钛基块体非晶合金热塑性成形性能与成形机理研究

Bulk metallic glasses (BMGs) have attracted much attention due to their outstanding properties such as high strength, high hardness and so on. Moreover, due to the thermoplastic forming ability in supercooled liquid region, metallic glasses are very suitable for the synthesis of parts with complicated shapes (especially micro/nano structures). However, only a few inert noble metal based (e.g. Pd, Pt and Au-based) and Zr-based BMGs possess good thermoplastic formability. It is necessary to perform research on thermoplastic forming of other low-cost BMGs. In this project, lightweight high strength Ti-based BMGs are selected as starting alloys. A physical model will be developed to predict the thermoplastic formability of Ti-based BMGs. Alloying method will be adopted to improve the thermoplastic formability of Ti-based BMGs and the effects of alloying elements on the thermoplastic formability will also be investigated systematically. Then the oxidation behavior of newly developed Ti-based BMGs in the supercooled liquid region will be studied. Based on the above researches, the thermoplastic forming mechanism of Ti-based BMGs will be clarified in detail. A novel strategy will be proposed to reduce the entering barriers caused by surface oxidation. Finally detailed studies will be carried out on the effect of thermoplastic forming processing parameters on the accuracy, microstructure and properties of the formed parts. The success of the present research project can break through the bottleneck of thermoplastic forming of reactive Ti-based BMGs in air, and consequently extend considerably the application scope of Ti-based BMGs.

非晶合金不仅具有高强度、高硬度等优异性能，而且在过冷液相区内具有优异的热塑性成形性能。因此采用非晶合金精确成形制备复杂形状的零件（尤其是微纳米件）极具应用前景。目前用于热塑性成形的非晶合金体系为少数惰性贵金属基（如钯基、铂基、金基）和锆基非晶合金体系，因此，很有必要研究其它低成本非晶合金的热塑性成形性能。本项目拟选用轻质高比强度钛基非晶合金为研究对象，构建钛基非晶合金热塑性成形性能预报物理模型，研究合金成分和工艺因素对钛基非晶合金热塑性成形性能的影响规律和影响机制，揭示影响钛基非晶合金热塑性成形性能的关键因素；认识钛基非晶合金的粘滞流变行为特征和表面氧化膜形成规律及其对热塑性成形性能的影响，提出抑制氧化膜生成方法；最后建立热塑性成形工艺参数与钛基非晶合金成形件的精度、结构与性能间的关系。本项目研究成果对突破低成本非晶合金大气环境下热塑性成形加工瓶颈，拓展其工程应用范围具有重要意义。

钛基非晶合金具有高比强度等优异性能，有望应用于航空航天等诸多领域。但有限的热塑性成形性能极大地制约了其广泛应用。本项目针对钛基非晶合金热塑性成形性能及成形机理等基础问题开展研究。系统研究了合金元素种类、合金化方式和合金元素添加量对钛基非晶合金热塑性成形性能的影响规律，发现采用Co、Fe等合金元素替换Ti-Zr-Be体系中的Be能综合改善合金的非晶形成能力、室温力学性能和热塑性成形性能，研发出具有良好热塑性成形性能的新型轻质高比强度钛基非晶合金；发现基于合金热力学温度的S参数能有效钛基非晶合金的热塑性成形性能，研究了钛基非晶合金物理、化学参数对热塑性成形性能的影响，建立了基于BP人工神经网络的钛基非晶合金热塑性成形性能预测模型，实现了钛基非晶合金热塑性成形性能的有效预测；发现钛基非晶合金过冷液相区粘滞流变行为具有尺寸效应，在高温变形条件下由不同尺寸试样的比表面积差别所引起的自由体积湮灭量差异是导致非晶合金热塑性成形的尺寸效应的主要原因之一，建立了考虑尺寸效应的钛基非晶合金热塑性本构模型；研究了钛基非晶合金等温和非等温晶化动力学系行为，绘制了钛基非晶合金晶化转变TTT曲线，基于改进的Hagen-Poiseuille公式和Karman公式建立了钛基非晶合金纳米压印成形图，针对纳米压印成形中存在的结构不均匀和表面氧化问题，采用润滑层辅助纳米模压技术，成功实现了大气环境下钛基非晶合金纳米结构的可控制备。此外，本项目还探索了钛基非晶合金大尺寸零件的制造方法，提出了增材/锻造复合成形等新工艺。项目成果对突破钛基非晶合金成形技术瓶颈，促进其广泛应用具有重要意义。