@misc{WangWangPyczaketal., author = {Wang, Li and Wang, Yihao and Pyczak, Florian and Oehring, Michael and Song, Min and Liu, Yong}, title = {Revealing complex planar defects and their interactions at atomic resolution in a Laves phase containing Co-base superalloy}, series = {Acta Materialia}, volume = {264}, journal = {Acta Materialia}, publisher = {Elsevier BV}, issn = {1359-6454}, doi = {10.1016/j.actamat.2023.119568}, pages = {1 -- 20}, language = {en} } @misc{WangWangLiangetal., author = {Wang, Li and Wang, Yihao and Liang, Xiaopeng and Liu, Bin and He, Junyang and Oehring, Michael and Pyczak, Florian and Liu, Yong}, title = {Revealing the unique evolution and splitting behavior of carbides at atomic-scale in TiAl alloys : the role of elastic interactions and chemical fluctuations}, series = {Acta materialia}, volume = {296}, journal = {Acta materialia}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {1359-6454}, doi = {10.1016/j.actamat.2025.121277}, pages = {1 -- 17}, abstract = {Cubic perovskite-Ti3AlC carbides are essential strengthening particles in TiAl alloys, especially for application above 800 °C where coarsening is expected to occur. However, these carbides can decompose into small sub-particles upon extended annealing, and the underlying atomic-scale mechanisms, especially structural and compositional changes, driving this unique splitting remain unclear. This study revisits this behavior in a Ti-45Al-5Nb-0.75C alloy utilizing probe-corrected transmission electron microscopy, atom probe tomography and first-principle calculations. The results reveal that the elastic interactions significantly influence carbide evolution. While needle-like carbides transform to intact plates during aging, those in high-density regions tend to coalesce or align along elastically softest γ-matrix directions, forming low-energy plate-like carbide conglomerates. With extended annealing, periodic chemical fluctuations driven by lattice misfit, especially along the needles induce splitting. Simultaneously, a γi-phase with a larger tetragonality and a 90°-rotated c-axis relative to the γ matrix emerges between the sub-particles, which exhibits near-zero lattice mismatch with carbides along [001], combined with mass-center shifts of carbides, further stabilizing the split configurations. This study provides atomic-scale insights into the evolution and stability of strengthening precipitates in systems with tetragonal misfit, and offers new strategies for improving creep properties of TiAl alloys by tailoring carbide configurations.}, language = {en} } @misc{LiPyczakOehringetal., author = {Li, Yuzhi and Pyczak, Florian and Oehring, Michael and Wang, Li and Paul, Jonathan and Lorenz, Uwe and Yao, Zekun}, title = {Thermal Stability of gamma' phase in long-term aged Co-Al-W alloys}, series = {Journal of Alloys and Compounds}, volume = {729}, journal = {Journal of Alloys and Compounds}, issn = {0925-8388}, pages = {266 -- 276}, language = {en} } @misc{WangOehringLietal., author = {Wang, Li and Oehring, Michael and Li, Yuzhi and Song, Lin and Liu, Yon and Stark, Andreas and Lorenz, Uwe and Pyczak, Florian}, title = {Microstructure, phase stability and element partitioning of γ/γʹ Co-9Al-9W-2X alloys in different annealing conditions}, series = {Journal of Alloys and Compounds}, volume = {787}, journal = {Journal of Alloys and Compounds}, issn = {0925-8388}, pages = {594 -- 605}, language = {en} } @misc{LiPyczakStarketal., author = {Li, Yuzhi and Pyczak, Florian and Stark, Andreas and Wang, Li and Oehring, Michael and Paul, Jonathan and Lorenz, Uwe}, title = {Temperature dependence of misfit in different Co-Al-W ternary alloys measured by synchrotron X-ray diffraction}, series = {Journal of Alloys and Compounds}, volume = {819}, journal = {Journal of Alloys and Compounds}, issn = {0925-8388}, pages = {9}, 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{WangPyczakZhangetal., author = {Wang, Li and Pyczak, Florian and Zhang, Jian and Lou, Langhong and Singer, Robert F.