Break-down of the relationship between α-relaxation and equilibration in hydrostatically compressed metallic glasses

Abstract: Glasses encode the memory of any thermo-mechanical treatment applied to them. This ability is associated to the existence of a myriad of metastable amorphous states which can be probed through different pathways. It is usually assumed that the memory of a glass can be erased by heating the material in the supercooled liquid and that this process occurs on a time scale controlled by the {\alpha}-relaxation. We show, here, that this assumption is not fulfilled in hydrostatically compressed glasses. Applying pressure in the glass state can irreversibly modify the dynamics, thermodynamics and structure of a metallic glass-former, reducing the mobility and leading to important structural modifications resulting in a less stable state than in absence of pressure. When heated above their glass transition temperature, these compressed glasses do not convert into the pristine supercooled liquid, implying the existence of a different process, slower than the {\alpha}-relaxation controlling the equilibrium recovery.