EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Only minute additions of certain elements can render a material either ductile or brittle. This phenomenon is known for a long time. Already in 1803, it was shown that small additions of Bi, Sn, and Pb turn ductile Au into a brittle material and in 1888, Sir Roberts-Austen conducted a comprehensive series of experiments that showed how the potency of an alloying element to embrittle Au is related to its atomic size without any knowledge of the origins for this behaviour. Because these effects not only take place in Au, understanding the underlying phenomena is of vital importance for modern materials design.
The present work focusses on the same system and applies state-of-the-art methods for materials design to reveal the underlying phenomena. First principles based calculations of the segregation energy and embrittlement potencies are conducted for a large number of alloying elements at a grain boundary in Au. The results agree well with the experimental observations. In combination with semi-empirical models, the reasons for the experimentally observed relation of atomic size of the alloying elements with the embrittlement potency is uncovered.