Plastic deformation of single crystals of NbSi2 with the C40 structure

The deformation behavior of single crystals of NbSi2 with the C40 structure has been investigated as a function of crystal orientation in the temperature range from room temperature to 1500°C in compression. Plastic flow is possible only when slip along 〈12̄10〉 on (0001) is operative and no other slip systems are observed in the whole temperature range investigated. While plastic flow is observed above 500°C for as-grown crystals, the onset temperature for plastic flow is lowered by 300°C when the crystal is prestrained at 1400°C and then re-deformed at low temperatures. The critical resolved shear stress (CRSS) for basal slip decreases with increasing temperature but exhibits a moderate peak around 1300°C. In the temperature range where the anomaly in the CRSS is observed, the stress-strain curve is usually accompanied by serration. The deformation mechanism of NbSi2 is discussed in comparison with that reported for isostructural CrSi2.