Linking the pressure dependence of the structure and thermal stability to α- and β-relaxations in metallic glasses

Glasses derive their functional properties from complex relaxation dynamics that remain enigmatic under extreme conditions. Although the temperature dependence of these relaxation processes is well established, their behavior under high-pressure conditions remains poorly understood due to substantial experimental difficulties. In this study, we use cutting-edge experimental techniques to probe the pressure evolution of the relaxation spectrum in a Zr_46.8Ti_8.2Cu_7.5Ni₁₀Be_27.5 metallic glass across gigapascal pressure ranges. Our findings reveal two distinct relaxation mechanisms under high pressure: In the β-relaxation regime, compression drives the system with reduced atomic mobility and enhanced structural disorder, without appreciable density changes. Conversely, α-relaxation under pressure promotes density-driven structural ordering that improves thermal stability. Notably, the transition between these regimes occurs at a constant T/T_g,P ratio, independent of applied pressure. These results provide crucial insights for decoupling the competing structural and relaxation contributions to glass stability, establishing a systematic framework for tailoring glass properties through controlled thermomechanical processing.