheating of Extrusion Billets

Børge Holme, SINTEF, Oslo, Norway
Sylvain Gouttebroze, SINTEF, Oslo, Norway
Calin Marioara, SINTEF, Trondheim, Norway
Bjørn Rune Henriksen, Elkem Aluminum, Kristiansand, Norway
Kristina Lewin, Sapa Technology, Finspång, Sweden

Track: BILLET PROCESS and EQUIPMENT - Casting Homogenization

ABSTRACT --- A semi-empirical mathematical model has been developed for
the quantitative prediction of the amount and sizes of Mg+Si-containing
precipitates in 6xxx alloy billets during the cooling process after homogenization
(soaking) and during the preheating prior to extrusion. The model is based on
nucleation criteria, diffusion of solute in the aluminum matrix, and phase
diagram descriptions. Moreover, this model is coupled with the ALSTRUCmodel,
which gives the required microstructure information from the DC-casting
and homogenization processes. Laboratory heat treatment experiments on
AA6063, including interrupted quenching of a series of samples from high
temperature, have been carried out. The samples from the experiments have been
extensively characterized using FEG-SEM, TEM, and EPMA for the purpose of
tuning and verifying the model predictions. Examples of calculations are shown
to shed light on the microstructure evolution during billet cooling.

© Extrusion Technology for Aluminum Profiles Foundation (ET Foundation). All rights reserved. No part of The Proceedings may be reproduced in any form without the express written permission of the ET Foundation.