Grain-size effects of TiC on mechanical properties in diamond/TiC combinations: A molecular dynamics exploration

JH Zhou and WJ Chen and XS Shi and CY Lu and HX Li and WJ Zheng and YH Ma and ZL Gao and JG Yang and YM He, DIAMOND AND RELATED MATERIALS, 136, 110051 (2023).

DOI: 10.1016/j.diamond.2023.110051

Epitaxial growth of titanium carbide (TiC) layer is vital for single- crystalline diamond (SCD) to ensure wettability when brazed with metals, however, how TiC grain size affects the mechanical behavior of SCD/TiC interfaces remains unclear. Herein, molecular dynamics simulations were performed to investigate the tensile properties of SCD/TiC combinations with different TiC in-plane grain sizes (d). The results show that d influenced both the elastic and plastic deformation, ascribing to the specific grain boundaries (GBs) network. The Young's modulus of the combinations was found to increase with the increase of d. After yielding, TiC111 partial dislocations emitting from both the GBs and interfaces were observed to cross GBs or pile-up at GBs, among which d had a negligible effect on the planar-slip induced relaxation. Furthermore, it was found the interaction of dislocation-GB and dislocation-dislocation made a great contribution to strain-hardening. For the combinations with d < 8 nm, it was strengthened by piling-up dislocation at GBs, whereas for the larger d, it was dominated by intra- granular dislocation entanglement. Overall, strain localization and micro crack took place at the interfaces due to the absence of plastic mechanism to accommodate strain gradient. This work provided an atomistic insight into the mechanical behaviors in SCD/TiC combinations, offering guidance for interfacial design to improve the mechanical performances in diamond devices.

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