超快速热处理制备高强高韧金属非晶复合材料的研究

Metallic glass composites, which is fabricated by in situ introducing second ductile crystals into the glassy matrix, has shown excellent mechanical properties at the room temperature and has been paid great attention in the field of metallic glasses. However, it is very difficult to use traditional preparation methods to effectively control the precipitation of second ductile crystals in the glassy matrix and to further improve mechanical properties of metallic glass composites, which has been a stumbling block for practical structural application. Therefore, the ultra-fast heating and chilling treatment is adapted to in situ fabricate high strong and ductile metallic glass composites in Fe-based and CuZr-based alloys. By controlling annealing process parameters, the formation of nano or micro scale ductile α-Fe in Fe-based alloys or B2 CuZr in CuZr-based alloys, and the content of free volume in glassy matrix can be effectively controlled, respectively. The present project could provide a new strategy to fabricate metallic glasses composites with good deformability. Furthermore, the crystallization kinetics of Fe-based and CuZr-based metallic glasses under ultra-fast heating conditions will be clarified. The changes of free volume in the glassy matrix under different heat treatment conditions will be clearly studied. The correlation between the microstructural features and mechanical properties of the present composites will be systematically investigated in order to provide a deep understanding of the formation and deformation mechanisms of the investigated composites.

通过在非晶基体中原位引入韧性晶体相制备出的金属非晶复合材料由于其优异的室温力学性能，成为非晶合金领域的研究热点之一，但传统的制备工艺并不能非常有效的控制晶体相的析出，不利于此类材料力学性能的进一步提升，极大地限制了其作为结构材料的应用。本项目以铁基和铜锆基非晶合金为研究对象，采用超快速加热和激冷的热处理工艺（即超快速热处理），分别实现对铁基非晶合金中α-Fe韧性晶化相和铜锆基非晶合金中形状记忆性B2 CuZr韧性晶化相形核长大的控制，降低超快速热处理过程中非晶基体中自由体积的湮灭程度，制备出高强高韧铁基和铜锆基非晶复合材料，为非晶复合材料的开发提供一种新的思路。完善在超快速加热条件下的非晶晶化动力学机制，探寻超快速热处理后非晶基体中自由体积的变化规律，揭示变形过程中不同韧性晶体相与剪切带的相互作用，阐明此类复合材料的微观结构和力学性能的内在联系，完善人们对金属非晶复合材料的理解和认知。

尽管金属非晶合金具有许多优异的力学性能，但是由于其塑性变形主要集中在局域化剪切带内的特点，使得非晶合金在变形过程中呈现出室温脆性和应变软化的缺点，极大的限制了非晶合金作为结构材料的应用。本项目从非晶复合材料的结构特点出发，采用实验和模拟相结合的方法，研究了传统凝固工艺和快速退火工艺对金属非晶复合材料力学性能的影响规律，多角度阐明了高强高韧非晶复合材料的形成机理和变形机制。. 第一，针对铜锆基、锆基、钛基、铁基等非晶合金体系进行适当的成分选择和优化，提出了预测非晶形成能力的理论依据，制备出了多种体系的非晶合金，探讨了其非晶形成能力与非晶结构的内在联系，为后续实验提供了理想的实验对象；第二，研究了不同元素添加对于马氏体合金结构及其马氏体转变效应的影响规律，揭示了变形过程中马氏体转变的结构演变过程，阐明了变形过程中马氏体转变的微观机理，为后续制备非晶复合材料提供了理论依据；第三，通过研究非晶及其复合材料在变形过程中的结构演变过程，揭示了变形过程中韧性晶体相与剪切带的相互作用及其剪切带的演变规律，进一步完善了人们对于变形过程中如何抑制剪切带迅速扩展的认知；第四，通过不同手段控制非晶基体中晶体的析出，制备出了具有不同力学性能的非晶复合材料，探讨了其力学性能随外界条件变化的演变规律，阐明了影响其力学性能的关键因素；第五，通过传统凝固手段、传统退火手段和快速退火手段，研究了非晶复合材料中晶体形核长大的变化规律，完善了快速退火过程中的晶化动力学机制，阐明了晶体在不同条件下的析出形貌、体积分数、尺寸大小等参数的演变规律，进而制备出了高强高韧非晶复合材料。. 本项目的研究工作为高强高韧非晶复合材料的开发提供了一种新的思路，对于促进非晶复合材料的发展和应用具有重要意义。