Advanced Shape-memory Bulk Metallic Glass Composites

由均匀分散的形状记忆晶体构成的块体金属玻璃基复合材料具有高韧性和高强度的先进材料，具有很大的应用潜力。在拟议的项目中，我们将解决一些最重要的悬而未决的问题，这些问题与复合微结构的优化以及由此产生的形状记忆BMGC的机械性能有关。在此过程中，建议的工作重点是制备和表征不同的CuZr基玻璃形成合金。我们的方法包括系统地结合各种最先进的实验技术(例如，在HRTEM中的原位变形，在高能X射线束中的原位变形)，并辅之以有限元模拟，这将使我们能够回答三个基本问题：(1)化学成分和制备工艺对形状记忆晶体的形核和生长过程(即与B2CuZr相形成有关的热力学、动力学和结构方面)有什么影响，从而对微观结构的形成有什么影响？(2)玻璃相的贡献是什么，晶相和晶体-玻璃界面(界面处的应变失配)与整体变形机制的关系？(3)晶体中的形变诱发马氏体相变如何影响玻璃中的剪切带状过程中的整体塑性变形，以及晶体-玻璃界面又如何改变晶体中的马氏体相变？不可逆变形的物理机制，特别是与相变诱导塑性有关的增韧机制将被阐明。该项目的成功实施有望大大促进对形状记忆BMGCs变形机制的理解。作为一个额外的结果，我们将制定指导方针，如何设计和优化具有先进性能的新型、坚固和延展性的BMGC，使实际工程应用变得触手可及。

Bulk metallic glass matrix composites (BMGCs) containing uniformly dispersed shape-memory crystals have a large potential for applications because they constitute advanced materials with high toughness and high strength. Within the proposed project, we will tackle some of the most important unresolved issues related to the optimization of composite microstructures and the resulting mechanical properties of shape-memory BMGCs. In doing so, the suggested work focuses on preparing and characterizing different CuZr-based glass-forming alloys. Our approach consists of a systematic combination of various state-of-the-art experimental techniques (e.g. in-situ deformation in a HRTEM, in-situ deformation in a high-energy X-ray beam) complemented by finite element modelling, which will allow us to answer three fundamental questions: (1) What is the influence of the chemical composition and the fabrication process on the nucleation and growth process of the shape-memory crystals (i.e. the thermodynamic, kinetic and structural aspects related to the formation of the B2 CuZr phase) and thus on the microstructure formation? (2) What is the contribution of the glassy phase, the crystalline phase and the crystal-glass interface (mismatch strains at the interface) to the overall deformation mechanism? (3) How does the deformation-induced martensitic transformation in the crystals affect the overall plastic deformation in terms of the shear-banding process in the glass and how does the crystal-glass interface, in turn, modify the martensitic transformation in the crystals? The physical mechanisms underlying irreversible deformation, especially the toughening mechanisms, associated with the transformation-induced plasticity in the crystals will be elucidated. The successful implementation of the project is expected to lead to a significant advance in the understanding of the deformation mechanisms in shape-memory BMGCs. As an additional result, we will develop guidelines how to design and therefore optimize novel, strong and ductile BMGCs with advanced properties, which bring practical engineering applications within reach.