Pressure effect on the structural relaxation and glass transition in metallic glasses

Two different enthalpy recovery methods were applied to investigate the effects of pressure on structural relaxation and glass transition temperature (T-g) in two metallic glasses (Pd40Ni10Cu30P20 and Zr65Al7.5Cu27.5). The pressure-induced enhancement of T-g (dT(g)/dP) was derived to be 6 K/GPa in Pd40Ni10Cu30P20 glass, while an increment of 50 K/5 GPa was observed in Zr65Al7.5Cu27.5 glass. Activation (formation and migration) volumes of the flow defect were used to interpret the pressure dependence of the structural relaxation and T-g in terms of the free volume model. According to the measured results, the activation volume of relaxation was derived to be 16.7 Angstrom(3) for Pd40Ni10Cu30P20, which is much smaller than that of the polymers. (C) 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.