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

Alloying elements segregate to interfaces and reduce their migration rates due to solute drag. Semi-quantitative solute drag models proposed by Cahn, Lücke and Stüwe have been applied successfully to interpret experimental observations of grain boundary migration in the presence of solutes. This allows to extract empirical solute drag parameters such as solute segregation energy and trans-interface diffusivity. Advances in atomistic scale computational techniques particularly Density Functional Theory (DFT) offer an alternative to assess the segregation energy at interfacial sites and solute diffusion across the interface.

The aim of this work is to propose a rigorous approach to incorporate atomistic details of the solute-interface interactions into a solute drag model to predict grain boundary migration rates. The proposed approach is validated with experimental migration data of a 30˚<111> grain boundary in Au containing Fe and Bi impurities. DFT simulations to quantify the segregation energy at various grain boundary sites indicate a strong attraction of Bi and a weak attraction of Fe to the grain boundary. As a result, Bi impurities (2 ppm) are found to have a stronger retarding effect than Fe (20 ppm). To evaluate the solute diffusivity across the grain boundary, several solute-vacancy pairs at the grain boundary are considered and activation barriers for diffusion are determined by DFT simulations using the Nudged Elastic Band method. Finally, the proposed methodology is integrated with the phase field method to describe the experimental grain boundary migration rates during recrystallization. The challenges and future work will be discussed related to the proposed approach to develop a predictive simulation tool for grain growth and recrystallization in metals and alloys.