一、研究方向

1. 深过冷快速凝固

       深过冷是实现金属材料快速凝固的重要途径。本方向的研究侧重用同步辐射高能X射线衍射和高速摄影等原位表征技术分析纯金属、二元和多元合金快速凝固过程中的亚稳凝固路径、枝晶或共晶生长动力学和强磁场效应，旨在建立描述晶体快速生长的新理论，并认识金属材料在快速凝固条件下的微结构形成机理。

  快速凝固理论研究的代表性成果

  1) D. D. Zhao, J. Gao (2022): "Theory and in situ diagnosis of growth kinetics of dendritic crystals in alloy solidification", Crystal Growth and Design 22, pp.5354-5362.

    2) D. D. Zhao, J. Gao, A. Kao (2020): "Modeling of tip kinetics of undercooled Ti dendrites with consideration of forced flow and oxygen impurity effects", International Journal of Heat and Mass Transfer 159, p.120113.

   3) J. Gao (2018): "A model for free growth of a lamellar eutectic dendrite with an incident flow", Philosophical Transactions of the Royal Society A 376, p.20170209.

    4）J. Gao, A. Kao, V. Bojarevics, K. Pericleous, P. K. Galenko, D. V. Alexandrov (2017): "Modeling of convection, temperature distribution and dendritic growth in glass-fluxed nickel melts", Journal of Crystal Growth 471, pp.66-72.

    5）C. Yang, J. Gao (2015): "Modeling of free eutectic growth and competitive solidification in undercooled near-eutectic alloys based on in-situ measurements", Journal of Materials Science 50, pp.268-278.

  强磁场效应研究的代表性成果

    1）D. D. Zhao, J. Gao (2019): "Liquid phase separation in undercooled Cu–Co alloys under the influence of static magnetic fields", Philosophical Transactions of the Royal Society A 377, p.20180207.

    2) R. J. Zhao, J. Gao, A. Kao, K. Pericleous (2019): "Verification of thermoelectric magnetohydrodynamic flow effects on dendritic tip kinetics by in-situ observations", International Journal of Heat and Mass Transfer 136, pp.1139-1146.

    3）R. J. Zhao, J. Gao, A. Kao, K. Pericleous (2017): "Measurements and modelling of dendritic growth velocities of pure Fe with thermoelectric magnetohydrodynamics convection", Journal of Crystal Growth 475, pp.354-361. 

    4) J. Gao, M. K. Han, A. Kao, K. Pericleous, D. Alexandrov, P. Galenko (2016): "Dendritic growth velocities in an undercooled melt of pure nickel under static magnetic fields: a test of theory with convection", Acta Materialia 103, pp.184-191.

    5）C. Yang, J. Gao (2014): "Dendritic growth kinetics and disorder trapping of the intermetallic compound Ni3Sn under a static magnetic field", Journal of Crystal Growth 394, pp. 24-27.

  同步辐射原位研究的代表性成果

    1）Y. Q. Wang, J. Gao, M. Kolbe, A. Chuang, Y. Ren, D. Matson (2018): "Metastable solidification of hypereutectic Co₂Si–CoSi composition: microstructural studies and in-situ observations", Acta Materialia 142, pp.172-180.

    2）D. D. Zhao, F. Yang, D. Holland-Moritz, M. Kolbe, T. Buslaps, J. Gao (2021): "In situ studies of liquid-liquid phase separation, solidification sequence and dendrite growth kinetics in electrostatically levitated Ti–Y alloys", Acta Materialia 213, p.116962.

    3）R. J. Zhao, Y. Q. Wang, J. Gao, E. Baker, D. M. Matson, M. Kolbe, A. Chuang, Y. Ren (2020): "In situ and ex situ studies of anomalous eutectic formation in undercooled Ni–Sn alloys", Acta Materialia 197, pp.198-211.

    4）R. J. Zhao, T. T. Yang, Y. Q. Wang, Y. Ren, J. Gao (2021): "In situ X-ray diffraction and HAADF-STEM study of disorder trapping in intermetallic Ni₃Sn compound", Scripta Materialia 193, pp.55-58.

    5）Y. Q. Wang, J. Gao, W. H. Sun, A. Shahani (2022): "In situ observation of faceted growth and morphological instability of a complex-regular eutectic in Zn–Mg–Al system", Scripta Materialia 206, p.114224.

  非平衡凝固组织研究的代表性成果

    1)  Y. K. Zhang, J. Gao, M. Kolbe, S. Klein, C. Yang, H. Yasuda, D. M. Herlach, Ch.-A. Gandin (2013): "Phase selection and microstructure formation in undercooled Co–61.8at.%Si melts under various containerless processing conditions", Acta Materialia 61, pp.4861-4873.

   2）C. Yang, J. Gao, Y. K. Zhang, M. Kolbe, D. M. Herlach (2011): "New evidence for dual origin of anomalous eutectic structures in undercooled Ni–Sn alloys: in-situ observations and EBSD characterization", Acta Materialia 59, pp.3915-3926.

