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

由于钛铝化物在室温下具有极高的硬度和脆性，因此其加工异常困难。因此，直到今天，基于TiAl的半成品和组件相当昂贵，因此只偶尔使用。然而，目前对净形状或至少接近净形状加工的深入研究有望取得进展，这将导致生产成本的显著降低，从而导致更密集地利用钛铝化物的优势特性，特别是在高温应用中。提出的研究项目是通过反应退火的精细层状Ti/Al复合片加工TiAl板。在“高强度金属复合材料（HSMetComp）”研究项目的指导下，该项目由撒克逊卓越计划ECEMP（德累斯顿新兴材料和工艺欧洲中心）资助。Ti/Al复合片的厚度为2.5 mm，包含多达512个Ti/Al相界。层间距约为4 μ m，通过后续冷轧可进一步减小至400 nm以下。在上述研究项目中，通过相关方法（累加挤压和捆扎（ASB））生成的Ti/Al多丝线反应退火制备了TiAl/ ti3al合金[2]。此外，还对Ti/Al复合板材转化为TiAl/ ti3al合金的可行性进行了初步研究。本课题的目的是对Ti/Al复合板材的反应退火进行综合研究。为了优化这一过程，必须研究加工过程中引入的能量对界面相形成的影响，以及相变过程中材料的微观结构、织构和应力状态的演变。此外，还需要对反应退火后TiAl片材的力学性能进行表征。此外，目的是研究先前变形材料的反应退火，以证明该方法适用于生产复杂的近净形状半成品零件（例如，型材）。

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).