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| BEHAVIOUR OF Hf IN SOLIDIFICATION OF CAST Ni-BASE SUPERALLOYS |
| ZHENG Yunrong (Institute of Aeronautical Materials; Beijing) |
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Cite this article:
ZHENG Yunrong (Institute of Aeronautical Materials; Beijing). BEHAVIOUR OF Hf IN SOLIDIFICATION OF CAST Ni-BASE SUPERALLOYS. Acta Metall Sin, 1986, 22(2): 31-148.
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Abstract Results of quantitative metallography, SEM, EDAX and EMPA studies of Hf on the solidification of cast Ni-base superalloys are presented. The Hf is found to lower the liquidus temperature of the superalloys even the final solidification temperature to drop to 1130℃. The Hf may narrow down the range between temperature lost the interdendritic capillary feeding action and solidus, as well as may decrease the liquid content necessary for linking the interdendritic pools in the late solidification. The Hf-rich melts have superior fluidity, wettability and skin effect. These are the factors in increasing castability of Hf-containing superalloys. The Hf is not found in the dendritic arms of the superalloys, but is exceedingly concentrated in the narrow interdendritic zones usually in the form of Hf-rich phases. The Hf content in primary Hf-rich phases may be arranged in decreasing order of MC_(2), (Hf, Ti)_2 SC, Ni_5Hf, MC_(1) and eutectic γ'. The Hf may depress the formation temperature of primary phases. The solidification temperatures of all Hf-rich phases are lower than 1250℃. These phases may precipitate from the molten pools with Hf concentration over 13 wt-% at the late solidification and may have an intergrowth feature.
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Received: 18 February 1986
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1 郑运荣;蔡玉林,中国航空科技文献HJB 830117(1983) .
2 郑运荣;蔡玉林,金属学报,16 (1980) ,A151．
3 郑运荣;蔡玉林,王罗宝,金属学报,19 (1983) ,A190．
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6 Ouichou, L.; Lavaud. F.; Lesoult, G., Superalloys 1980, Proc. 4th Int. Symp. on Superalloys, Eds. Tien, J.K., et al, ASM, Metal Park, Ohio, 1980, p. 235．9 |
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