TY - CHAP A1 - Hauschildt, Katja A1 - Stark, Andreas A1 - Lorenz, Uwe A1 - Schell, Norbert A1 - Fischer, Torben A1 - Blankenburg, Malte A1 - Müller, Martin A1 - Pyczak, Florian T1 - Diffusion brazing of γ-TiAl-alloys: Investigations of the joint by electron microscopy and high-energy X-ray diffraction T2 - Intermetallic-based alloys - science, technology and applications, symposium held November 25-30, Boston, Massachusetts, U.S.A Y1 - 2013 U6 - https://doi.org/10.1557/opl.2012.1750 SP - 215 EP - 220 PB - Cambridge Univ. Press CY - Cambridge ER - TY - GEN A1 - Distl, Benedikt A1 - Hauschildt, Katja A1 - Rashkova, Boryana A1 - Pyczak, Florian A1 - Stein, Frank T1 - Phase Equilibria in the Ti-Rich Part of the Ti-Al-Nb System—Part I: Low-Temperature Phase Equilibria Between 700 and 900 °C T2 - Journal of Phase Equilibria and Diffusion N2 - Precise knowledge of the phase equilibria in the Ti-Al-Nb system between 700 and 900 °C is of crucial importance for the urgently needed improvement of TiAl-based turbine materials already in industrial use to achieve further energy savings. As a result of the occurrence of the two ternary intermetallic phases ωo (“Ti4NbAl3”) and O (“Ti2NbAl”), which form in the solid state just in the range of the application-relevant temperatures, the phase relations are very complex and not well studied. In the present investigation, isothermal sections of the Ti-rich part of the Ti-Al-Nb system at 700, 800, and 900 °C were determined by a systematic study of 15 ternary alloys, one solid-solid diffusion couple, and three liquid-solid diffusion couples. Using scanning electron microscopy, electron probe microanalysis (EPMA), x-ray diffraction (XRD), high-energy XRD (HEXRD), differential thermal analysis (DTA), and transmission electron microscopy (TEM) investigations, type and composition of phases as well as phase transitions were determined. With these results, the phase equilibria were established. A focus of the investigations is on the homogeneity ranges of the two ternary phases ωo and O, which both are stable up to temperatures above 900 °C. Based on the compositions measured for the ωo phase and its crystal structure type, a new formula (Ti,Nb)2Al is suggested. The results also indicate that the phase field of the ωo phase is split into two parts at 900 °C because of the growing phase field of the ordered (βTi,Nb)o phase. Y1 - 2022 U6 - https://doi.org/10.1007/s11669-022-00963-8 SN - 1863-7345 VL - 43 IS - 3 SP - 355 EP - 381 ER - TY - GEN A1 - Distl, Benedikt A1 - Hauschildt, Katja A1 - Pyczak, Florian A1 - Stein, Frank T1 - Phase Equilibria in the Ti-Rich Part of the Ti-Al-Nb System—Part II: High-Temperature Phase Equilibria Between 1000 and 1300 °C T2 - Journal of Phase Equilibria and Diffusion N2 - The knowledge of phase equilibria in the Ti-Al-Nb system above 1000 °C is of importance for the manufacturing of TiAl-based parts for high-temperature structural applications. Especially the extended homogeneity range of the cubic (βTi,Nb) phase, which is determined by its Al solubility, and the position and extension of the high-temperature (αTi) phase is of crucial importance for the hot-workability and microstructure control of these alloys. However, the phase diagrams reported in the literature are very contradicting especially regarding these aspects. For this reason, a systematic reinvestigation of the phase equilibria in this part of the system was carried out. A total of 17 ternary alloys were synthesized, heat-treated at 1000-1300 °C, and analyzed by electron probe microanalysis (EPMA), x-ray diffraction (XRD), high-energy XRD (HEXRD), and differential thermal analysis (DTA) to determine composition and type of equilibrium phases as well as transition temperatures. With this information, isothermal sections of the Ti-rich part of the Ti-Al-Nb system at 1000, 1100, 1200, and 1300 °C were established. An isolated (βTi,Nb)o phase field is found to be stable at 1000 and 1100 °C. Furthermore, the formation and homogeneity range of (αTi) at high temperatures as well as the presence of Ti3Al at 1200 °C is experimentally investigated and discussed. Based on the observed phase equilibria and transition temperatures, an improved reaction scheme for the entire Ti-Al-Nb system is proposed. Y1 - 2022 U6 - https://doi.org/10.1007/s11669-022-00999-w SN - 1863-7345 VL - 43 IS - 5 SP - 554 EP - 575 ER - TY - GEN A1 - Hauschildt, Katja A1 - Stark, Andreas A1 - Schell, Norbert A1 - Müller, Martin A1 - Pyczak, Florian T1 - The transient liquid phase bonding process of a γ-TiAl alloy with brazing solders containing Fe or Ni T2 - Intermetallics Y1 - 2019 SN - 0966-9795 VL - 106 SP - 48 EP - 58 ER -