Thermal History Dependent Aging Dynamics in a La-Based Metallic Glass

The atomic dynamics in metallic glasses (MGs) are closely related to their stability. Due to weak resistance to nanocrystallization at high temperatures, we interestingly observe the slow atomic dynamics happening in an as-quenched La-Al-Ni MG sample compared with a sub-Tg pre-annealed one when cooling from about 0.99Tg (Tg the glass transition temperature). An intermittent aging behavior also appears in the as-quenched MG sample only on cooling but not on heating, nor does it appear in the pre-annealed sample on both cooling and heating, indicating that it could be thermal history dependent and related to the existence of nanocrystals. Differently, a sudden atomic dynamics transition from fast to slow is observed in the pre-annealed MG sample when the pre-annealing temperature is approached upon cooling, resulting from the configuration recovery to a low energy state created by pre-annealing. Our findings demonstrate that the thermal history can give rise to significantly different aging dynamics of MGs , providing an in-depth understanding of structural relaxation in disordered materials on the atomic level.