@misc{TangLiLietal., author = {Tang, Yingchun and Li, Wei and Li, Changle and Lu, Song and Vitos, Levente and Pyczak, Florian}, title = {First-Principles Calculations of Elastic and Thermodynamic Properties for Multi-component Co-based Superalloys}, series = {Metallurgical and materials transactions. A, Physical metallurgy and materials science}, volume = {54 (2023)}, journal = {Metallurgical and materials transactions. A, Physical metallurgy and materials science}, number = {5}, issn = {1543-1940}, doi = {10.1007/s11661-022-06891-z}, pages = {1635 -- 1648}, abstract = {First-principles calculations were performed to investigate the elastic and thermodynamic properties for multi-component Co-based superalloy systems and explored the effect of alloying on stabilizing the γ′ phase. First, the comparisons were carried out for the γ′ phase in Co3(Al,TM) (TM being transition metals) and Ni3Al systems between the present computational results using the EMTO-CPA method and other available DFT calculations as well as experimental data. The lattice parameters, elastic constants, and Debye temperatures are consistent with experimental results and other calculations. The predicted thermodynamic properties, e.g., the Gibbs free energy, excess entropy, and linear thermal expansion coefficient, agree well with CALPHAD results, experimental results, and other available first-principles calculations. A combination of EMTO-CPA method and Debye-Gr{\"u}neisen model is utilized in this work to ensure that the alloying effect on the stability of the γ′ phase in a multi-component Co-based system is captured efficiently. This could open the path for designing novel multi-component Co-based alloys based on first-principles calculation. To demonstrate this, predictions for the properties of multicomponent systems were undertaken. Our results show that Ni aids in the stabilization of the (CoNi)3(Al, Mo, Nb) phase.}, language = {en} } @misc{DistlHauschildtPyczaketal., author = {Distl, Benedikt and Hauschildt, Katja and Pyczak, Florian and Stein, Frank}, title = {Phase Equilibria in the Ti-Rich Part of the Ti-Al-Nb System—Part II: High-Temperature Phase Equilibria Between 1000 and 1300 °C}, series = {Journal of Phase Equilibria and Diffusion}, volume = {43}, journal = {Journal of Phase Equilibria and Diffusion}, number = {5}, issn = {1863-7345}, doi = {10.1007/s11669-022-00999-w}, pages = {554 -- 575}, abstract = {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.}, language = {en} } @misc{LiuSongLiuetal., author = {Liu, Xu and Song, Lin and Liu, Tong and Stark, Andreas and Pyczak, Florian and He, Zhanbing and Lin, Junpin and Zhang, Tiebang}, title = {In- and ex-situ study of the deformation behavior of the βo(ωo) phase in a Ti4Al3Nb alloy during high-temperature compression}, series = {Journal of Alloys and Compounds}, volume = {918}, journal = {Journal of Alloys and Compounds}, issn = {0925-8388}, doi = {10.1016/j.jallcom.2022.165626}, abstract = {In-situ synchrotron-based high energy X-ray diffraction (HEXRD) and ex-situ Gleeble tests were conducted to investigate the deformation behavior of the βo(ωo) phase in a Ti4Al3Nb alloy. In samples compressed at 600 and 800 °C, the brittle ωo phase deforms mostly elastically, resulting in the failure of the Ti4Al3Nb alloy by premature fracture. In a sample deformed at 900 °C, the ωo phase mostly transforms into the βo phase under uniaxial loading. Moreover, the ductility of a Ti4Al3Nb alloy is largely enhanced at this temperature. In a sample deformed at 1000 °C, dynamic recrystallization (DRX) of the βo phase extensively takes place. Direction 1 (D1) and Direction 2 (D2) deviating from the loading direction with an angle of 65° ± 5° and 15° ± 5° are selected to analyze the lattice strain evolution of (110)βo lattice planes. At the late stage of macro strain hardening, deformed[removed]βo//D1 oriented grains bear a higher load due to the occurrence of DRX in[removed]βo//D2 oriented grains. Subsequently, DRX continues in[removed]βo//D1 oriented βo grains. The coordinated deformation of βo grains ensures the good deformability of a Ti4Al3Nb alloy at 1000 °C.}, language = {en} } @misc{LiWangLiangetal., author = {Li, Longjun and Wang, Li and Liang, Zhida and He, Junyang and Qiu, Jingwen and Pyczak, Florian and Song, Min}, title = {Effects of Ni and Cr on the high-temperature oxidation behavior and mechanisms of Co- and CoNi-base superalloys}, series = {Materials and Design}, volume = {224}, journal = {Materials and Design}, issn = {1873-4197}, doi = {10.1016/j.matdes.2022.111291}, abstract = {The high-temperature oxidation behaviors of Co- and CoNi-base alloys with different Ni and Cr additions were investigated by isothermal oxidation in air at 900 and 1000 °C. The structure, composition, and element distribution in the three layers within the oxide scales in different alloys have been explored in detail by electron microscopy, especially with regard to the fine oxide particles in the intermediate layer. Based on the microstructure and phase constitution of the oxide scales, the synergetic effects of alloying elements on the oxidation mechanisms and resistance have been elucidated in detail with the aid of CALPHAD calculation.