On the shear modulus and thermal effects during structural relaxation of a model metallic glass: Correlation and thermal decoupling.

• Effects of sub-T g annealing and HPT on relaxation were comparatively studied. • Relaxation behavior was studied by in-situ shear modulus and modulated DSC. • Reversible and nonreversible components of relaxation were identified. • The heat flow can be well correlated with the shear moduli for all states. • Interconnection between atomic motion, thermal effect and shear elasticity was discussed. Pd 40 Ni 40 P 20 (at.%) samples with different enthalpy states were fabricated through high-pressure torsion or sub- T g annealing of the as-cast material. Subsequently, the underlying structural relaxation was studied by in-situ shear modulus measurements and modulated differential scanning calorimetry. The results show that high-pressure torsion leads to shear modulus softening and an increase of the nonreversible exothermic enthalpy, indicating a significant structural rejuvenation, while sub- T g annealing causes shear modulus hardening and a decrease of the nonreversible exothermic enthalpy. The reversible endothermic effect which can reflect the fractional change of supercooled liquid with temperature was found to be almost identical for all samples, and independent of deformation or thermal history. The total heat flow can be well correlated with the shear modulus within the framework of interstitialcy theory. Furthermore, we demonstrate that the structural relaxation below T g decouples into internal stress relaxation and β-relaxation. In addition, this work indicates that the processes of α-relaxation and β-relaxation in the metallic glass are of similar structural origin but occur on different spatial scales. [Display omitted] [ABSTRACT FROM AUTHOR]