Structural relaxation of nanocrystalline PdAu alloy: Probing the spectrum of potential barriers

Abstract

A commonality between nanocrystalline metals and metallic glasses is their dependence of structure and properties upon preparation history and postprocessing. Depending on preparation conditions, stored excess enthalpy and volume—relative to the crystalline ground state—can vary significantly. Annealing of material states of elevated enthalpy or volume induces structural relaxation and concomitant depletion of excess energy and volume. We analyzed the kinetics of volume relaxation in nanocrystalline PdAu alloys by partitioning the overall process into a set of independent and parallel reactions for arbitrary time-temperature protocols. The obtained spectra of kinetic parameters imply a complex relaxation behavior that violates time-temperature superposition and time aging-time superposition. The analysis will enable to reconstruct the effective energy landscape underlying the relaxation dynamics.