}, title = {Effect of eutectics on plastic deformation and subsequent recrystallization in the single crystal nickel base superalloy CMSX-4}, series = {Materials Science and Engineering A}, journal = {Materials Science and Engineering A}, number = {532}, issn = {1873-4936}, pages = {487 -- 492}, language = {en} } @misc{GabrischStarkSchimanskyetal., author = {Gabrisch, Heike and Stark, Andreas and Schimansky, Frank-Peter and Wang, Li and Schell, Norbert and Pyczak, Florian}, title = {Carbides in Ti-45Al-5Nb alloys with different carbon contents}, series = {Intermetallics}, journal = {Intermetallics}, number = {33}, issn = {0966-9795}, pages = {44 -- 53}, language = {en} } @misc{WangPyczakZhangetal., author = {Wang, Li and Pyczak, Florian and Zhang, Jian and Singer, Robert F.}, title = {On the role of eutectics during recrystallization in a single crystal nickel-base superalloy - CMSX-4}, series = {International Journal of Materials Research}, volume = {100}, journal = {International Journal of Materials Research}, number = {8}, issn = {2195-8556}, pages = {1046 -- 1051}, language = {en} } @inproceedings{WangPyczakGabrischetal., author = {Wang, Li and Pyczak, Florian and Gabrisch, Heike and Lorenz, Uwe and M{\"u}nch, Mathias and Schimansky, Frank-Peter and Schreyer, Andreas and Stark, Andreas}, title = {Effects of Carbon Content, Annealing Condition and Internal Defects on the nucleation, growth and coarsening of P-type Carbides in High Niobium Containing TiAl Alloys}, series = {Advanced structural and functional intermetallic-based alloys, November 30 - December 5, 2014, Boston, Massachusetts, USA}, booktitle = {Advanced structural and functional intermetallic-based alloys, November 30 - December 5, 2014, Boston, Massachusetts, USA}, publisher = {Curran}, address = {Red Hook, NY}, isbn = {978-1-5108-0634-4}, pages = {61 -- 66}, language = {en} } @misc{WangGabrischLorenzetal., author = {Wang, Li and Gabrisch, Heike and Lorenz, Uwe and Schimansky, Frank-Peter and Schreyer, Andreas and Stark, Andreas and Pyczak, Florian}, title = {Nucleation and thermal stability of carbide precipitates in high Nb containing TiAl alloys}, series = {Intermetallics}, volume = {66}, journal = {Intermetallics}, issn = {0966-9795}, doi = {10.1016/j.intermet.2015.07.001}, pages = {111 -- 119}, language = {en} } @misc{WangLorenzMuenchetal., author = {Wang, Li and Lorenz, Uwe and M{\"u}nch, Mathias and Stark, Andreas and Pyczak, Florian}, title = {Influence of alloy composition and thermal history on carbide precipitation in γ-based TiAl alloys}, series = {Intermetallics}, volume = {89}, journal = {Intermetallics}, issn = {0966-9795}, pages = {32 -- 39}, language = {en} } @misc{WangZenkStarketal., author = {Wang, Li and Zenk, Carolin and Stark, Andreas and Felfer, Peter and Gabrisch, Heike and G{\"o}ken, Mathias and Lorenz, Uwe and Pyczak, Florian}, title = {Morphology evolution of Ti3AlC carbide precipitates in high Nb containing TiAl alloys}, series = {Acta Materialia}, journal = {Acta Materialia}, number = {137}, issn = {1359-6454}, pages = {36 -- 44}, language = {en} } @misc{WangPyczakPauletal., author = {Wang, Li and Pyczak, Florian and Paul, Jonathan and Oehring, Michael and Lorenz, Uwe and Yao, Zekun and Ning, Yongquan}, title = {Rafting of γ′ precipitates in a Co-9Al-9W superalloy during compressive creep}, series = {Materials Science and Engineering}, volume = {719}, journal = {Materials Science and Engineering}, issn = {0921-5093}, doi = {10.1016/j.msea.2018.02.017}, pages = {43 -- 48}, language = {en} } @misc{WangOehringLorenzetal., author = {Wang, Li and Oehring, Michael and Lorenz, Uwe and Stark, Andreas and Pyczak, Florian}, title = {New insights into perovskite-Ti3AlC precipitate splitting in a Ti-45Al-5Nb-0.75C alloy by transmission electron microscopy}, series = {Intermetallics}, volume = {100}, journal = {Intermetallics}, issn = {0966-9795}, doi = {10.1016/j.intermet.2018.06.006}, pages = {70 -- 76}, language = {en} } @misc{WangOehringLorenzetal., author = {Wang, Li and Oehring, Michael and Lorenz, Uwe and Yang, Junjie and Pyczak, Florian}, title = {Influence of alloying additions on L1₂ decomposition in γ-γʹ Co-9Al-9W-2X quaternary alloys}, series = {Scripta Materialia}, volume = {154}, journal = {Scripta Materialia}, issn = {1359-6462}, pages = {176 -- 181}, language = {en} } @misc{SongWangOehringetal., author = {Song, Lin and Wang, Li and Oehring, Michael and Hu, Xingguo and Appel, Fritz and Pyczak, Florian and Zhang, Tiebang}, title = {Evidence for deformation twinning of the D019-α2 phase in a high Nb containing TiAl alloy}, series = {Intermetallics}, volume = {109}, journal = {Intermetallics}, issn = {0966-9795}, doi = {10.1016/j.intermet.2019.03.014}, pages = {91 -- 96}, language = {en} } @misc{WangSongStarketal., author = {Wang, Li and Song, Lin and Stark, Andreas and Liu, Yong and Oehring, Michael and Lorenz, Uwe and Pyczak, Florian}, title = {Identification of Laves phases in a Zr or Hf containing γ-γ′ Co-base superalloy}, series = {Journal of Alloys and Compounds}, volume = {805}, journal = {Journal of Alloys and Compounds}, issn = {0925-8388}, pages = {880 -- 886}, language = {en} } @misc{SongHuWangetal., author = {Song, Lin and Hu, Xingguo and Wang, Li and Stark, Andreas and Lazurenko, Daria V. and Lorenz, Uwe and Lin, Junpin and Pyczak, Florian and Zhang, Tiebang}, title = {Microstructure evolution and enhanced creep property of a high Nb containing TiAl alloy with carbon addition}, series = {Journal of Alloys and Compounds}, volume = {807}, journal = {Journal of Alloys and Compounds}, issn = {0925-8388}, doi = {10.1016/j.jallcom.2019.151649}, pages = {11}, language = {en} } @misc{HanXuWangetal., author = {Han, Liuliu and Xu, Xiandong and Wang, Li and Pyczak, Florian and Zhou, Rui and Liu, Yong}, title = {A eutectic high-entropy alloy with good high-temperature strength-plasticity balance}, series = {Materials Research Letters}, volume = {7}, journal = {Materials Research Letters}, number = {11}, issn = {2166-3831}, pages = {460 -- 466}, language = {en} } @misc{WangOehringLiuetal., author = {Wang, Li and Oehring, Michael and Liu, Yuzhi and Lorenz, Uwe and Pyczak, Florian}, title = {Site occupancy of alloying elements in the L12 structure determined by channeling enhanced microanalysis in γ/γ' Co-9Al-9W-2X alloys}, series = {Acta Materialia}, volume = {162}, journal = {Acta Materialia}, isbn = {1359-6454}, pages = {176 -- 188}, language = {en} } @misc{SongWangZhangetal., author = {Song, Lin and Wang, Li and Zhang, Tiebang and Lin, Junpin and Pyczak, Florian}, title = {Microstructure and phase transformations of omega_o-Ti4Al3Nb based alloys after quenching and subsequent aging at intermediate temperatures}, series = {Journal of Alloys and Compounds}, volume = {821}, journal = {Journal of Alloys and Compounds}, issn = {0925-8388}, pages = {11}, language = {en} } @misc{SongAppelWangetal., author = {Song, Lin and Appel, Fritz and Wang, Li and Oehring, Michael and Hu, Xingguo and Stark, Andreas and He, Junyang and Lorenz, Uwe and Zhang, Tiebang and Lin, Junpin and Pyczak, Florian}, title = {New insights into high-temperature deformation and phase transformation mechanisms of lamellar structures in high Nb-containing TiAl alloys}, series = {Acta Materialia}, volume = {186}, journal = {Acta Materialia}, issn = {1873-2453}, doi = {10.1016/j.actamat.2020.01.021}, pages = {575 -- 586}, language = {en} } @misc{WangKongOehringetal., author = {Wang, Li and Kong, Yi and Oehring, Michael and Song, Min and Pyczak, Florian}, title = {Atomic site occupancy of alloying elements and Laves phase stability in γ-γ′ Co-base superalloys}, series = {Journal of Alloys and Compounds}, volume = {906}, journal = {Journal of Alloys and