Quantifying contribution of hierarchically correlated shear microdomains underlying creep in metallic glass

Abstract

Investigation of the strain evolution of a Cu46Zr47Al7 metallic glass (MG) was conducted through creep deformation encompassing various temperature and stress conditions. The fundamental framework of atomic motion was established through hierarchically dynamic correlation. By discerning a transition in strain rate from three to two regions under cyclic loading conditions, we effectively identified the two underlying mechanisms of creep. The initial deformation mechanism is associated with τ-defects (shear microdomains, SMDs) characterized by a high degree of atomic correlation. This mechanism entails both reversible deformation within a short temporal span and irreversible deformation over an extended duration. Remarkably, the atomic correlation of SMDs remains nearly unaffected by variations in stress and temperature. Furthermore, a fundamental intrinsic correlation emerges between the atomic correlation of SMDs and the defect concentration as ascertained through the framework of quasi-point defect (QPD) theory. The second deformation mechanism entails irreversible deformation attributed to structural relaxation, exhibiting a relatively diminished atomic correlation. In this mechanism, the correlation of atomic motion exhibits a decline with rising temperatures, while remaining relatively less influenced by mechanical effects. Meanwhile, after annealing treatment, the deformation strength associated with structural relaxation significantly decreases. Our study sheds light on the underlying mechanisms of creep in MGs, compensates for the shortcomings of QPD theory in describing long-term creep and provides insights into the fundamental atomic-scale processes governing the mechanical behavior of MGs.