Room-temperature plasticity and size-dependent mechanical responses in small-scale B1-NbC(001) single-crystals

Valence electron concentration as key parameter to control the fracture resistance of refractory high-entropy carbides

“…The observation is consistent with pioneering studies on group V carbides that inferred preferential slip on {111} planes via analysis of hardness anisotropy ( 58 , 59 ). Recent micropillar compression experiments also show increased dislocation mobility on {111} planes of group V, in comparison to group IV, carbides ( 32 , 33 , 60 ). We note that lattice slip on {111} planes may improve ductility by providing enough independent slip systems, according to criteria by von Mises ( 61 ).…”

“…For example, the absence of native defects (such as dislocations and grain boundaries) and very high strain rates used in atomistic simulations return values of strength and elongation at fracture that are much larger than in most experiments. The experimental compressive strength of submicrometer monolithic binary carbides reaches ≈20 GPa ( 32 , 33 ). Such high values (accidentally close to AIMD theoretical strengths σ T ; table S2) are due to the high ceramic resistance to compression and low density of native defects in submicrometer single-crystal samples.…”

Understanding the Role of 1/2 ⟨110⟩ Dislocations in Deformation Mechanisms of Single-Crystal High-Entropy Carbide Ceramics from Machine Learning Force Field Simulations

“…Experimental and theoretical studies extensively document slip systems in cubic monocarbide ceramics, − yet HECCs receive scant attention in this context. , For instance, TiC exhibits {110}⟨10⟩ and {111}<10> as viable slip systems at low and high temperatures, respectively. , ZrC’s {100}⟨110⟩ slip system is identified as softer compared to its {110}⟨10⟩ counterpart . Moreover, NbC demonstrates a preference for the two slip systems: {110}⟨10⟩ and {111}⟨10⟩, attributed to variations in microcompression at ambient conditions . Similarly, HfC and TaC predominantly slip along {110}⟨10⟩ at elevated temperatures, indicating a complex interplay of slip systems influenced by temperature and structural nuances in single-carbide ceramics.…”

“…50 Moreover, NbC demonstrates a preference for the two slip systems: {110}⟨11̅ 0⟩ and {111}⟨11̅ 0⟩, attributed to variations in microcompression at ambient conditions. 51 Similarly, HfC and TaC predominantly slip along {110}⟨11̅ 0⟩ at elevated temperatures, 49 indicating a complex interplay of slip systems influenced by temperature and structural nuances in single-carbide ceramics. In the exploration of the most favorable slip system for (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )C ceramics, we meticulously analyzed three low Miller index planes: (100), (110), and (111), deemed potential candidates for slip planes.…”