Development of a Powder Based Manufacturing Route for Affordable Titanium Aluminide Sheet for Nacelle Engine Applications

金属间钛铝化物（TiAl）基合金提供低密度、高温下的高强度、良好的抗氧化性和热气体腐蚀性的良好组合，为结构航空航天应用和汽车涡轮增压器应用提供优异的工程性能。它们已在最近的应用中得到验证，例如GEnx商用飞机发动机（波音787）中的低压涡轮机（LPT）叶片。TiAl基合金为航空结构高温应用提供了独特的性能，可以取代较重的镍基高温合金。许多潜在的未来应用将需要片状形式的TiAl基合金，这需要均匀的铸锭原料、挤压/锻造和受控的热轧和冷轧计划。TiAl基合金从铸锭的多道次计划是具有挑战性的，因为由于铸造过程中的微观偏析，工艺窗口非常窄。因此，需要进一步的研究来增加粉末冶金路线中TiAl基合金在更广泛的结构航空航天应用中的使用，例如发动机机舱部件，这些部件正在达到其操作极限。从该EngD/PHD产生的输出将提供对这种合金的加工的进一步信心，期望从粉末获得这种片材产品的较低成本加工路线。这将最终有助于减少燃料消耗，并使航空和航天运输更加环保。在这个激动人心的EngD/PHD项目中，固态粉末路线，如热等静压和场辅助烧结，将与受控的热轧和冷轧结合使用，以确定粉末特性和合金成分对（1）热轧和热机械加工特性以及（2）微观结构和性能发展的影响。在第一种情况下，将采用不锈钢包装和加热辊进行叠轧，以提高延展性，减少氧化和降低开裂敏感性。将使用有限元建模软件将热机械加工、平面应变轧制参数与显微组织演变相关联。热轧后加工，如冷轧和超塑成形将与上游的粉末基、热轧路线有关。

Intermetallic titanium aluminides (TiAl) based alloys provide a good combination of low density, high strength at elevated temperatures, good oxidation and hot gas corrosion resistance, providing excellent engineering properties for structural aerospace applications and automotive turbocharger applications. They have been proven in recent applications, such as the low-pressure turbine (LPT) blades in the GEnx commercial aircraft engine (Boeing 787). TiAl based alloys provide unique properties for aerostructural high temperature applications and can replace heavier nickel-based superalloys. Many potential future applications will require TiAl based alloys in sheet form which requires homogeneous ingot feedstock, extrusion/forging and controlled hot and cold rolling schedules. Multi-pass schedules for TiAl based alloys from ingot is challenging, as process windows are very narrow due to micro-segregation during the casting process. And therefore, further research is needed to increase the use of TiAl based alloys from powder metallurgy routes in wider structural aerospace applications, such as engine nacelle parts, which are reaching their operating limits. Outputs generated from this EngD/PHD will provide further confidence in the processing of such alloys with aspirations of a lower cost processing route for such sheet product from powder. This will ultimately contribute to reduced fuel consumption and make air and space transport greener. In this exciting EngD/PHD project, solid state powder routes, such as hot isostatic pressing and field-assisted sintering, will be used in conjunction with controlled hot and cold rolling to determine the effects of powder characteristics and alloy composition on the (1) hot rolling and thermomechanical processing characteristics and (2) microstructure and property development. In the first instance pack rolling in stainless steel packages and using heated rolls will be applied - to enhance the ductility, reduce oxidation and reduce cracking susceptibility. FE modelling software will be used to correlate thermomechanical processing, plane strain rolling parameters with microstructural evolution. Post hot rolling processing, such as cold rolling and superplastic forming will be related to the upstream powder-based, hot rolling route.