Model studies on the dynamics of grain boundaries in metals
Guest Speaker： Prof. Dmitri A. Molodov，RWTH Aachen University, Germany
Inviter: lecturer Bingbing Zhao
Date&Time: Monday, 15. July，14：00-15：30
Venue: Yiucheng Lecture Hall（500） , Xu Zuyao Building
Biography:
Prof. Molodov studied physical metallurgy and metal physics at the University of Steel and Alloys in Moscow, Russia. He completed his doctorate in 1985 under the supervision of Prof. Shvindlerman at the Institute of Solid State Physics of the Russian Academy of Sciences. In the early 1990s, he moved to Aachen, Germany, first as a scientist and later as an Alexander von Humboldt Fellow. Since 1995, he has led the group "Grain Boundary Dynamics" and became a professor in 2006 at the Institute of Physical Metallurgy and Metal Physics, RWTH Aachen University. Since 2016, he has also been a visiting professor (distinguished professor from 2021) at the International Research Organization for Advanced Science and Technology (IROAST) at Kumamoto University, Japan.
Prof. Molodov is an internationally renowned expert in physical metallurgy, recognized for his expertise in investigations of dynamic properties of grain boundaries in crystalline materials utilizing unique experimental techniques and computer modelling. He is the author and co-author of more than 210 publications in international journals and has made over 80 contributions to academic conferences. He is also the editor of two books: “Recrystallization and Grain Growth”, Springer, 2001, and “Microstructural Design of Advanced Engineering Materials”, Wiley-VCH, 2013.
Abstract:
The research on grain boundary dynamics in metals will be reviewed. Modern techniques for the investigation of grain boundary motion in bicrystals - on-line measurements based on X-ray diffraction, in-situ observation utilizing the orientation dependence of secondary electrons in a SEM or the anisotropy of the reflectivity of visible light - will be presented.
The boundary dynamics is strongly dependent on the grain boundary character, which is commonly reduced to the orientation relationship between adjacent grains and the inclination of the boundary plane. The misorientation dependence of the motion of specific capillary driven grain boundaries, the faceting and migration behavior of low angle grain boundaries, as well as various grain boundaries with misorientations close to the Σ3 CSL orientation relationship in high-purity Al bicrystals will be considered and discussed in terms of the inclination dependence of grain boundary energy.
The results of measurements of the stress induced boundary motion associated with shear deformation of the crystal region swept by the boundary, performed on bicrystals with various structurally different grain boundaries, will be reported. The analysis of the solutions of the Frank-Bilby equation for the dislocation content of symmetric tilt grain boundaries for a number of grain and twin boundaries will be presented. The extended geometric model of grain boundary migration - shear coupling to evaluate the coupling factor (amount of shear) for twin and grain boundaries in various crystal structures based on this analysis will be introduced.