自然杂志 ›› 2021, Vol. 43 ›› Issue (1): 53-60.doi: 10.3969/j.issn.0253-9608.2021.01.008

• 科技进展 • 上一篇    下一篇

大激活熵是触发非晶合金记忆效应的关键

宋丽建,许巍,霍军涛,王军强   

  1. 中国科学院宁波材料技术与工程研究所,浙江 宁波 315201 
  • 收稿日期:2020-10-27 出版日期:2021-02-25 发布日期:2021-02-25
  • 通讯作者: 王军强,通信作者,国家优秀青年科学基金获得者,研究方向:非晶合金的非平衡特征调控及其对磁电功能特性的影 响。
  • 基金资助:
    *国家重点研发计划项目(2018YFA0703604、2018YFA0703602),国家自然科学基金项目(51922102、 51771216、 51701230、51827801、52001319),浙江省自然科学基金项目(LR18E010002)和宁波市科技创 新2025重大专项(2019B10051)

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

摘要: 非晶/玻璃等非平衡态材料在能量驱动下会逐渐“老化”(ageing),体积和能量状态逐渐降低,这是非平衡态材料的本征特征之一。不同于“老化”的自然演化规律,记忆效应是指非晶合金经历先低温再高温两步退火时,焓或体积会先增加而后降低至平衡态。如果材料或体系达到热平衡态,初态和历史的记忆将被彻底遗忘。半个世纪以来,人们对记忆效应的理解局限于诸如Tool-Narayanaswamy-Moynihan(TNM)模型等唯象层面,对其物理起源仍不清楚。通过研究非晶合金在单步和两步退火中的弛豫规律,发现非晶合金中存在从β弛豫向α弛豫的等温转变现象,并进一步发现大激活熵是触发记忆效应的关键。这些结果对理解玻璃等非平衡态材料的物理本质和精准调控其性能具有重要意义。

关键词: 非晶合金, 弛豫模式, 记忆效应

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.