不均匀性:非晶合金的灵魂

非晶合金,即金属玻璃,是一类特殊的由基本化学元素组成的非晶态物质,由于其独特的微观组织结构,展现出了不同于传统晶态合金材料的特殊物性,而成为高性能材料应用领域的重要一员.由于非晶合金的结构无序性,且当前精确表征其微观结构的实验手段缺乏,相应的理论模型也不完善,人们对非晶合金中一些基础物理问题的认识尚且不足,无法形成基本的理论框架来精确地描述其物性产生的微观机理.因而,当前非晶合金研究的核心问题可以概括为:如何建立以微观特征或结构为基础的基本理论框架,准确地概括非晶合金物性的微观机理.在过去几十年里,针对非晶合金的大量研究表明,在非晶合金长程无序的特征中,隐藏着本征的不均匀性和有序,且这些不均匀性的特征与材料物性有着密切的关联,使得建立以不均匀性特征为基础的理论框架成为可能.本文从非晶合金微观特征的不均匀性包括静态不均匀性和动态不均匀性的视角出发,概括性地总结了非晶合金材料与物理研究中取得的丰硕成果,及当前需要关注的重要科学问题,并针对未来可能的研究模式进行了展望.

Heterogeneity: the soul of metallic glasses

Owing to the superior mechanical and physical properties, metallic glasses (MGs) have attracted tremendous attention as promising candidates for structural and functional applications. Unfortunately, the ability to form uncontrollable glasses, the poor stability and the unpredicted catastrophic failure stemming from the disordered structure, as the Achilles' heel of MGs, severely restrict their large-scale applications. A number of phenomenological models, such as free volume model, shear transformation zone (STZ) model, flow unit model, etc., have been proposed, intending to relate microstructures to properties of MGs. However, few sophisticated structure-property relationships are established due to a poor understanding of the microstructure of MGs. Recently, heterogeneity is commonly believed to be intrinsic to MGs, and it can be used to establish the structure-property relationship of MGs. In this paper, we review the recent progress of MGs from the angle of “heterogeneity”, including the static heterogeneities and dynamic heterogeneities. The perspectives of the scientific problems and the challenges of metallic glass researches are also discussed briefly.