Zhen Yue's research works | Wuhan University of Technology and other places

The deformation and failure process of B4C under [001] quasi-isentropic compression. a The stress–strain relationship. b The average angle of three-atom chains and intra-icosahedra change with strain. c The structure at ε = 0.091, remains relatively unchanged in the elastic deformation. d The structure at ε = 0.175, where the von Mises stress reaches its maximum. e The structure at ε = 0.180, where icosahedra sliding occurs. f The structure at ε = 0.185, where parallel amorphous bands occur. g The structure at ε = 0.350 is completely damaged

The local structural evolution of B4C under [001] quasi-isentropic compression. a The structure at 0.010 strain before the significant structural changes. b The structure at 0.110 strain, where new B–B bonds between chains and adjacent icosahedra form. c The calculated isosurfaces (at 0.90) of the ELF. d The structure at 0.161 strain where the B5–B6 bond breaks. e The structure at 0.175 strain where the stress reaches the maximum value. f The structure at 0.180 strain where the deconstruction of icosahedra propagates. Magenta balls represent the C1, C2, and B7 atoms in a chain, while blue balls denote selected B1–B6, and B8 atoms in the distinct icosahedra

EOS for B4C under [001] quasi-isentropic compression. a Pressure–volume data from our simulations, Murnaghan EOS fitting, and other simulated and experimental data. b Temperature–pressure relationship, compared with the results of previous studies

The deformation and failure of B4C under [010] quasi-isentropic compression. a The stress–strain relationships. b The average angle of three-atom chains and intra-icosahedra change with strain. c The structure at ε = 0.210, where local shear amorphous bands are parallel along two orientations

The local structural evolution of B4C under [010] quasi-isentropic compression. a The structure at 0.010 strain before the structural change. b The structure at 0.110 strain where the new chains–icosahedra bonds form. c The structure at 0.204 strain where the B5–B6 bond breaks. d The structure at 0.207 where the B5 atom is dragged out of the icosahedron

Atomistic explanation of compression-induced deformation mechanisms in boron carbide

February 2024

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Applied Physics A

The compression-induced deformation mechanisms of boron carbide (B4C) have not been well understood due to its complex crystal structure. Here, we investigate the mechanical behaviors and deformation mechanisms of B4C under various compression conditions, using molecular dynamics simulations with a machine-learning force field. Two structural transitions in B4C under bulk compression are identified: the formation of new chains–icosahedra bonds, and icosahedral deconstruction. The former triggers the “pop-in” event observed in the nanoindentation experiments due to chain bending, while the latter facilitates icosahedral sliding and amorphization. Furthermore, the results reveal a mechanism involving an intermediate structure characterized by the development of new chains–icosahedra bonds across the entire model, followed by the amorphization process. This mechanism induced by increased stress in icosahedra due to the new chains–icosahedra bond formation plays an important role in significantly improving the strength and ductility of B4C. In contrast, B4C with free surfaces or nanopores exhibits a direct transformation from chain bending to icosahedral deconstruction without the intermediate structure formation, consequently reducing strength and ductility. However, this intermediate configuration is not stable and maintained only under stress, because structural recovery within non-amorphized regions occurs after amorphization under quasi-static compression with a relaxed stress state. This study provides a thorough understanding of the deformation behaviors and mechanisms of B4C.

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Zhen Yue’s research while affiliated with Wuhan University of Technology and other places

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