A dynamic map of metallic glasses
Abstract
Recent decades have witnessed substantial progress in understanding relaxation dynamics of metallic glasses (MGs), marked by the discovery of multiple intrinsic dynamic modes and their correlation with properties. These advances have deepened microscopic insight into the nature of glasses and opened new avenues for addressing challenges in MGs design and property modulation. In this MRS Bulletin contribution, we summarize the dynamic modes in MGs, including structural α relaxation, slow β relaxation, nearly constant loss, fast β′ relaxation, γ relaxation, liquid-like fast dynamic mode, surface dynamic mode, vibrational excitations (boson peak and phonon-like modes), and ultraslow dynamic modes. We discuss their microscopic origins, with emphasis on the cooperative atomic motions that give rise to an emergent dynamic spatiotemporal ordering. We further highlight how these dynamic modes govern mechanical behavior, functional properties, stability and processing of MGs, demonstrating that the reliable dynamics–property relationship can help develop new MGs with tailored properties, analogous to structure–property relationships in crystalline materials. We also outline open questions regarding potential unified frameworks for these modes and the prospects for deliberately controlling dynamic modes to overcome property tradeoffs.