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

钛铝化物的加工是非常困难的，由于其极端的硬度和脆性在室温下。因此，直到今天，基于TiAl的半成品和部件相当昂贵，因此仅零星使用。然而，在当前对净成形或至少近净成形加工的密集研究领域中预期的进展应导致生产成本的显著降低，并因此导致铝化钛的有利性质的更密集使用，特别是用于高温应用。拟议的研究项目解决了通过反应退火的细层状Ti/Al复合板的TiAl片材的加工。在申请人的指导下，在萨克森卓越计划ECEMP（德累斯顿欧洲新兴材料和工艺中心）资助的一个名为“高强度金属复合材料（HSMetComp）”的研究项目中，开发并优化了通过累积辊压焊进行的生产。Ti/Al复合板的厚度为2.5 mm，包含多达512个Ti/Al相界。层间距约为4 µm，并可通过随后的冷轧进一步减小至400 nm以下。在上述研究项目中，证明了通过相关方法（累积型锻和集束（ASB））生成的Ti/Al多芯丝的反应退火为TiAl/Ti 3Al合金[2]。此外，在初步的研究中，Ti/Al复合板转化为TiAl/Ti 3Al合金的可行性已被证明。该研究项目的目标是全面研究Ti/Al复合板的反应退火。为了优化这一过程，必须研究在界面处的相形成作为在加工期间引入的能量的函数，以及在转变期间材料的微观结构、织构和应力状态的演变。此外，还应表征反应退火后TiAl板材的力学性能。此外，目的是研究先前变形的材料的反应退火，以证明该方法用于生产复杂的近净形半成品部件（例如，配置文件）。

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).