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.
Highlights
In polycrystalline materials, grain boundaries (GBs) are the ubiquitous crystal imperfection that can often control materials fabrication processing and performance[1,2,3,4,5,6]
This study aims at using a classical GB embrittlement (GBE) and Liquid metal embrittlement (LME) system, Al–Ga (Ga-doped Al), as a model system to establish an exemplar to investigate GB composition–structure–property relationships via computing GB diagrams of thermodynamic, structural, and mechanical properties
We adopted isobaric semi-grand canonical (constant N(Δμ)PT) ensemble hybrid Monte Carlo and molecular dynamics (MC/MD) simulations to obtain equilibrium GB structures in Ga-doped Al using an embedded-atom model (EAM) potential originally developed by the Srolovitz group[44]
Summary
Grain boundaries (GBs) are the ubiquitous crystal imperfection that can often control materials fabrication processing and performance[1,2,3,4,5,6]. It was proposed to develop the GB counterparts to bulk phase diagrams as a generally useful materials science tool[11]. GB diagrams have only been developed to represent a limited number of thermodynamic and structural properties, mostly notably adsorption (i.e., the GB excess of solutes)[18,21,22,23,24] and interfacial structural disorder[11,14,15,16,17,21,22,23,24]. This work strives for further constructing GB diagrams to represent other useful equilibrium structural characters (e.g., GB structural and chemical widths) and computed mechanical properties
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