SINGLE-CRYSTAL ELASTIC-CONSTANTS OF NBSI2

Room-temperature elastic properties of hexagonal C40 NbSi2 single crys tal have been determined using resonant ultrasound spectroscopy (RUS). All five independent elastic stiffness constants c(ij) were obtained: c11 = 380.2, c33 = 468.0, c44 = 145.3, c12 = 75.9 and c13 = 88.3 GPa. The shear modulus c66 in the (0001) plane, 152.2 GPa, is low relative to those of MoSi2 and WSi2. The isotropic elastic constants for polyc rystalline material were also calculated. The results show that the bu lk modulus K, shear modulus G and Young's modulus E are much higher th an those of the constituent elements. The room temperature Poisson's r atio of the compound is 0.18, which is much smaller than those of the constituent elements and most observed materials. The elastic properti es of C40 NbSi2 and C11b MoSi2 and WSi2 are compared and the possible influence on the mechanical behaviour is discussed.