@misc{GuptaPaulSchmittetal., author = {Gupta, Vipul and Paul, Jonathan David Heaton and Schmitt, Ingo and Pyczak, Florian}, title = {SciLitMiner : an intelligent system for scientific literature mining and knowledge discovery}, series = {Advanced intelligent systems}, journal = {Advanced intelligent systems}, publisher = {Wiley}, address = {Weinheim}, issn = {2640-4567}, doi = {10.1002/aisy.202501235}, pages = {1 -- 20}, abstract = {Recent advances in data mining have enabled automation in literature-based discovery (LBD), allowing synergistic evaluation of experimental findings reported in scientific publications. However, existing tools and digital libraries fall short in generating relevant literature collections and evaluating them for highly specific questions. This article presents SciLitMiner, an intelligent system to address this gap. SciLitMiner enables federated ingestion of literature from digital libraries; applies advanced retrieval techniques, including dataset-aware retrieval from visual elements, to identify relevant studies; and leverages retrieval-augmented generation (RAG) tailored to domain-specific knowledge reasoning. The system is applied in materials science to study the creep behavior of γ-TiAl alloys, revealing the intricate interplay between material, process, microstructure, and creep rate, represented through knowledge graphs. Two domain experts rate responses from the knowledge reasoning workflow with OpenAI large language models (LLMs) as the backbone above "good" (3 on a 5-point Likert scale) in over 90\% across qualitative criteria, indicating strong performance. In a case study, the workflow also outperforms gpt-4.5-turbo with web search and other leading tools in reliability. A second case study benchmarks open-source LLMs as drop-in replacements for proprietary models, demonstrating comparable-to-superior performance. The system's flexibility enables its use in automated LBD across diverse research domains.}, 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} } @misc{StarkRackelPyczak, author = {Stark, Andreas and Rackel, Marcus W. and Pyczak, Florian}, title = {How rapid heating and quenching cycles affect phase evolution in advanced γ-TiAl alloys : an in situ synchrotron radiation study}, series = {MRS communications}, volume = {15}, journal = {MRS communications}, number = {4}, publisher = {Springer Science and Business Media LLC}, address = {Berlin}, issn = {2159-6867}, doi = {10.1557/s43579-025-00756-3}, pages = {790 -- 795}, abstract = {Additive manufacturing (AM) processes are increasingly considered as an alternative manufacturing route to produce complex aircraft components out of γ-TiAl-based alloys. Due to the process-related high and short-time energy input, extremely fast heating and cooling rates occur which can result in thermodynamic and chemical disequilibrium. We studied the effect of rapid heating and quenching cycles in a Ti-48Al-2Nb-2Cr (in at.\%) alloy by carrying out in situ high-energy X-ray diffraction experiments in which AM-related heating cycles were simulated. These in situ experiments allow to determine the influence of cooling rate and a chosen powder bed temperature on phase evolution.}, language = {en} } @misc{StarkLottPyczak, author = {Stark, Andreas and Lott, Dieter and Pyczak, Florian}, title = {A dilatometer and in situ synchrotron X-ray diffraction study : α-quenching and reheating of a Nb-rich titanium aluminide alloy}, series = {MRS advances}, volume = {10}, journal = {MRS advances}, number = {14}, publisher = {Springer Science and Business Media LLC}, address = {Cham}, issn = {2731-5894}, doi = {10.1557/s43580-025-01382-w}, pages = {1767 -- 1772}, abstract = {Intermetallic γ-TiAl-based alloys are currently used as structural materials for turbine blades in aero engines. Additive manufacturing is increasingly considered as an additional manufacturing route for components consisting of γ titanium aluminides; however, the high heating and cooling rates result in chemical and thermodynamical disequilibrated microstructures. In our study, in situ synchrotron X-ray diffraction was applied to follow the formation of the disequilibrium microstructure during quenching and to study its re-equilibration during a subsequent annealing treatment in a Nb-rich γ-TiAl-based alloy. The quenched sample showed an incomplete massive transformation, with large remaining α2 grains. During reheating, the analysis of the collected data showed that equilibration of the quenched microstructure takes place in several reordering and transformation steps, e.g., orthorhombic distortion of the hexagonal α2 phase (around 550 °C), almost complete transformation of the supersaturated quenched α2 to γ (around 850 °C), and retransformation of γ to new α2 (around 1050 °C).}, language = {en} } @misc{LiuLiuWuetal., author = {Liu, Shen and Liu, Xu and Wu, Qiaohan and Li, Yixuan and Shi, Qiuyi and Song, Lin and Pyczak, Florian and Stark, Andreas and Li, Xiaobing and Zhang, Tiebang}, title = {In-situ synchrotron high energy X-ray diffraction study on the internal strain evolution of an extruded Ti-45Al-8Nb-0.2C alloy during high-temperature compression}, series = {Materials characterization}, volume = {230}, journal = {Materials characterization}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {1044-5803}, doi = {10.1016/j.matchar.2025.115746}, pages = {1 -- 12}, abstract = {Due to their exceptional properties, γ-TiAl based alloys present substantial prospect for aerospace and automotive applications. However, the significant disparity in plasticity between the D019-α2 and L10-γ phases greatly affects TiAl alloys' service behavior. This study investigates the internal strain accumulation in the α2 and γ phases of an extruded Ti-45Al-8Nb-0.2C alloy during compression at 900 °C and the subsequent stress relaxation behavior during annealing at 850 °C, using in situ synchrotron high-energy X-ray diffraction (HEXRD). During compression, the γ phase starts to yield plastically at approximately 410 MPa true stress, progressively shifting the load to the α2 phase and generating high residual stress in the α2 phase after deformation. However, annealing at 850 °C for 30 min only partially relieves the residual stress in the α2 phase, with the relaxation rate decreasing substantially after the first 10 min. Furthermore, when the true stress reaches 790 MPa during compression, the α2 phase undergoes rigid-body rotation to accommodate the plastic deformation of the adjacent γ phase, initiating texture evolution that ultimately forms a distinct fiber texture.}, 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{LiuSongStarketal., author = {Liu, Xu and Song, Lin and Stark, Andreas and Pyczak, Florian and Zhang, Tiebang}, title = {In-situ synchrotron high energy X-ray diffraction study on the deformation mechanisms of D019-α2 phase during high-temperature compression in a TiAl alloy}, series = {Journal of Materials Research and Technology}, volume = {33}, journal = {Journal of Materials Research and Technology}, publisher = {Elsevier BV}, issn = {2238-7854}, doi = {10.1016/j.jmrt.2024.10.231}, pages = {5850 -- 5862}, 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} } @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{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} }