Mechanical-Properties Prediction Module for the Development of Powder Processed LPT Blade in TiAl Alloys

In order to accelerate the development of TiAl LPT blade in jet engines and reduce the extensive experimental efforts, some computational approaches to predict the required mechanical properties, in addition to the module to specialize the alloy composition to be able to control microstructure, are needed. We built up the sophisticated materials integration system for the inverse problem consisting of two modules of mechanical-properties prediction (MPM) and microstructure design (MDM). In the presentation, then, focus is places on the MPM how the ultimate tensile strength (UTS) can be predicted. Note that the output of this module is a concrete value of the microstructural constituent governing the property. Therefore, the quantitative analysis by digitalizing the microstructural constituents in needed as one of the databases (DB) of the module. Another important DB to predict the UTS is the work hardening rate of the microstructural constituents. There are two important microstructural constituents in the alloys: one is the lamellar microstructure consisting of α₂-Ti₃Aland γ-TiAl phases and the other the cellular microstructure consisting of β-Ti and γ phases, since we revealed the introduction of the cellular microstructure is effective in increasing the mechanical properties. Then, volume fraction of this β/γ cellular microstructure (<i>V</i>_c) was quantitatively analyzed from back-scattered electron images took from a scanning electron microscope by an image analysis software. The work hardening rate of each microstructural constituents were evaluated by two ways, one is calculating by an analysis of forward problem that dividing the differential between experimentally measured UTS and 0.2% proof strength (<i>σ</i>₀) by elongation (<i>ε</i>), the other is directly measurement by digital image correlation technique with in-situ tensile test. The UTS of alloys were able to be predicted by simple linear compound law using the UTS of α₂/γ lamellar microstructure and β/γ cellular microstructure, and <i>V</i>_c. And these UTS of each microstructural constituent could also be predicted using their <i>σ</i>₀, <i>ε </i>and work hardening rate. The calculated UTS could reproduce the experimentally measured UTS well, it has a margin of error of only ±5%. By using this method, the volume fraction of the microstructure constituent to meet the required properties that contribute to an input value into the MDM can be output. This work was supported by Council for Science, Technology and Innovation (CSTI), Cross-ministerial Strategic Innovation Promotion Program (SIP), “Material Integration” for revolutionary design system of structural materials.