Shear viscosity of the Pd$_{40}$Cu$_{40}$P$_{20}$ metallic glass under conditions of isochronous heating below the glass transition temperature

The shear viscosity is measured under conditions of isochronous (linear) heating below the glass transition temperature of the Pd$_{40}$Cu$_{40}$P$_{20}$, metallic glass, which is characterized by the polymorphic crystallization into the Pd$_2$Cu$_2$P tetragonal phase with a lower density than the initial glass. It is shown that the rate dependence of the shear viscosity can be interpreted as a result of the irreversible structural relaxation by analogy with the case of the previously studied metallic glasses despite the unusual ratio of the densities of the material in noncrystalline and crystalline states.