Computational simulation of grain boundary segregation of solute atoms in nanocrystalline metals

Abstract

The remarkably high strength of nanocrystalline metals is of great interest to researchers and seems to open up many interesting design applications. However, a particularly vexing problem is the low ductility and microstructural instability of nanocrystalline metals that decreases their strength over time. In addition, there is a bottleneck of critical grain size in the fine-grain strengthening effect of nanocrystalline metals. How to stabilize the microstructure of nanocrystalline metals and how to obtain the ultimate strength of nanocrystalline metals and maintain some plasticity through grain refinement are hot topics in the frontier of materials science. Previous experimental works have well demonstrated that grain boundary (GB) segregation of solute atoms can effectively overcome the intrinsic disadvantages of nanocrystalline metals. However, the microscopic mechanisms are not well understood yet, which hinders the further optimization of the comprehensive mechanical properties of nanocrystalline metals through the concept of GB segregation engineering. With the rapid development of computational materials science in the past two decades, many studies have been carried out on the relationship between solute atoms and GB properties, and fruitful results have been achieved. In this paper, the latest advances in computational simulation of GB segregation of solute atoms in nanocrystalline metals are reviewed, including the effects of solute atoms on GB structure and energy, mechanical properties of the segregated GBs, and the microscopic deformation mechanism of the segregated GBs.