Kovacs-like memory effect and relaxation spectrum in metallic glasses

Linking history-dependent mechanics of metallic glasses to microscopic relaxation modes remains a major challenge. This work reports the first systematic discovery of a stress-history-driven Kovacs-like memory effect in a LaCeNiAl metallic glass, which manifests as a non-monotonic strain response under two-step loading and a complex double non-monotonic behavior under three-step loading. The core innovation is a unified independent strain contribution superposition model based on an experimentally determined power-law relaxation spectrum. This framework successfully deconstructs complex mechanical histories into the temporal competition of distinct internal relaxation modes. Furthermore, we elucidate the microscopic origin of the spectrum by mapping macroscopic relaxation modes onto localized structural excitations embedded within the potential energy landscape. By bridging macroscopic mechanical memory with microscopic dynamic heterogeneity, this work provides a predictive framework for understanding non-equilibrium dynamics in disordered solids.