Design Approaches and Achievements of Novel Wrought TiAl Alloys for Jet Engine Applications
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.113
Design Approaches and Achievements of Novel Wrought TiAl Alloys for Jet Engine Applications Hideki Wakabayashi, Loris J. Signori, Ali Shaaban, Ryosuke Yamagata, Hirotoyo Nakashima and Masao Takeyama Dept. Materials Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, Meguro-ku, Tokyo, Japan
Abstract
Design approaches and achievements for the development of wrought TiAl alloys to be used for LPT and HPC blades are constructed. In case of Ti-Al-M1-M2 quaternary systems, conventional equivalency concept does not work for the alloy design, and a new thermodynamic database for phase diagram calculations in multi-component systems of the alloys is built by introducing the interaction parameters among four phases of ETi, D2Ti3AlDTi and JTiAl phases in the systems, in order to reproduce the experimentally determined phase diagrams. Based on the phase diagram calculations, the composition range of a unique phase transformation pathway of EDൺDൺEJ in the multi-component system can be identified, and thus model alloys with excellent hot workability even at higher strain rate and mechanical properties can be successfully proposed. It can be concluded that an introduction of bcc E phase and the morphology control through the phase transformation pathway make it possible to improve the room temperature ductility, creep and fatigue crack propagation resistance.
INTRODUCTION Innovation of structural materials is urgently being required for contribution to worldwide issues on energy and environment, and high performance jet engine development with higher thrust-to-weight ratio is one of them, since more than 42,000 new airplanes are to be produced by 2037 [1]. Titanium aluminides based on J-TiAl are one of the materials to be further developed, and a cast TiAl alloy of Ti-48Al-2Nb-2Cr (at.%), so called GE alloy (4822), is currently being applied commercially to low pressure turbine (LPT) blades for GEnxTM engine. Although the possibility of the wrought alloy development using E-Ti phase was originally proposed by our group [2-5],
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MTU recently has developed wrought TiAl alloys TNM (Ti-43.5Al-4Nb-1Mo-0.1B) for being used for LPT blades of PW1100GTM engines, collaborating with University of Leoben headed by H. Clemens [6]. In Japan, a five-year National project of “Structural Materials for Innovation (SM4I)” in Cross-ministerial Strategic Innovation Promotion Program (SIP) was started in 2014 [7], and a challenging R&D activity of innovative structural TiAl alloys aiming at LPT and high-pressure compressor (HPC) blades for jet engines has been placed in this project, where Tokyo Tech is committed to as a technical leader and takes responsibility for the alloy design in collab
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