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Effect of High Magnetic Field on the Microstructure in Directionally Solidified Co-Al-W Alloy |
Jianbo YU1(), Yuan HOU1, Chao ZHANG2, Zhibin YANG2, Jiang WANG1, Zhongming REN1 |
1 State Key Laboratory of Advanced Special Steel & Shanghai Key Laboratory of Advanced Ferrometallurgy, Shanghai University, Shanghai 200072, China 2 School of Metallurgical and Materials Engineering, Zhangjiagang Campus of Jiangsu University of Science and Technology, Zhangjiagang 215600, China |
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Cite this article:
Jianbo YU, Yuan HOU, Chao ZHANG, Zhibin YANG, Jiang WANG, Zhongming REN. Effect of High Magnetic Field on the Microstructure in Directionally Solidified Co-Al-W Alloy. Acta Metall Sin, 2017, 53(12): 1620-1626.
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Abstract Recently, a new Co-Al-W-based alloy with ordered L12 structure has been attracted much attention of researchers, these alloys have higher melting point than Ni-base superalloys with morphologically identical microstructure, but grain defect formation caused by thermosolutal convection has become an important problem for its application. Magnetic field is always applied to damp the convection which reduces the formation of defects. However, there are hitherto few papers to investigate the effect of magnetic field on grain defects during Co-Al-W-based alloy directional solidification. In this work, The effect of high magnetic field on the solidification structure and macrosegregation in directionally solidified Co-Al-W-based alloy was investigated. The results showed that the application of longitudinal magnetic field can induce convection and cause deformation of the solid-liquid interface shape, forming the macrosegregation and the stray grains in the mushy zone at the pulling rate of 5 μm/s. With the increase of pulling rate, the macrosegregation and the stray grains disappeared gradually at 2 T magnetic field. While the transverse magnetic field was applied, the macrosegregation became serious and the number of the stray grains increased. The macrosegregation further became more serious and the columnar-to-equiaxed transition was induced after adding the Ta element. The main reason of undercooling nucleation and columnar-to-equiaxed transition (CET) was the microsegregation induced by thermoelectric magnetic convention.
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Received: 03 May 2017
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Fund: Supported by National Natural Science Foundation of China (Nos.51404148, 51690162 and U1560202), United Innovation Program of Shanghai Commercial Aircraft Engine (Nos.AR910 and AR911) and fund of the State Key Laboratory of Solidification Processing (No.SKLSP201602) |
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