Viscoelasticity and viscosity of Pd–Ni–Cu–P bulk metallic glasses

The dynamic shear modulus was investigated in a Pd 43Ni 10Cu 27P 20 (numbers indicate at.%) bulk metallic glass, in a large temperature range from room temperature up to the supercooled liquid region through the glass transition range. Measurements were performed at various frequencies. The real part of the dynamic shear modulus (i.e. the storage modulus) shows an important decrease due to the main α relaxation, characteristic of amorphous materials. This large decrease is preceded by a secondary relaxation, attributed to short-range movements. The imaginary part of the complex shear modulus reveals associated variations. Experimental results are satisfactorily described using a physical model for the mechanical response of the amorphous material and especially for the characteristic times for the atomic mobility. The same model is used to explain the non-Newtonian behaviour of the viscosity of this metallic glass, as reported by various authors.