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MICROSTRUCTURAL MODELLING OF INDUSTRIAL THERMOMECHANICAL PROCESSING OF ALUMINIUM ALLOYS

Objective

The overall objectives of this project are to develop micromechanical models for the kinetics and the microstructural changes that take place during and after each deformation step in industrial hot processing of aluminium alloys.
Micromechanical models have been developed for the kinetics and the microstructural changes that take place during and after each deformation step in industrial hot processing of aluminium alloys. The effect of the microstructural changes in between deformation passes was expressed in terms of changes in the constitutive equations for flow stress as a function of strain, strain rate and temperature so that they could be incorporated directly into finite element codes which model the overall mechanical and thermal conditions of the working process. The research was carried out on 3 generic alloys. 4 deformation modes were selected: industrial hot rolling, hot plane strain compression (PSC), hot extrusion and hot torsion. It was found that PSC cold simulate well the hot rolling process. Subgrain size and misorientation between neighbouring subgrains were characterized and reproducible results obtained. The microstructures developed after deformation by PSC, torsion, rolling and extrusion were compared. The microstructural and textural development during PSC was studied. After recrystallization, the microstructural and textural development was assessed. The nucleation mechanism of cube oriented grains were studied. The results were used in a new model developed to describe the recrystallization microstructures and textures. Reasonable, qualitative agreement between experiment and model predictions were obtained. 2 codes, the Risoe and the Los Alamos polycrystal plasticity code, were used to simulate the experimental deformation texture development. Semiquantitative agreement was obtained. The effects of alloying elements and deformation condition on the formation of deformation cones at large intermetallic particles were modelled. It was shown that there is a clear transition from low to high deformation temperature behaviour and excellent agreement between experimental and modelled results was obtained. A Eulerian finite element model of the roll bite during hot flat rolling was used to predict the local temperature, strain and strain rate as a function of position. Exploitation of the project results should result in improved production practices at hot mills. Already the results have been used to limit the cost of industrial trials aimed at reducing the dispersion of anisotropy in 3104 canstock. One of the goals is to apply the knowledge to reducing the gauge of canstock, thereby keeping the aluminium beverage can competitive.
The effect of the microstructural changes in between deformation passes will be expressed in terms of change in the constitutive equations for flow stress as a function of strain, strain rate and temperature so that they can be incorporated directly into finite element codes which model the overall mechanical and thermal conditions of the working process. Several other major deliverables will be developed, e.g. reproducibility of data for industrial processing using laboratory scale equipment, exactness of the use of total equivalent plastic strain for both flow stress and microstructural evolution, and role of texture development in determining recovery and recrystalisation kinetics.

Coordinator

Riso National Laboratory
Address
Frederiksborgvej 399
4000 Roskilde
Denmark

Participants (4)

Hydro Aluminium AS
Norway
Address

6601 Sunndalsora
Pechiney
France
Address
10 Place Des Vosges
92048 Paris La Défense
Sintef - Foundation for Scient. & Indust. Research at the Norvegian Inst. of Technology
Norway
Address

7034 Trondheim
UNIVERSITY OF MANCHESTER INSTITUTE OF SCIENCE AND TECHNOLOGY
United Kingdom
Address
Sackville Street
88 Manchester