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Stabilization and Strengthening of Nano-Crystalline Immiscible Alloys

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George Mason University Fairfax United States

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Nano-crystalline immiscible metallic alloys are very promising structural materials combining high mechanical strength with extraordinary structural stability at high temperatures. The goal of the proposed research is to develop a fundamental understanding of the physical mechanisms responsible the thermal stability and strength of immiscible alloys focusing on the Cu-Ta system as a specific model. To achieve this goal, new computer simulation approaches will be developed for prediction and optimization of thermal and mechanical properties of immiscible alloys. Using a wide range of advanced atomistic simulation methods, a systematic study of thermodynamic properties and kinetic characteristics of grain boundaries GBs in Cu-Ta alloys will be conducted. This will include calculations of key properties of GBs as the GB free energy, GB diffusivity, GB mobility and GB resistance to deformation and sliding. These simulations will be performed on both polycrystalline samples, representing collective behavior of multiple GBs, and on individual crystallographically characterized boundaries in order to establish a link between GB structure, GB crystallography, and thermodynamic and kinetic factors of thermal stability. This work will provide the fundamental knowledge needed for optimization of synthesis and processing routes of Cu-Ta alloys and for discovery of new high-strength immiscible alloy systems in the future. The proposed research is synergistic with experimental work on immiscible structural alloys currently underway at the Army Research Laboratory.

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Technical Report,15 Feb 2015,14 Feb 2018



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Approved For Public Release;

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