Computing Grain Boundary Diagrams of Thermodynamic and Mechanical Properties

TL;DR

This paper demonstrates a method to compute grain boundary diagrams of thermodynamic and mechanical properties in alloys, using simulations validated by microscopy, to explore structure-property relationships at the grain boundary level.

Contribution

It introduces a novel approach to generate temperature- and composition-dependent grain boundary diagrams for thermodynamic, structural, and mechanical properties using hybrid MC/MD simulations.

Findings

Validated simulated GB structures with electron microscopy.

Computed GB diagrams for multiple properties including strength and toughness.

Proposed a new research direction for GB property analysis.

Abstract

Computing the grain boundary (GB) counterparts to bulk phase diagrams represents an emerging research direction. Using a classical embrittlement model system Ga-doped Al alloy, this study demonstrates the feasibility of computing temperature- and composition-dependent GB diagrams to represent not only equilibrium thermodynamic and structural characters, but also mechanical properties. Specifically, hybrid Monte Carlo and molecular dynamics (MC/MD) simulations are used to obtain the equilibrium GB structure as a function of temperature and composition. Simulated GB structures are validated by aberration-corrected scanning transmission electron microscopy. Subsequently, MD tensile tests are performed on the simulated equilibrium GB structures. GB diagrams are computed for not only GB adsorption and structural disorder, but also interfacial structural and chemical widths, MD ultimate tensile strength, and MD tensile toughness. This study suggests a research direction to investigate GB composition-structure-property relationships via computing GB diagrams of thermodynamic, structural, and mechanical (or potentially other) properties.