Effect of the fictive temperature on the modulus, hardness, yield strength, dynamic mechanical and creep response of Zr44Ti11Cu10Ni10Be25 metallic glasses

Abstract

Characterizing the dependence of the mechanical properties and structure of metallic glasses on processing parameters and thermal history is of significant importance to understand the nature of glass. One way of defining a specific structural state of a glass is by means of its fictive temperature Tf at which the supercooled liquid falls out of a metastable equilibrium and forms a glass. Since the metastable equilibrium state before quenching is assumed to be well defined, Tf is ultimately thought of as a quantity that describes a specific, reproducibly obtainable structural state. In this research, the effect of systematic variations of an alloy’s structural state, achieved through purposefully setting its Tf, on a range of mechanical properties like modulus, hardness, yield strength, and creep response is studied. Towards this end, amorphous Zr44Ti11Cu10Ni10Be25 samples with different Tf’s were produced and subsequently examined using nanoindentation, dynamic mechanical thermal analysis, and density measurements. It is observed that the lower fictive temperatures directly result in a higher the packing efficiency, i.e., a lower available (‘free’) volume in the glass. The resulting denser atomic packing manifests in increased values for hardness, modulus, and yield strength. These effects were found to be substantial despite the fact that all samples featured the exact same chemical composition and phase.