Segregation and embrittlement of gold grain boundaries

Grain boundary (GB) segregation of solutes can significantly alter material properties, the effects of which have first been observed more than two hundred years ago. After an introduction that shortly summarizes the historic development of the study of segregation, this work conducts an investigation on the segregation tendencies of 27 alloying elements to an Au GB and a surface with first principles calculations, semi-empirical modelling, and a phenomenological model of segregation. The effect of alloying elements on GB cohesion are evaluated and both detrimental (Bi, Cl, As, K) and beneficial elements (Al and the 3d transition metals) for alloying are identified. By comparing to experimental results from over two centuries, the used methodology and the obtained results are validated. The main origin of the GB cohesion effect can be revealed, i.e. the size mismatch between alloying elements and Au.