GAT-2017 (Gamma Alloys Technology - 2017): Other Applications and Materials-Processes Development Efforts
Sponsored by: TMS Structural Materials Division, TMS: Titanium Committee
Program Organizers: Young-Won Kim, Gamteck LLC; Wilfried Smarsly, MTU Aero Engines AG; Junpin Lin, University of Science and Technology Beijing; Pierre Sallot, Safran Tech; Paul Withey, Rolls-Royce; Al Sommer, Del West Engineering, Inc; Rui Yang, Institute of Metal Research CAS; Florian Pyczak, Helmholtz-Zentrum-Geesthacht; Dennis Dimiduk, BlueQuartz Software, LLC

Tuesday 8:30 AM
February 28, 2017
Room: Pacific 17
Location: Marriott Marquis Hotel

Session Chair: Yuyong Chen, Harbin Institute of Technology; Marc Thomas, ONERA

8:30 AM  Invited
IC Engine Valves, an Application for Gamma Ti-Al Alloy Technology: Al Sommer1; 1Del West Engineering, Inc
    Racing venues such as Formula 1 and Moto GP currently use different gamma alloy compositions for intake and exhaust valves. Today’s heavily turbocharged race engines need intake valves where E/ρ is high, consistent with the material’s mechanical strength required for the application < 500˚C. The exhaust valve needs an alloy that has adequate fatigue, creep and corrosion resistance above 800˚C. The E/ρ characteristic of the exhaust valve is nowhere as important in the design of the exhaust valve as it is in the case of the intake. Microstructure and alloy chemistry play a much larger role in the selection of exhaust valve materials for turbo charged race engines than they do in the case of the intake. This work will present both materials test data and race engine performance results to attest to the above claim. An overview of how gamma Ti-Al valves are made will also be presented.

8:55 AM  
CAE-based Analysis of Structural Integrity for an Industrial Gas Turbine Blade Made from TiAl Alloy: Omid Sedaghat1; Siavash Zamani1; Saeed Asadi1; Fatemeh Heydari1; Ali Bakhshi1; 1MAPNA Turbine Blade Eng. & Mfg. Co. - PARTO
    Titanium Aluminide alloys deputes a promising solution for substitution of current Ni-based superalloys with new class of high temperature light weight alloys. In the present study, last stage blade of an industrial gas turbine was selected and service condition was simulated for the TiAl blade. To do so, thermo-physical properties of selected alloy were extracted to find temperature and stress distribution profiles during engine operation using CFD and FEM analyses. In the next step, moreover to vibrational analysis, creep damage mechanism was studied and analyzed to characterize the reliability according to the blade design criteria and comprehensive comparison was made between performances of selected TiAl alloy in contrast with previous Ni-based superalloy. Results show that stresses level could be significantly lowered by using TiAl alloy and advantages would be achieved in damage mechanisms controlling. However design specifications should be reviewed both in turbine side and current TiAl alloys side.

9:15 AM  
O-phase in a Lamellar TiAlNb Alloy Produced by Powder Metallurgy: Heike Gabrisch1; Uwe Lorenz1; Florian Pyczak1; Marcus Rackel1; Andreas Stark1; 1Helmholtz-Zentrum Geesthacht
    High specific strength, high temperature stability and good corrosion resistance make TiAl-alloys attractive candidates for structural applications in aero-engines. Depending on Al-content and alloying elements the alloys are composed of the major phases βo (cubic), α2 (hexagonal) and γ (tetragonal). In the ternary alloy Ti-42Al-8.5Nb (at.-%) improved high temperature strength and better room temperature ductility were attributed to the occurrence of an additional orthorhombic phase (O-phase) that form out of the parent α2 phase during thermal treatment. The O-phase with the ideal composition Ti2AlNb has been reported previously in other ternary alloys Ti-(12-31)Al-(12.5-37)Nb, but not for alloys in the present composition range. In this study the O-phase is identified by single crystal electron diffraction. The morphology of phases within α2 laths of lamellar (α2+γ) colonies is characterized by conventional imaging techniques, HAADF and high resolution imaging.

9:35 AM  
Preparation and Electron Beam Welding of Hot Packed Rolled Powder Metallurgy γ-TiAl Sheets: Zhengguan Lu1; Lei Xu1; Jie Wu1; Ruipeng Guo1; Rui Yang1; 1Institue of Metal Research, CAS
    Atomized powder with a normal composition of Ti-47Al-2Cr-1.8Nb-0.15B (at. %) was used to prepare powder metallurgy (PM) γ-TiAl preforms through hot isostatic pressing. PM method can obtain a more uniform chemical composition and finer microstructure than traditional casting route. Considering the poor room-temperature ductility, hot packed rolling process was studied to prepare PM γ-TiAl sheets and electron beam welding (EBW) of gamma sheets was conducted. Experimental results show that the hot temperature deformation behavior of PM gamma alloy was sensitive to rolling parameters. A set of rolling parameters was optimized to prepare PM gamma sheets with 2.5mm thickness. The microstructure and microhardness of FZ, HAZ and BM is different after welding while no obvious element segregation was observed. The tensile strength of welding joint was also tested, and tensile testing specimens all fracture in the FZ.