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赵广迪,臧喜民,赵卓.镍基高温合金U720Li的熔化和凝固过程原位观察[J].稀有金属材料与工程(英文),2020,49(11):3809~3815.[Zhao Guangdi,Zang Ximin and Zhao Zhuo.In-Situ observations of melting and solidification processes of Ni-based superalloy U720Li[J].Rare Metal Materials and Engineering,2020,49(11):3809~3815.]
In-Situ observations of melting and solidification processes of Ni-based superalloy U720Li
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Received:March 06, 2020  Revised:April 16, 2020
Key words: Ni-based superalloy  Melting  Solidification  High temperature confocal laser scanning microscopy  In-situ observation
Foundation item:国家自然科学基金资助(项目号51904146,U1960203),辽宁省博士科研启动(项目号2019-BS-125)
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Zhao Guangdi,Zang Ximin and Zhao Zhuo  
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      The melting and solidification behaviors of Ni-based superalloy U720Li were investigated by means of high temperature confocal laser scanning microscopy (HT-CLSM) and differential thermal analysis (DTA) in this study. The in-situ HT-CLSM observation of melting process shows that incipient melting takes place at the front of some eutectic (γ + γ′) particles at about 1122 ℃. But the molten pools cannot expand rapidly until the temperature is increased above 1173 ℃. Discrete spotted molten pools occurs on localized region of the dendrite area at around 1195 ℃, and the radius of these molten pools increases slowly with raising temperature. The eutectic (γ + γ′) particles precipitated in the interdendritic region begin to melt at about 1235 ℃ and the molten pools rapidly expand towards the dendrite area as the temperature increases. Finally, the dendrites are completely melted at 1333 ℃. The in-situ HT-CLSM observation of solidification process shows that the melt starts to solidify at about 1315 ℃ and the solidification ends at around 1180 ℃. As the temperature decreases the transformation rate of the solid phase initially increases slowly and then increases rapidly until a maximum value, afterwards it quickly decreases and at the final solidification stage it is about zero. The DTA analysis indicates that the onset temperature of γ′ dissolution in the ingot is about 1047 ℃, and the ingot is completely melted at 1362 ℃. By comparison, it is clear that the results of HT-CLSM in-situ observations are about 30 ℃ lower than those of DTA analysis.