金属玻璃自由体积理论的研究概述  

A State-of-the-art Review on Study of Free Volume Theory in Metallic Glasses

作　　者：时博 王金辉[1] 魏福安 SHI Bo;WANG Jinhui;WEI Fuan(Qinghai Provincial Key Laboratory of New Light Alloys,Qinghai Provincial Engineering Research Center of High Performance Light Metal Alloys and Forming,Qinghai University,Xining 810016)

机构地区：[1]青海大学青海省高性能轻金属合金及深加工工程技术研究中心青海省新型轻合金重点实验室,西宁810016

出　　处：《材料导报》2019年第7期1221-1226,共6页Materials Reports

基　　金：青海省自然科学基金(2018-ZJ-951Q);青海省创新平台项目(2017-ZJ-Y17)~~

摘　　要：金属玻璃具有高强度、高硬度、高弹性应变以及良好的耐腐蚀性,然而,尺寸小、脆性大的缺点严重限制了其广泛应用。自由体积是影响金属玻璃的玻璃转变、塑性变形、结构和性能的关键因素。因此,理清金属玻璃中自由体积理论的发展脉络十分重要。本文首先介绍了自由体积的概念,其次讨论了自由体积与玻璃转变、塑性变形、性能之间的关系,最后总结了自由体积含量的定量化方法。自由体积参与了金属玻璃的玻璃转变和塑性变形等基本过程。由于自由体积处的原子配位数低,与周围区域的机械接合弱,所以在温度或应力的作用下,自由体积处容易发生结构扰动。研究表明,玻璃转变是一个依赖自由体积的动力学过程。当约化自由体积含量达到某一临界值时,开始发生玻璃转变。此外,自由体积理论也被用于解释金属玻璃的塑性变形。在自由体积的协助下,金属玻璃中的原子发生跃迁,进而实现塑性变形。而当自由体积含量达到某一临界值时,宏观变形局域化发生,即产生剪切带。分子动力学模拟、理论计算、透射电镜观察、声发射监测、剪切带热焓测试、密度测量等大量研究结果表明,剪切带上拥有大量的自由体积。自由体积可以通过微合金化、塑性变形、离子束照射、提高冷却速率和降低吸铸电弧功率等多种方式促进产生。一般自由体积含量越高,就会有更多产生剪切带的区域,进而导致多重剪切带产生;同时金属玻璃粘度降低,原子移动能力增加,因此金属玻璃塑性随之增加。由于自由体积处的原子排列疏松,弹性模量较低,所以抵抗变形的能力较弱,因此金属玻璃的强度和硬度将随自由体积含量增加而降低。此外,自由体积还会影响金属玻璃的原子扩散速率和热稳定性等。定量自由体积含量的方法主要有:(1)热分析法。通过计算结构驰豫过程的放Metallic glasses feature high strength,high hardness,high elastic strain and satisfactory corrosion resistance.However,suffering from small dimension and high brittleness,metallic glasses can hardly realize widespread application.Free volume plays a crucial role in affecting the glass transition,plastic deformation,structure and properties of metallic glasses.Accordingly,it is of great significance to straighten out the development of free volume theory.In this work,we firstly introduce the concept of free volume,then discuss the relationship of free volume with glass transition,plastic deformation and properties,finally summarize the quantitative methods for free volume evaluation.Free volume is involved in basic processes of glass transition and plastic deformation of metallic glass.Due to low coordination number and weak mechanical bonding with the surrounding matrix,structural disturbance is prone to occur at free volume sites of metallic glasses under the actions of temperatures and stresses.Glass transition is demonstrated to be a dynamic process which is largely depended on free volume.Glass transition occurs when the reduced free volume content reaches a certain critical value.Besides,the plastic deformation mechanism of metallic glass can be also explained by free volume theory.The atomic transition and further plastic deformation can be realized with the assistance of free volume.Moreover,when the free volume content reaches a certain critical value,the localization of macroscopic deformation appears,namely,shear bands generate.It has been proved by molecular dynamics simulation,theoretical calculation,transmission electron microscopy,acoustic emission monitoring,enthalpy measurement and density measurement that there exist a large amount of free volume in shear bands.Generally speaking,free volume can be produced by microalloying,plastic deformation,ion beam irradiation,increasing the cooling rate,and decreasing the arc power.It is commonly believed that higher free volume content results in more sites

关 键 词：金属玻璃 自由体积 玻璃转变 塑性变形 

分 类 号：TG139.8[一般工业技术—材料科学与工程]