   3) Y. K. Zhang, J. Gao, D. Nagamatsu, T. Fukuda, H. Yasuda, M. Kolbe, J. C. He (2008): "Reduced droplet coarsening in electromagnetically levitated and phase-separated Cu–Co alloys by imposition of a static magnetic field", Scripta Materialia 59, pp.1002-1005.

    4）Y. Q. Wang, C. Paul, S. Moniri, J. Gao, T. Volkenandt, V. De Andrade, A. J. Shahani (2020): "Integrated three-dimensional characterization of reactive phase formation and coarsening during isothermal annealing of metastable Zn–3Mg–4Al eutectic", Materials Characterization 170, p.110685.

    5) Y. Q. Wang, J. Gao, Y. Ren, V. De Andrade, A. J. Shahani (2020): "Formation of a three-phase spiral structure due to competitive growth of a peritectic phase with a metastable eutectic", JOM 72, pp.2965-2973.

2. 磁驱动相变材料

        磁驱动相变是指金属、氧化物和碳化物等磁性材料在施加外磁场后出现的结构或磁性相变。本方向的研究侧重采用同步辐射、中子和高分辨透射电镜等先进表征技术理解与磁驱动相变关联的磁弹性、磁热效应以及多铁耦合（铁磁与铁电、铁弹有序的叠加与关联）现象。

    磁驱动相变材料的代表性成果

    1) D. Huang, T. Y. Ma, D. E. Brown, S. H. Lapidus, Y. Ren, J. Gao (2021): "Nanoscale phase separation and large refrigerant capacity in magnetocaloric material LaFe_11.5Si_1.5", Chemistry of Materials 33, pp.2837-2846.

    2) R. H. Kou, Z. W. Chen, S. Ouyang, J. Gao (2020): "Phase separation-induced nanoscale heterogeneity in Gd₅Si_1.5Ge_2.5", Acta Materialia 197, pp.163-171.

    3) D. Huang, J. Gao, S. H. Lapidus, D. E. Brown, Y. Ren (2020): "Exotic hysteresis of ferrimagnetic transition in Laves compound TbCo₂", Materials Research Letters 8, pp.97-102.

    4) R. H. Kou, J. Gao, Z. H. Nie, Y. D. Wang, D. E. Brown, Y. Ren (2020): "Magnetic transitions and magnetocaloric effect of Gd₄Nd₁Si₂Ge₂", Journal of Alloys and Compounds 826, p.154117.

    5) R. H. Kou, J. Gao, Z. H. Nie, Y. D. Wang, D. E. Brown, Y. Ren (2019):"Evidence for a short-range chemical order of Ge atoms and its critical role in inducing a giant magnetocaloric effect in Gd₅Si_1.5Ge_2.5", Journal of Alloys and Compounds 808, p.151751.

3. 金属增材制造

        金属增材制造中熔池的凝固是一个典型的非平衡凝固过程。本方向的研究侧重对不锈钢、形状记忆合金、高温合金和钛合金等在激光和电子束增材制造过程中的非平衡凝固效应进行识别和调控。

  金属增材制造研究的代表性成果

    1）R. J. Zhao, T. T. Yang, H. L. Liao, N. Fenineche, C. Coddet, J. Gao (2021): "Nanoscale chemistry and atomic-scale microstructure of a bulk Ni₃Sn material built using selective laser melting of elemental powder blends", Materials & Design 211, p.110152.  

     2) R. J. Zhao, J. Gao, H. L. Liao, N. Fenineche, C. Coddet (2020): "Selective laser melting of elemental powder blends for fabrication of homogeneous bulk material of near-eutectic Ni‒Sn composition", Additive Manufacturing 34, p.101261.

4. 高温合金

       高温合金是制造飞机发动机和燃汽轮机叶片的重要材料，是典型的多组元合金。本方向的研究侧重采用中子、同步辐射等大科学装置手段原位揭示镍基单晶高温合金在定向凝固过程中的偏析、取向偏离等缺陷的形成机理。 

    高温合金研究的代表性成果

1) Y. H. Wang, D. D. Zhao, J. Gao, L. H. He (2024): "Disorder trapping and recrystallization-induced grain refinement in undercooled Ni₃Ga melts", Scripta Materialia 252, p.116275.

2) Y. H. Wang, J. Gao, L. H. He (2024): "Facile formation of a superalloy-like microstructure in Ni₇₇Ga₂₃ alloys by rapid solidification processing", Scripta Materialia 239, p.115822.

3) 高建荣，王彦惠，石桐，李树贤（2024）：单晶高温合金定向凝固过程的中子原位诊断系统及方法，中国发明专利，CN118425208A（已授权）。

二、科研项目  

1. 国家自然科学基金中德合作研究重点项目（2021－2023）：

         深过冷镍基高温合金非平衡凝固过程的原位观测研究

2.  国家自然科学基金重点项目子课题（2019－2023）：

        基于晶体长/短程序和磁性团簇拓扑关联及外场调控的新型磁驱相变材料研究

3. 国家重点研发计划项目子课题（2022－2026)：

        单晶高温合金凝固过程的中子原位研究装置与技术