Memory Effect Manifested by a Boson Peak in Metallic Glass

Abstract

We explore the correlation between boson peak and structural relaxation in a typical metallic glass. Consistent with enthalpy recovery, boson peak shows memory effect in an aging-and-scan procedure. Single-step isothermal aging produces monotonic decrease of enthalpy and boson peak intensity; for double-step isothermal aging, both enthalpy and boson peak intensity experience coincidently an incipient increase to a maximum and a subsequent decrease toward the equilibrium state. Our results indicate a direct link between slow structural relaxation and fast boson peak dynamics, which presents a profound understanding of the two dynamic behaviors in glass. *Corresponding author: pwen@iphy.ac.cn ** Corresponding author: whw@iphy.ac.cn 2 Metallic glasses own distinctive performances in mechanics and magnetics with respect to their crystalline counterparts. With a simple atomic packing, metallic glass offers an effective model system for the study of some controversial issues in glass science [1]. Due to its nonequilibrium nature, glass is continually relaxing toward a metastable equilibrium state, i.e., physical aging [2]. It is fraught with difficulty for modeling of glass aging and understanding its basic mechanisms due to the complex dynamics [3][4][5][6][7][8][9][10]. One peculiar phenomenon in glass aging is the memory effect, viz., during the relaxation toward its equilibrium state, a previously aged glass often shows a temporary neglect of its future (the equilibrium state) and a memory of its past, revealing history-dependent behaviors [11][12][13][14][15]. Memory effect is another manifestation of structural relaxation and ensures the proper description of the relaxation dynamics, thus, procures a deeper understanding of the complex glassy-state dynamics [2,15].Glass puzzles us not only with the localized complex atomic rearrangement arising from its nonequilibrium nature, but also with the peculiar low-frequency (terra is of paramount importance in discriminating between these theoretical models.In this letter, we trace the evolution of the boson heat capacity peak with the structural relaxation manifested by the relative enthalpy change. Upon single-step isothermal aging at a constant temperature, both enthalpy and boson peak intensity show a monotonic decrease toward the metastable equilibrium state. When the sample was firstly aged at a certain temperature and then stepped up to a higher one, an obvious nonmonotonic behavior emerges not only in enthalpy but also, intriguingly, in boson peak intensity, i.e., the memory effect is revealed. The memory effect manifested by boson peak behavior indicates clearly a direct link between the slow structural relaxation and the fast boson peak dynamics and brings a new perspective to the memory effect and the dynamics in glass.The Zr 50 Cu 40 Al 10 bulk metallic glass (BMG) was prepared by suck-casting from master alloy ingots to a copper mold cooled by water in an arc furnace. The pre-aged at a lower temperature before the second step aging, the endothermal...

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