Effect of Void on Yielding Behaviors in a Bicrystalline Copper
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JMEPEG https://doi.org/10.1007/s11665-020-05159-0
Effect of Void on Yielding Behaviors in a Bicrystalline Copper Lin Yuan, Chuanlong Xu, Jie Xu, Debin Shan, and Bin Guo (Submitted July 24, 2020; in revised form August 27, 2020; Accepted: 20 September 2020) Nanovoids make a big contribution to the plasticity and failure of nanocrystalline metallic materials. To develop a further understanding of the role played by spherical voids in governing the plasticity of nanocrystalline metals, molecular dynamics simulations are performed on bicrystalline copper models with a spherical void at room temperature under 1 3 108 s21 strain rate. The simulation results indicate that the introduction of void lead to the reduction in yield stress with increasing void diameter. The spherical void acts as either a barrier or a source for dislocations. For intergranular spherical void, the dislocations are emitted from the intersections between the void and grain boundary (GB). However, the initial dislocation nucleation site transits from GBs to spherical void surface at a critical diameter of 9.5 nm in the models with intragranular void. According to the Lubarda model, the dislocation emission critical stress at intermediate void diameters is effectively predicted, but it is not applicable for the model with extremely large and small void since the factors of GB and grain orientation are not considered. Some more suitable models need to be developed. Keywords
bicrystalline copper, grain boundaries, molecular dynamics, nanovoid, plasticity
1. Introduction The plasticity of metallic materials is closely related to inherent defects within these materials. Dislocations, voids and GBs are the most basic and abundant ones. Voids are popular defects in metallic materials, some of which are distributed at GBs (intergranular voids) and others in grain interior (intragranular voids). Voids are considered to be the main cause of damage and failure of ductile metallic materials. There usually exist numerous nanovoids in the metallic materials fabricated in laboratories. The dynamic evolution of such nanovoids in the interior of metallic materials during plastic deformation is hard to be captured by the available experimental methods. In contrast, such dynamic evolution of internal defects during plastic deformation can be readily obtained by MD simulations. It will be of great significance to do researches in terms of the dynamic evolution of nanovoids and their contributions to plasticity during the plastic deformation of metallic materials by MD simulations. However, voids do not contribute solely to materials plasticity but with the company of other defects, e.g., dislocations and GBs. The interactions among dislocations, Lin Yuan, Chuanlong Xu, Debin Shan, and Bin Guo, National Key Laboratory for Precision Hot Processing of Metals, Harbin 150001, China; and School of Materials Science and Engineering, Harbin Institute of Technology, No. 92 West Dazhi Street, Nan Gang District, Harbin 150001, China; Jie Xu, School of Materials Science and Engi
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