@misc{KolbWheelerMathuretal., author = {Kolb, M. and Wheeler, Jeffrey M. and Mathur, H. N. and Neumeier, Steffen and Korte-Kerzel, Sandra and Pyczak, Florian and Michler, Johann and G{\"o}ken, Mathias}, title = {Local mechanical properties of the (β0+ω0) composite in multiphase titanium aluminides studied with nanoindentation at room and high temperatures}, series = {Materials Science and Engineering A}, volume = {665}, journal = {Materials Science and Engineering A}, issn = {0921-5093}, doi = {10.1016/j.msea.2016.04.026}, pages = {135 -- 140}, language = {en} } @misc{NeumeierFreundBezoldetal., author = {Neumeier, S. and Freund, L. P. and Bezold, A. and K{\"o}brich, M. and Vollh{\"u}ter, J. and Hausmann, D. and Solis, C. and Stark, A. and Schell, N. and Pyczak, F. and Felfer, P. and Gilles, R. and G{\"o}ken, M.}, title = {Advanced Polycrystalline γ′-Strengthened CoNiCr-Based Superalloys}, series = {Metallurgical and Materials Transactions A}, volume = {55}, journal = {Metallurgical and Materials Transactions A}, number = {5}, publisher = {Springer Science and Business Media LLC}, issn = {1073-5623}, doi = {10.1007/s11661-024-07319-6}, pages = {1319 -- 1337}, abstract = {AbstractNovel compositionally complex CoNiCr-based superalloys with excellent mechanical properties have been developed, which combine the multiprincipal element nature of high-entropy alloys with the precipitation strengthening in superalloys. A series of advanced polycrystalline γ′-strengthened CoNiCr-based superalloys, called CoWAlloys, with varying contents of Al, W, Ti, Ta, Mo, and Nb are investigated in terms of microstructure, thermophysical properties, yield, and creep strength. The microstructure of all CoWAlloys consists of an fcc solid solution matrix phase (approximate γ composition in at. pct: 50Co-20Ni-20Cr-10X (X = other alloying elements)), which is strengthened by a multicomponent γ′ (Ni,Co)3(Al,Ti,Ta,W,Nb)-based precipitate phase with a very high-volume fraction of around 60 vol pct (approximate γ′ composition in at. pct: 45Ni-30Co-25X). These alloys have high solidus temperatures above 1300 °C and moderate γ′ solvus temperature between 985 °C and 1080 °C leading to a large processing window. The increasing content of γ′-forming elements Ti, Ta, W, and Nb decreases this window, but increases the γ/γ′ lattice misfit and the anti-phase boundary energy, which contribute to a significantly higher yield and creep strength. Their properties are discussed in comparison with conventional polycrystalline Ni-base superalloys and so-called L12-strengthened high-entropy alloys, revealing that the creep strengths of the CoWAlloys are significantly higher. This is due to the reduced strain rate sensitivity of the CoWAlloys due to different underlying deformation mechanisms: By increasing the anti-phase boundary energy, a transition to stacking fault shearing and microtwinning occurs, which leads to the enhanced creep strength. Based on these results, guidelines and strategies for the design of next-generation advanced high-temperature polycrystalline superalloys are proposed. Graphical Abstract}, language = {en} } @misc{HaussmannBreslerNeumeieretal., author = {Haußmann, L. and Bresler, J. and Neumeier, S. and Pyczak, F. and G{\"o}ken, M.}, title = {Interdiffusion Coefficients and Strengthening Effects of Nb, Ta, and Zr in the α2-Ti3Al Phase}, series = {Journal of Phase Equilibria and Diffusion}, volume = {45 (2024)}, journal = {Journal of Phase Equilibria and Diffusion}, number = {4}, publisher = {Springer Science and Business Media LLC}, issn = {1547-7037}, doi = {10.1007/s11669-024-01105-y}, pages = {764 -- 771}, abstract = {AbstractThe creep properties of fully lamellar γ/α2 titanium aluminides can be significantly improved by alloying with Nb, Ta or Zr. While the influence of these alloying elements on the γ-phase has already been examined, their diffusivity and strengthening properties in the α2-phase are still lacking. In order to study the effect of Nb, Ta and Zr in α2-Ti3Al, the alloys Ti-33Al, Ti-33Al-5Nb, Ti-33Al-5Ta and Ti-33Al-5Zr were investigated using a diffusion couple approach and strain rate jump tests. The results show that Zr diffuses the fastest, followed by Nb and Ta. Furthermore, these alloying elements also increase the strength compared to a binary Ti-33Al alloy, from which Zr leads to the highest strength increase followed by Ta and Nb. The lower diffusivity of Ta becomes increasingly important at higher temperatures and lower strain rates resulting in a higher strengthening potential than Nb and Zr under such conditions.}, language = {en} }