Spontaneous strain glass to martensite transition in a Ti ₅₀Ni _44.5Fe _5.5 strain glass

Glass transition has often been considered as a purely kinetics-controlled freezing process, thus it is not expected that a frozen glass state can spontaneously transform into a long-range-ordered (LRO) phase. Here we show evidence for a spontaneous transition from a frozen strain glass (STG) to a LRO martensite in a Ti ₅₀Ni _44.5Fe _5.5 alloy: the alloy freezes into a STG at 179 K, but the frozen STG does not keep frozen and it transforms spontaneously into a LRO martensite (R phase) at 154 K. The transition from a frozen STG (with local R-like order) into a LRO R phase is explained by considering the existence of a thermodynamic driving force towards LRO. The present result indicates that thermodynamics may also play a role in glass, in addition to the kinetics.