Editors: | F. Kongoli, S. Kobe, M. Calin, J.-M. Dubois, T. Turna |
Publisher: | Flogen Star OUTREACH |
Publication Year: | 2018 |
Pages: | 154 pages |
ISBN: | 978-1-987820-90-4 |
ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
Grain boundary migration is an important phenomenon during hot working of materials. It is key to understanding the microstructural evolution during the deformation process, and is an essential mechanism for microstructural design of materials. This phenomenon of grain boundary migration during hot forming has been a central research area in material science in the last century. It was long assumed that grain boundary migration during cold deformation does not occur. The generation of ultrafine grained and nanocrystalline material by low temperature heavy plastic deformation has been introduced during the last two decades. In order to understand the minimum grain size, which can be achieved by these processes, it becomes quite evident that grain boundary migration plays a key role. A central question of this grain boundary movement is: "What are the driving forces and what controls the resistance against the movement of the grain boundaries at these low temperatures?" Further important points resulting from this question are: "What is the role of thermally activated processes and what is the contribution of stress and strain induced transfer of atoms from one grain to the other?" This presentation will focus on these central questions by analyzing grain boundary movement as a function of deformation temperature, strain rates, strain paths, impurities, and alloying elements. It will be shown that grain boundary movement during heavy plastic deformation at low temperature has a similar importance as in the case of dynamic recrystallization during hot working, only the driving forces are different. Finally, it will be shown that these phenomena of deformation induced grain boundary migration at low temperatures are important in order to understand the strength of ultrafine grained and nanocrystalline materials.