A mathematical model to predict the through-thickness microstructure and texture
changes during hot tandem rolling has been developed for two commercially significant
aluminum alloys - AA5182 and AA5052. The model includes a plasticity component to
model the temperature and deformation during rolling as well as an interpass component to
model the microstructure, texture and temperature changes which occur in the strip between
the rolling passes.
The plasticity model was developed using a commercial finite element package
DEFORM - a 2-D transient Lagrangian model which couples the thermal and deformation
phenomena which occur during strip rolling and is able to predict the temperature, strain rate
and strain distribution in the strip at any position in the roll bite.
The interstand model includes semi-empirical equations describing the microstructure
(percent recrystallization and recrystallized grain size) and texture changes occurring in the
strip between the rolling passes. The interstand model also includes a temperature module to
predict the through-thickness temperature distribution in the strip based on the one-dimensional
heat conduction equation which is solved by a finite difference method.
The semi-empirical equations used in the interstand model were developed using
experimental data for the two alloys. The experimental programme was carried out at Alcan
International's Banbury and Kingston Laboratories, as well as at the Atomic Energy of
Canada Limited Chalk River Laboratories. The experimental programme involved plane
strain compression testing industrial rolled samples of AA5182 and AA5052 aluminum
alloys based on a test matrix which covered similar temperature, strain and strain rate
conditions as those seen in industrial hot tandem rolling. The samples were given a single
deformation and then quenched immediately to preserve the as-deformed structure. The
samples were then heat-treated in a salt bath for various lengths of time and the percent
recrystallization, recrystallized grain size and texture changes during recrystallization were
measured. A temperature compensated time parameter was used to convert the isothermal
recrystallization and texture kinetics to non-isothermal applications.
Validation of the model using industrial data and samples indicated that it gave
reasonable predictions for the temperature, grain size and volume fraction of some of the
deformation texture components after recrystallization was completed. However, the model
tended to over-estimate the mill loads in the last stands for both the AA5182 and AA5052
alloys and tended to underestimate the amount of cube and S texture in the recrystallized
strip.
A sensitivity analysis of the process parameters indicated that both the microstructure
and texture were most sensitive to the rolling temperature. Indicating the need for good
control of temperature during rolling operations as well as accurate temperature predictions
for process modelling activities. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/6242 |
| Date | 05 1900 |
| Creators | Wells, Mary A. |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Format | 9174241 bytes, application/pdf |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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