@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{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{LiuSongStarketal., author = {Liu, Xu and Song, Lin and Stark, Andreas and Lorenz, Uwe and He, Zhanbing and Lin, Junpin and Pyczak, Florian and Zhang, Tiebang}, title = {Deformation and phase transformation behaviors of a high Nb-containing TiAl alloy compressed at intermediate temperatures}, series = {Journal of Materials Science and Technology}, volume = {102}, journal = {Journal of Materials Science and Technology}, issn = {0861-9786}, doi = {10.1016/j.jmst.2021.06.041}, pages = {89 -- 96}, abstract = {In modern β-solidified TiAl alloys, the decomposition of α2 phase is frequently observed during heat treatment or high-temperature deformation of the alloys. In this study, high-temperature deformation and decomposition mechanisms of α2 phase in a Ti-45Al-8.5Nb-0.2B-0.2W-0.02Y alloy are investigated. In a sample deformed at 800 °C, the precipitation of βo(ωo) phase is observed within the equiaxed α2 phase. The nucleation of ωo particles within the βo matrix indicates the α2→βo→ωo transformation. In addition, numerous γ phase precipitates form within the βo(ω) areas. The α2 lamellae decompose into ultrafine (α2+γ) lamellae and coarsened γ lamellae via α2→α2+γ and α2→γ transformation, respectively. Moreover, the ωo phase nucleates within the ultrafine lamellae via α2→ωo transformation. However, in a sample deformed at 1000 °C, the nucleation of βo particles is sluggish, which is caused by the efficient release of the internal stress via dynamic recrystallization (DRX). These results indicate that complex phase transformations can be introduced by the decomposition of α2 phase in TiAl alloys with a high amount of β-stabilizing elements.}, language = {en} } @misc{SongAppelPyczaketal., author = {Song, Lin and Appel, Fritz and Pyczak, Florian and Zhanbing, He and Junpin, Lin and Tiebang, Zhang}, title = {Characterization of primary, secondary and tertiary {202¯1}<1¯014> successive internal twins in the D019 ordered hexagonal α2-Ti3Al phase}, series = {Acta Materialia}, journal = {Acta Materialia}, number = {222}, issn = {1873-2453}, doi = {10.1016/j.actamat.2021.117391}, abstract = {Due to the lack of independent slip systems and the difficulty in mechanical twinning, D019 ordered α2-Ti3Al phase is known to be of substantial mechanical anisotropy, which partly accounts for the low ductility of two-phase (α2+γ) TiAl alloys. However, recent studies have shown that in Al-rich α2 phase compression deformation twins can be activated, which could be beneficial for the ductility of the alloys. In the present study, for the first time, we have revealed a novel internal twinning mechanism of α2 phase in a TiAl alloy deformed at high temperature. Three twin generations of a common type {202¯1}[removed] were revealed: Secondary twins formed within the primary twin, and tertiary twins formed in the secondary twin. It is important to note that this internal twin structure can only be observed in the [removed] direction but not the commonly used [removed] direction. The shear plane P of all twin variants is of type {12¯10}. Due to the variation of the twinning elements between the twin variants, the twinning shear is blunted. The interfaces between the twin variants are characterized by high-resolution electron microscopy. Special attention was paid to the structure of the coherent and incoherent twin boundaries. The effect of chemical ordering is discussed. Our results also shed light on the complex twinning mechanisms in hexagonal structures.}, 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{LinZhuangWongetal., author = {Lin, Der-Song and Zhuang, Xuefeng and Wong, Serena H. and Kupnik, Mario and Khuri-Yakub, Butrus T.}, title = {Encapsulation of Capacitive Micromachined Ultrasonic Transducers Using Viscoelastic Polymer}, series = {Journal of Microelectromechanical Systems}, volume = {19}, journal = {Journal of Microelectromechanical Systems}, number = {6}, issn = {1941-0158}, doi = {10.1109/JMEMS.2010.2076786}, pages = {1341 -- 1351}, language = {en} } @inproceedings{LinZhuangWodnickietal., author = {Lin, Der-Song and Zhuang, Xuefeng and Wodnicki, Robert and Woychik, Charles. G. and Oralkan, {\"O}mer and Kupnik, Mario and Khuri-Yakub, Butrus T.