Plastic yielding of glass in high-pressure torsion apparatus

Hardness measurements performed at room temperature have demonstrated that glass can flow under elevated pressure, whereas the effect of high pressure on glass rheology remains poorly quantitated. Here, we applied a high-pressure torsion apparatus to deform SCHOTT SF6((R)) glass and attempted to quantitate the effect of pressure and temperature on the shear deformation of glass subjected to pressures from 0.3 to 7 GPa and temperatures from 25 to 496 degrees C. Results show that the plastic yield deformation was occurring during the HPT experiments on the SF6 glass at elevated temperature from 350 to 496 degrees C. The yield stress of SF6 glass decreases with increasing temperature and decreasing pressure. An extended Arrhenius model with one set of parameters, namely infinite yield stress Y-0 = 0.17 +/- 0.1 GPa, activation energy E-a = 4.8 +/- 0.5 kJ/mol and activation volume V-a = 1.4 +/- 0.2 cm(3)/mol, can explain the experimental results well.