Defect substructure energy landscape in polycrystalline Al under large deformation: insights from molecular dynamics

NJ Chen and SY Hu and W Setyawan and PV Sushko and SN Mathaudhu, JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 22, 3340-3351 (2023).

DOI: 10.1016/j.jmrt.2022.12.131

Tens-nanometer sized defect substructures such as dislocation network, nanotwin and new grain or phase may form during solid phase processing (SPP), which affect the energy landscape, hence, the stability and evolution of phase and structure. Developing non -equilibrium thermodynamic models needs the correlation among the energy, defect sub- structure and deformation. In the current work, we use molecular dynamics (MD) method to simulate defect substructure evolutions in polycrystalline Al under compress and shear stresses. The effect of local stresses on the formation and transformation of typical defect substructures were analyzed. It was found that transitions from FCC, nanotwin, HCP, BCC, HCP to FCC lead to the formation of subgrains facilitated with large grain rotation. Our results demonstrate that point defect concentrations (e.g., HCP, dislocation core atoms) can be used as internal variables to describe defect substructures, such as dislocations, nanotwins and sub-grain boundaries. An energy landscape of defect substructures in polycrystalline Al under compress and shear stresses was established which shows un-stable and metastable defect substructures. Approaches to developing more accurate en-ergy landscapes for understanding and predicting microstructure evolution under SPP was discussed.(c) 2023 Battelle Memorial Institute. Published by Elsevier B.V. on behalf of Brazilian Metallurgical, Materials and Mining Association. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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