Compounds}, issn = {1873-4669}, doi = {10.1016/j.jallcom.2022.164261}, abstract = {The atomic site occupancy of alloying elements in the ZrCo2 and HfCo2 based Laves phases formed in the Co-9Al-9W-2Zr and Co-9Al-9W-2Hf alloys was experimentally determined by the combined techniques of energy-dispersive X-ray spectroscopy mapping with atomic resolution and the atom location by channeling enhanced microanalysis (ALCHEMI) method. The results show that both Al and W occupy the Zr site in the C15 and the Hf site in the C36 crystal structure. The atomic locations of Al and W were further confirmed by comparing calculated inelastic cross-sections with experimental ALCHEMI results. Using the determined atomic site occupancies of alloying elements, special quasirandom structure solid solution models with 192 atoms were constructed and employed in first-principles calculations. It is found theoretically that the energy of formation of the C15 structure is always lower than that of the C36 structure at 0 K in both ZrCo2 and HfCo2 phases, no matter whether Al and W are incorporated or not. However, further ab initio molecular dynamics simulations suggest that lattice vibration at finite temperature contributes significantly to the phase stability, stabilizing the C36 structure compared to the C15 type for the (Hf, Al, W)Co2 phase at finite temperature, which fits well with the experimental findings.}, 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{CaoWangTaoetal., author = {Cao, Xianli and Wang, Li and Tao, Hui and He, Weiwei and Liang, Xiaopeng and Liu, Bin and Oehring, Michael and Paul, Jonathan and Pyczak, Florian and Liu, Yong}, title = {Morphology evolution of P-Ti3AlC carbides and their influence on creep properties in a crept Ti-45Al-5Nb-0.75C alloy}, series = {Journal of Materials Research and Technology}, volume = {29}, journal = {Journal of Materials Research and Technology}, publisher = {Elsevier BV}, issn = {2238-7854}, doi = {10.1016/j.jmrt.2024.02.146}, pages = {4181 -- 4190}, language = {en} } @misc{LiuSongPyczaketal., author = {Liu, Xu and Song, Lin and Pyczak, Florian and Stark, Andreas and Wang, Li and Guo, Xiang and Zhang, Tiebang}, title = {Stress-induced orthorhombic O phase in TiAl alloys}, series = {Acta materialia}, volume = {286}, journal = {Acta materialia}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {1359-6454}, doi = {10.1016/j.actamat.2025.120751}, pages = {1 -- 13}, abstract = {The orthorhombic O phase precipitation within the D019-α2 phase has attracted increasing attention recently in high Nb containing TiAl (high Nb-TiAl) alloys since the precipitation temperature is close to the expected service temperature of the alloys. In this study, in-situ synchrotron high energy X-ray diffraction (HEXRD) reveals that the O phase precipitates at 550 °C while it dissolves into the α2 phase at 750 °C during heat treatments. However, under external stress the O phase unexpectedly precipitates from α2 phase at 800 °C and even 900 °C. The O phase formation proceeds further in the presence of a critical stress promoted by internal stress accumulation in the α2 phase, whereas the reverse O→α2 phase transformation takes place when the internal stresses are relaxed. Additionally, it has been revealed that the O phase preferentially precipitates from specifically oriented α2 grains with one of their <110> directions aligned perpendicular and their 〈0001〉 directions rotated by an angle of 120° out of the external load axis. This α2 phase orientation facilitates the α2→O crystal transition during uniaxial compression. Transmission electron microscopy (TEM) study shows that stress-induced α2→O transformation is governed by small atomic shifts in the α2 lattice. In addition, the selective growth of certain O variants via shuffling along an [110]α2 direction is found to accommodate the external strain component in this direction.}, language = {en} }