Plastic deformation of single crystals of WSi 2 with the C11 b structure

Abstract

The deformation behavior of single crystals of WSi 2 has been investigated as a function of crystal orientation in the temperature range from room temperature to 1500°C in compression. Single crystals of WSi 2 can be deformed only at high temperatures above 1100°C, in contrast to MoSi 2 in which plastic flow is possible even at room temperature. Four slip systems, {110}〈111〉, {011}〈100〉, {023}〈100〉 and (001)〈100〉, are identified. While the former three slip systems are operative also in MoSi 2, the (001)〈100〉 slip is only operative in WSi 2. The (001)〈100〉 slip in WSi 2 is the alternative to {013}〈331〉 slip in MoSi 2 since they are operative in the same orientation range. Slip on {110}〈331〉 is hardly observed in WSi 2. The values of critical resolved shear stress (CRSS) for the commonly observed slip systems are much higher in WSi 2 than in MoSi 2 with the largest difference for {110}〈111〉 slip. The higher CRSS values in WSi 2 are not only due to the intrinsic difference in the deformation behavior but also due to the existence of numerous grown-in stacking faults on (001).