Influence of carbon content on physicomechanical characteristics of boron carbide

Temperature and amplitude dependences of dynamic shear modulus (SM) and of internal friction (IF) have been measured on boron carbide samples with different carbon content. The samples were investigated at frequencies of torsion oscillations from 0.5 to 5 Hz and at amplitudes of oscillatory deformation from 5×10−6 to 1×10−2 at temperatures from 80 to 1000 K. It was shown that absolute values of SM, of critical amplitudes of oscillatory deformation and of shear elastic limit decreased with the decrease of carbon content in the samples. Simultaneously, activation energy of the intensive relaxation-type IF in the vicinity of 450–470 K was also decreased. Cyclic deformation at 1000 K provided additional decrease to physicomechanical characteristics while at annealing in vacuum at the temperatures of 1273 and 1773 K these structure-sensitive properties significantly increased. The observed changes of physicomechanical characteristics were attributed to possible changes of inter-atomic forces in the structure of boron carbide samples.