Decoupling In Rejuvenated Metallic Glasses

Metallic glasses(MGs)are state-of-the-art metastable metallic materials with excellent mechanical,physical,and chemical properties.Regulating energy state has now become an efficient pathway to tailor the performance of metallic glass due to the intimate relationship between the energy state and the material property.However,there is a coupling relationship between the energy state and the performance of MGs.Precisely,a higher energy state corresponds to better ductility,lower corrosion resistance,and an inferior soft magnetic performance,and vice versa.Conventional routines for regulating the energy state,such as relaxation and rejuvenation,cannot get rid of the coupling relation,resulting in the stagnation of the optimization for multiple properties in MGs.It is,therefore,of great significance to develop an advanced methodology of tuning the energy state to decouple the association between the energy state and the property in terms of the advance in the novel MGs.In this work,we utilized Au50Cu25.5Ag7.5Si17,Zr51(Cu90Ni10)40.5Al8.5,and Fe77.5Si9.5B13 MGs to investigate the influence of rejuvenation by enthalpy relaxation on the energy-state-property coupling.The underlying mechanisms of the decoupling of the energy state and the performance were revealed to offer guidance for optimizing multiple properties of MGs.Rejuvenation by enthalpy relaxation is an annealing process enabling the boost of the energy state,where the relaxed MG is reheated to the temperature that enthalpy relaxation occurs(i.e.,the temperature is above the prior relaxation temperature but below the glass transition temperature),and quenched in sequence,and is capable of tailoring the energy state of MGs in a controllable fashion.The present work investigates the impact of processing parameters on the increment of energy of the Au50Cu25.5Ag7.5Si17 MG,such as the heating rate,the energy state of the pre-relaxed MG,the rejuvenation temperature Trej.,and the cycling number.With an increasing value of Trej.,the energy of the Au50Cu25.5Ag7.5Si17 MG processed with rejuvenation by enthalpy relaxation increases monotonically.At the same time,the hardness variation shows a trend of first decreasing and then rising,and the plasticity variation displays a trend of first increasing and then decreasing.These experimental results confirm that rejuvenation by enthalpy relaxation enables the decoupling between the energy state and the mechanical property.Based on the analysis of relaxation activation energy,the anomalous phenomenon in which hardness increases with increasing energy state is associated with the re-activation of α-relaxation,which can be attributed to the preferential generation of anti-free volume in the percolating liquid-like zone constrained by solid-like zone under the compressive stress state that is induced by rapid heating and cooling.Based on of the three-point bending testing of Zr51(Cu90Ni10)40.5Al8.5 MG,the present work investigates the impact of rejuvenation on macroscopic mechanical properties.For the Zr-based MG processed with rejuvenation at 685 K,the relaxation enthalpy is 0.59 kJ·mol-1 lower than that of the as-cast MG,while the ductility is comparable to the as-cast counterpart.This shows the success of creating bulk MGs with a low energy state but high ductility.With a futher increase in the Trej.,the energy state of MGs continuously increases while the plasticity dramatically decreases.The density change induced by rejuvenation suggests that the formation of anti-free volume should be responsible for the abnormal decrease of ductility with the increasing energy state.Rejuvenation by enthalpy relaxation can creating bulk MGs with a low energy state but high ductility,and the present work rejuvenates the amorphous Fe77.5Si9.5B 13 ribbon for the synergetic optimization of mechanical and soft magnetic properties.For the pre-annealed amorphous Fe-based ribbon after rejuvenation at 694 K,the energy state significantly boosts.Meanwhile,the average bending failure strain increases from 14.9%to 56.1%,and the coercivity decreases from 2.7 to 1.6 A·m-1,showing a simultaneous improvement of plasticity and soft magnetic property.Based on the analysis of stress release and the autocorrelation function,the exceptional decrease in the coercivity with the increasing energy can be attributed to the unceasing relief of quenching stress and the annihilation of crystal-like order after rejuvenation.