Effects of dynamic grain boundary migration during the hot compression of high stacking fault energy metals

A simple one-dimensional model is proposed for predicting the effects of grain boundary migration (GBM) occurring during hot compression testing of polycrystalline specimens. Strain hardening, dynamic recovery, and GBM induced softening are accounted for using a modified Laasraoui–Jonas equation. Th...

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Bibliographic Details
Published in:Acta materialia 2002-06, Vol.50 (11), p.2801-2812
Main Authors: Gourdet, S., Montheillet, F.
Format: Article
Language:English
Subjects:
Applied sciences
Condensed matter: structure, mechanical and thermal properties
Deformation and plasticity (including yield, ductility, and superplasticity)
Dynamic phenomena
Exact sciences and technology
Grain boundaries
High temperature
Mechanical and acoustical properties of condensed matter
Mechanical properties of solids
Metals
Metals. Metallurgy
Microstructure
Physics
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Summary:A simple one-dimensional model is proposed for predicting the effects of grain boundary migration (GBM) occurring during hot compression testing of polycrystalline specimens. Strain hardening, dynamic recovery, and GBM induced softening are accounted for using a modified Laasraoui–Jonas equation. The movement of grain boundaries has two origins, viz. convection driven by material flow, and migration induced by the local dislocation density differences. The disappearance of grains during straining leads to changes in the local topology. Using parameters pertaining to aluminium, it is shown that the average grain thickness tends to a steady state value, while significant flow stress softening occurs, both predictions in agreement with experimental data. Moreover, the model allows the true average migration rate to be simply estimated from grain thickness evolution. Un modèle simple unidimensionnel est proposé pour prévoir les effets de la migration des joints de grains se produisant au cours de la compression à chaud d’échantillons polycristallins. L’écrouissage, la restauration dynamique et l’adoucissement dû à la migration sont pris en compte au moyen d’une relation de Laasraoui-Jonas modifiée. Le mouvement des joints de grains a deux origines, à savoir la convection liée à l’écoulement de la matière et la migration induite par les différences de densités de dislocations locales. La disparition de grains au cours de la déformation entraîne des modifications de la topologie locale. Dans le cas de l’aluminium, on montre que l’épaisseur moyenne des grains tend vers une valeur stationnaire tandis que la contrainte décroît de manière sensible, deux prévisions qui sont en accord avec les observations expérimentales. De plus, le modèle permet d’estimer simplement la vitesse de migration réelle moyenne à partir de l’évolution de l’épaisseur des grains.
ISSN:1359-6454
1873-2453
DOI:10.1016/S1359-6454(02)00098-8