复相非晶的微观结构与力学性能调控

Plastic deformation of metallic glasses (MGs) below the glass transition temperature is inhomogeneous with formation of highly localized shear bands, resulting in rapid propagation of shear bands across the samples and premature fracture. The lack of macroscopic plasticity therefore is the main barrier for their application as engineering materials. To circumvent this problem, various approaches have been developed, including adding or in situ precipitating crystalline phases in the MG matrix, enhancing the poisson’s ratio, introducing a large amount of free volume, and producing structural heterogeneity. Phase separation structure as a type of structural heterogeneity, it can enhance the plasticity effectively. So far, however, the investigation about modification of microstructure and mechanical properties in phase separated MG is rare. This project plans are to study the detailed mechanism for formation of phase separation, to investigate the relationships among alloy composition, phase separation structure and plasticity, and to explore microstructure and mechanical property evolutions of phase separated MG subjected to severse plastic deformation. These studies provide theoretical basis for broadening application of MGs and developing their deep processing technology.

非晶合金在玻璃转变温度以下进行不均匀塑性变形，容易沿主剪切带方向过早断裂，呈现出较差的塑性，制约了其作为工程结构材料的应用。为此，发展了各种改善非晶合金塑性的方法，包括非晶基体外加或内生晶态相、提高泊松比、在非晶中引入更多自由体积、引入微观结构的不均匀性等。相分离结构作为一种不均匀的微观结构，能有效地提高非晶合金的塑性。然而，迄今为止关于调控复相非晶合金的微观结构和力学性能的研究十分缺乏。本申请项目拟研究非晶合金相分离的形成机制，探讨合金成分、相分离结构与塑性的关联性，考察复相非晶合金在大塑性变形过程中的结构与力学性能的演化，为拓展这类材料的应用和发展深加工技术提供理论依据。

块体非晶合金的室温塑性差一直是制约其作为结构材料的主要因素。为此，本项目通过合金化方法调控非晶合金的微观结构，获得具有良好塑性的Zr-Cu-Al-M (M=Sn, Co)和Zr-Cu-Ni-Al-M (M=Ag, Ti)块体非晶合金。采用X射线衍射仪、扫描电子显微镜、高分辨电镜、差示扫描量热仪、万能力学试验机、电化学工作站等分析测试了合金的非晶形成能力、微观结构、力学性能及耐蚀性能。结果发现，合金体系的化学混合焓大，对应成分的组元间作用力强，非晶形成能力高；而添加正混合热元素有利于相分离结构的形成，其成分波长随添加量的增加而增大，与此同时，非晶形成能力和热稳定性不断降低。压缩变形中相分离结构有效地促进剪切带的增殖与分叉，提高合金的塑性变形能力。另外发现，非晶相中存在二十面体有序团簇结构时，自由体积分布不均匀，两者协同作用促进变形中多重剪切带的产生。易形成致密钝化膜元素含量愈多，耐蚀性愈佳；塑性变形诱发自由体积的不断产生，加速点蚀发生，从而降低非晶合金的耐蚀性能。