Relaxation Mechanisms, Structure and Properties of Semi-Coherent Interfaces

Shuai Shao,Jian Wang

doi:10.3390/met5041887

Abstract

In this work, using the Cu–Ni (111) semi-coherent interface as a model system, we combine atomistic simulations and defect theory to reveal the relaxation mechanisms, structure, and properties of semi-coherent interfaces. By calculating the generalized stacking fault energy (GSFE) profile of the interface, two stable structures and a high-energy structure are located. During the relaxation, the regions that possess the stable structures expand and develop into coherent regions; the regions with high-energy structure shrink into the intersection of misfit dislocations (nodes). This process reduces the interface excess potential energy but increases the core energy of the misfit dislocations and nodes. The core width is dependent on the GSFE of the interface. The high-energy structure relaxes by relative rotation and dilatation between the crystals. The relative rotation is responsible for the spiral pattern at nodes. The relative dilatation is responsible for the creation of free volume at nodes, which facilitates the nodes’ structural transformation. Several node structures have been observed and analyzed. The various structures have significant impact on the plastic deformation in terms of lattice dislocation nucleation, as well as the point defect formation energies.

Highlights

The semi-coherent interface has very high mechanical and thermal stability, and is widely occurring in a broad range of materials, such as epitaxial layers, precipitation materials, and both diffusional and diffusionless phase transformations [1]
We studied the energy minimization mechanism of semi-coherent interfaces by performing atomistic simulations and dislocation theory analysis on a Cu–Ni (111) semi-coherent interface as a model system
By examining the generalized stacking fault energy (GSFE) profile of the coherent Cu–Ni interface, two stable structures (FCC and ISF, which correspond to the energy minima on the GSFE curves) and a high-energy structure are identified

Summary

Introduction

The semi-coherent interface has very high mechanical and thermal stability, and is widely occurring in a broad range of materials, such as epitaxial layers, precipitation materials, and both diffusional and diffusionless phase transformations [1]. The core-size of the misfit dislocation in the interfaces with lower shear resistance (such as the FCC {111} interfaces) tends to spread, thereby reducing the strain concentration associated with the dislocation core necessary for the nucleation [20,21,22,32]. In this scenario, the dislocation intersections (nodes) may be the only source available for lattice dislocation nucleation. We have correlated the variation of the aforementioned properties to the structural variations of the nodes

Atomistic Modeling Method and Details

Structures and Properties at Nodes

Discussion and Conclusions