Exploring Grain Boundary Energy Landscapes With the Activation-relaxation Technique
Kathleen Alexander, Massachusetts Institute of Technology
Grain boundaries (GBs) are microstructural defects in virtually all metallic and ceramic materials and often are the source of failure in engineering applications. However, there are types of GBs that are resistant to the failure mechanisms that grain boundaries are generally prone to. The field of grain boundary engineering (GBE) has demonstrated that it is possible to significantly improve macroscopic materials performance (such as corrosion and cracking resistance) by altering the fraction, distribution, and connectivity of GBs of certain types in a given specimen. However, the advancement of GBE has long been stunted by an incomplete understanding of how to predict the properties of individual GBs. The main barriers to the development of predictive GB structure-property relationships include the complexity of the GB space (GBs occupy a vast, five-dimensional space) and deficiencies in existing computational approaches that investigate GB kinetic properties on time scales that are many orders of magnitude shorter than the experiments they are intended to simulate.
We present a new approach to simulating GB kinetic behavior that is intended to combat these challenges by making use of the activation-relaxation technique (ART), a method for efficiently mapping energy landscapes. GB energy landscapes can be used in combination with kinetic Monte Carlo for the computational study of GB properties under experimentally relevant conditions, thus creating a GB simulation tool for which there are virtually no inherent limitations on the loading state, temperature, and processing times considered. As a first step in this project, an implementation of ART has been developed for the study of GB energy landscapes. The energy landscapes of several specific grain boundaries have been mapped out. Initial studies of how GB structure maps to GB energy landscapes and how GB energy landscapes are affected by an externally applied pressure have been performed.
Abstract Author(s): Kathleen C. Alexander