}, language = {en} } @misc{LiangLilleoddenOvrietal., author = {Liang, Zhida and Lilleodden, Erica and Ovri, Henry and Pyczak, Florian}, title = {Surface Recrystallization in a Co-Based Superalloy During High Temperature Exposure}, series = {Metallurgical and materials transactions. A, Physical metallurgy and materials science}, volume = {53}, journal = {Metallurgical and materials transactions. A, Physical metallurgy and materials science}, number = {12}, issn = {1543-1940}, doi = {10.1007/s11661-022-06852-6}, pages = {4156 -- 4160}, abstract = {The effect of grinding on static recrystallization and oxidation of a novel Co-based superalloy has been studied. The evolution of surface recrystallization after heat treating at 850 °C in air was revealed by comparing ground specimens with electropolished ones. The loss of Al and Ti from the bulk material leads to the formation of a γ′-free region and further promotes recrystallization at the surface.}, language = {en} } @misc{ShangLiuLiangetal., author = {Shang, Yuanyuan and Liu, Shaofei and Liang, Zhida and Pyczak, Florian and Lei, Zhifeng and Heidenreich, Tim and Sch{\"o}ckel, Alexander and Kai, Ji-jung and Gizer, G{\"o}khan and Dornheim, Martin and Klassen, Thomas}, title = {Developing sustainable FeTi alloys for hydrogen storage by recycling}, series = {Communications Materials}, volume = {3}, journal = {Communications Materials}, number = {1}, issn = {2662-4443}, doi = {10.1038/s43246-022-00324-5}, abstract = {Intermetallic alloys such as FeTi have attracted ever-growing attention as a safe and efficient hydrogen storage medium. However, the utilization of high-purity metals for the synthesis of such materials poses considerable concerns over the environmental sustainability of their large-scale production. Here, we report an approach for synthesizing FeTi from industrial scraps of iron (steels C45 and 316 L) and titanium (Ti alloy Grade 2) to reduce the carbon footprint associated with FeTi alloy synthesis, without compromising their hydrogen storage properties. At 50 °C and a pressure of 0 to 100 bar, the alloys obtained by using C45-Ti Grade 2 and 316L-Ti Grade 2 can absorb a maximum amount of hydrogen of 1.61 wt.\% and 1.50 wt.\%, respectively. Moreover, depending on the type of steel utilized, the thermodynamic properties can be modified. Our findings pave a pathway for developing high-performance, environmentally-sustainable FeTi alloys for hydrogen storage purposes using industrial metal wastes.}, language = {en} } @misc{AmherdHidalgoEbelFrykholmetal., author = {Amherd Hidalgo, Alexandra and Ebel, Thomas and Frykholm, Robert and Carre{\~n}o-Morelli, Efra{\´i}n and Pyczak, Florian}, title = {High-oxygen MIM Ti-6Al-7Nb: Microstructure, tensile and fatigue properties}, series = {Materials Today Communication}, volume = {Vol. 34}, journal = {Materials Today Communication}, issn = {2352-4928}, doi = {10.1016/j.mtcomm.2022.104982}, language = {en} } @misc{GabrischJanovskaRackeletal., author = {Gabrisch, Heike and Janovsk{\´a}, Michaela and Rackel, Marcus W. and Pyczak, Florian and Stark, Andreas}, title = {Impact of microstructure on elastic properties in the alloy Ti-42Al-8.5 Nb}, series = {Journal of Alloys and Compounds}, volume = {Vol. 932}, journal = {Journal of Alloys and Compounds}, issn = {1873-4669}, doi = {10.1016/j.jallcom.2022.167578}, language = {en} } @misc{WangLiangLiuetal., author = {Wang, Li and Liang, Xiaopeng and Liu, Bin and Oehring, Michael and Paul, Jonathan David Heaton and Liu, Jie and Song, Min and Pyczak, Florian and Liu, Yong}, title = {Stacking fault formation in perovskite Ti3AlC carbides in a TiAl based alloy during creep at 800°C}, series = {Scripta Materialia}, volume = {Vol. 222}, journal = {Scripta Materialia}, issn = {1872-8456}, doi = {10.1016/j.scriptamat.2022.115034}, language = {en} } @misc{LiuStarkPyczaketal., author = {Liu, Xu and Stark, Andreas and Pyczak, Florian and Zhang, Tiebang}, title = {In-situ synchrotron high energy X-ray diffraction study on the internal strain evolution of D019-α2 phase during high-temperature compression and subsequent annealing in a TiAl alloy}, series = {Journal of Materials Science and Technology}, volume = {Vol. 163}, journal = {Journal of Materials Science and Technology}, issn = {1941-1162}, doi = {10.1016/j.jmst.2023.04.027}, pages = {212 -- 222}, language = {en} } @misc{SongAppelLiuetal., author = {Song, Lin and Appel, Fritz and Liu, Wenhao and Pyczak, Florian and Zhang, Tiebang}, title = {{11¯01} tension twins and {11¯01}-{22¯01}/{22¯01}-{11¯01} double twins in the D019 ordered hexagonal α2-Ti3Al phase}, series = {Acta Materialia}, volume = {260}, journal = {Acta Materialia}, number = {3}, doi = {10.1016/j.actamat.2023.119335}, language = {en} }