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Chinese Journal of Nature ›› 2021, Vol. 43 ›› Issue (1): 53-60.doi: 10.3969/j.issn.0253-9608.2021.01.008

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Large activation entropy is a key factor to trigger the memory effect of amorphous alloys

SONG Lijian, XU Wei, HUO Juntao, WANG Junqiang   

  1. Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, Zhejiang Province, China  
  • Received:2020-10-27 Online:2021-02-25 Published:2021-02-25

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Abstract: The enthalpy and volume of materials in metastable states, such as amorphous materials and glasses, always decay simultaneously through an energy-driven process called ‘‘ageing’’. This is one of the intrinsic characteristics of non-equilibrium systems. As opposed to the common monotonic relaxation process of ageing, the memory effect describes an isothermal annealing experiment, in which the enthalpy/volume of a pre-annealed glass first increases before finally decreasing towards equilibrium. If the system reaches its equilibrium state, its memory to the past states will vanish thoroughly. For the past half century, phenomenological models such as the Tool-Narayanaswamy-Moynihan (TNM) model have been used to describe the memory effect, but its underlying physical mechanismsare still not clear. In this paper, the relaxation kinetics in single and two-temperature annealing processes was studied. According to our research, there was a transition from β relaxation to α relaxation in amorphous alloys during isothermal annealing. We further discovered that a large activation entropy (S*) is the key factor to trigger on the memory effect. These results open a gate for understanding the physical origin of non-equilibrium systems and precisely modifying their properties.