Just another WordPress site - Ruhr-Universität Bochum

Abstract

The mechanical properties of materials are determined by the nature of the in- teratomic bonds in the system and the material's microstructure. Concerning the latter, it is known that e.g. in ultra ne grained materials, coatings, or lamellar alloys, interfaces play the decisive role. In this talk ways to characterize the cohesive, elastic, and plastic properties of homophase interfaces, i.e. grain boundaries, shall be presented. The rst part will focus on the in uence of segregated impurities on the structure and cohesion of special grain boundaries in transition metals. The results demonstrate that ab-initio electronic structure methods are necessary to derive the correct trends. But at the same time these can then be explained by a simple physical model, which allows for generalization and extrapolation. In the second part, the elastic and plastic properties of special grain boundaries in aluminium are investigated. A scaling scheme to bridge the length scales between ab-initio results and the input parameters of continuum methods will be presented and discussed. Another aim of an ongoing ICAMS project is the developement of a relationship between the grain boundary degrees of freedom, like the Miller indizes of the grain boundary plane or the misorientation angle, and the characteristic elastic and plastic quantities as elastic constants, sliding energy barriers, the theoretical tensile strength, and the work of separation. The strategy and rst results will be introduced.