TiAl-based semi-finished products by heat treatment of Ti/Al composite sheets

钛铝化物的加工非常困难，因为它们在室温下具有极高的硬度和脆性。因此，直到今天，TiAl基半成品和组件都相当昂贵，因此仅偶尔使用。然而，预计在当前净形状或至少近净形状加工的密集研究领域的进展将导致生产成本的显著降低，从而导致更广泛地使用钛铝化物的有利性能，特别是在高温应用中。提出的研究项目旨在通过反应退火法加工TiAl薄板，以获得细层的Ti/Al复合材料薄板。在申请人的指导下，他们通过累积滚压的方式生产出了高强度金属复合材料(HSMetComp)，该研究项目由撒克逊卓越计划ECEMP(欧洲新兴材料和工艺研究中心)资助。Ti/Al复合板的厚度为2.5 mm，含有多达512个Ti/Al相界。层间距约为4微米，通过随后的冷轧可进一步减小到400 nm以下。在上述研究项目中，证明了通过相关方法(累积旋压和捆扎(ASB))生成TiAl/Ti3Al合金的Ti/Al多丝反应退火法[2]。在此基础上，初步探讨了将Ti/Al复合板转变为TiAl/Ti3Al合金的可行性。本研究项目的目的是对钛/铝复合材料板材的反应退火进行全面的研究。为了优化这一过程，必须研究界面上的相形成作为加工过程中引入的能量的函数，以及材料在相变过程中的微观结构、织构和应力状态的演变。此外，还需要对反应退火后的TiAl板材的力学性能进行表征。此外，它的目的是研究以前变形的材料的反应退火法，以证明该方法对于生产复杂的近净形状半成品零件(例如型材)的适用性。

The processing of titanium aluminides is exceptionally difficult due to their extreme hardness and brittleness at room temperature. Therefore, until today TiAl based semi-finished products and components are rather expensive and hence are used only sporadically. However, the progress expected in the current field of intense research on net shape or at least near net shape processing should lead to a significant reduction of the production costs and hence lead to a more intensive use of the advantageous properties of titanium aluminides, in particular for high temperature applications. The proposed research project addresses the processing of TiAl sheets via reaction annealing of finely layered Ti/Al composite sheets. Their production by accumulative roll bonding has been developed and optimized [1] under the direction of the applicant in a research project called 'High Strength Metallic Composites (HSMetComp)' financed by the Saxon Excellence Initiative ECEMP (European Centre for Emerging Materials and Processes Dresden). The Ti/Al composite sheets have a thickness of 2.5 mm and contain up to 512 Ti/Al phase boundaries. The layer spacing is about 4 µm and can be further reduced to below 400 nm by subsequent cold rolling. During the above mentioned research project, the reaction annealing of Ti/Al multifilamentary wires generated via a related method (accumulated swaging and bundling (ASB)) into a TiAl/Ti3Al-alloy was proven [2]. Furthermore, the feasibility of the transformation of the Ti/Al composite sheets into a TiAl/Ti3Al-alloy has been demonstrated in a preliminary study. The objective of the proposed research project is a comprehensive study of the reaction annealing of Ti/Al composite sheets. To optimize this process, the phase formation at the interfaces as a function of the energy introduced during the processing has to be investigated, as well as the evolution of microstructure, texture and stress state of the materials during the transformation. Furthermore, the mechanical properties of the TiAl sheets after the reaction annealing should be characterized. In addition, it is the aim to investigate the reaction annealing of previously deformed material to demonstrate the suitability of the method for the production of complex near net shape semi-finished parts (e.g., profiles).