Unusual secondary slip activity at room temperature in VC single crystals

[Display omitted] •In situ scanning electron microscopy (SEM) based uniaxial compression tests were conducted on 001, 110, and 111 oriented vanadium carbide (VC) single-crystals.•In addition to primary slip systems, secondary slip systems with lower Schmidt factors were observed to be active at room-temperature.•Critical resolved shear stresses for all the three primary slip systems are nearly the same. Intriguingly, 110-oriented crystals exhibit brittle failure while both 001 and 111 oriented crystals deform plastically with strains exceeding 20%.•For the first time, we present direct evidence for the activation of secondary {111}〈11¯0〉 during uniaxial compression not only along [001] but also along [111] in TMC crystals. Cubic transition-metal carbides are high-melting compounds with remarkable high-temperature mechanical properties but are generally considered to be brittle at low-temperatures. Here, we report on the activation of multiple slip systems and plasticity in 001, 110, and 111 oriented vanadium carbide (VC) single-crystals subjected to uniaxial compression at room-temperature. Using in situ scanning electron microscopy based mechanical testing, we observe plastic strains up to 21%, size-dependent yielding, and work hardening in VC(001) and VC(111). In comparison, VC(110) crystals are relatively brittle with limited localized plasticity. VC(111) crystals exhibit the highest yield strengths of up to ∼23 GPa while VC(001) crystals are some of the softest with yield strengths as low as ∼13 GPa. For loading along [110], we find that only the primary slip system, {111}〈11¯0〉, is active. In VC(001) and VC(111), we find the operation of two sets of slip systems, [{110}〈11¯0〉 and {111}〈11¯0〉] and [{111}〈11¯0〉 and {100}〈11¯0〉], respectively. Intriguingly, the estimated critical resolved shear stresses for all the three slip systems are nearly the same. Our results, which reveal orientation-dependent differences in the activity of the same slip system, provide new insights into plastic deformation in refractory compounds.