}, title = {Packaging of large and low-pitch size 2D ultrasonic transducer arrays}, series = {IEEE 23rd International Conference on Micro Electro Mechanical Systems (MEMS), 2010}, booktitle = {IEEE 23rd International Conference on Micro Electro Mechanical Systems (MEMS), 2010}, publisher = {IEEE}, address = {Piscataway, NJ}, isbn = {978-1-424-45761-8}, pages = {508 -- 511}, 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{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{LazurenkoLaptevGolkovskyetal., author = {Lazurenko, Daria V. and Laptev, Ilia S. and Golkovsky, Mikhail G. and Stark, Andreas and Paul, Jonathan and Bataev, Ivan A. and Ruktuev, Alexey A. and Song, Lin and Gollwitzer, Christian and Pyczak, Florian}, title = {Influence of the Ti/Al/Nb ratio on the structure and properties on intermetallic layers obtained on titanium by non-vacuum electron beam cladding}, series = {Materials Characterization}, volume = {163}, journal = {Materials Characterization}, issn = {1044-5803}, pages = {13}, 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} } @misc{GuoSongLiuetal., author = {Guo, Xiang and Song, Lin and Liu, Xu and Stark, Andreas and Pyczak, Florian and Zhang, Tiebang}, title = {In-situ synchrotron HEXRD study on the phase transformation mechanisms of the ω-related phases in a Ti4Al3Nb alloy}, series = {Materials Characterization}, volume = {Vol. 200}, journal = {Materials Characterization}, issn = {1873-4189}, doi = {10.1016/j.matchar.2023.112901}, 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{BertoHuaParketal., author = {Berto, Federico and Hua, Chuanbo and Park, Junyoung and Luttmann, Laurin and Ma, Yining and Bu, Fanchen and Wang, Jiarui and Ye, Haoran and Kim, Minsu and Choi, Sanghyeok and Zepeda, Nayeli Gast and Hottung, Andr{\´e} and Zhou, Jianan and Bi, Jieyi and Hu, Yu and Liu, Fei and Kim, Hyeonah and Son, Jiwoo and Kim, Haeyeon and Angioni, Davide and Kool, Wouter and Cao, Zhiguang and Zhang, Qingfu and Kim, Joungho and Zhang, Jie and Shin, Kijung and Wu, Cathy and Ahn, Sungsoo and Song, Guojie and Kwon, Changhyun and Tierney, Kevin and Xie, Lin and Park, Jinkyoo}, title = {RL4CO : an extensive reinforcement learning for combinatorial optimization benchmark}, series = {KDD '25 : proceedings of the 31st ACM SIGKDD Conference on Knowledge Discovery and Data Mining V.2}, journal = {KDD '25 : proceedings of the 31st ACM SIGKDD Conference on Knowledge Discovery and Data Mining V.2}, publisher = {ACM}, address = {New York, NY, USA}, isbn = {979-8-4007-1454-2}, doi = {10.1145/3711896.3737433}, pages = {5278 -- 5289}, abstract = {Combinatorial optimization (CO) is fundamental to several real-world applications, from logistics and scheduling to hardware design and resource allocation. Deep reinforcement learning (RL) has recently shown significant benefits in solving CO problems, reducing reliance on domain expertise and improving computational efficiency. However, the absence of a unified benchmarking framework leads to inconsistent evaluations, limits reproducibility, and increases engineering overhead, raising barriers to adoption for new researchers. To address these challenges, we introduce RL4CO, a unified and extensive benchmark with in-depth library coverage of 27 CO problem environments and 23 state-of-the-art baselines. Built on efficient software libraries and best practices in implementation, RL4CO features modularized implementation and flexible configurations of diverse environments, policy architectures, RL algorithms, and utilities with extensive documentation. RL4CO helps researchers build on existing successes while exploring and developing their own designs, facilitating the entire research process by decoupling science from heavy engineering. We finally provide extensive benchmark studies to inspire new insights and future work. RL4CO has already attracted numerous researchers in the community and is open-sourced at https://github.com/ai4co/rl4co.}, 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{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} }