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| THE INFLUENCE OF BORON ON POROSITY OF CAST Ni-BASE SUPERALLOYS |
| ZHU Yaoxiao;ZHANG Shunnan;XU Leying;TONG Yingjie;NING Xiuzhen;LIU Zenzhou;HOU Cuiping;BI Jing Institute of Metal Research;Academia Sinica;Shenyang |
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Cite this article:
ZHU Yaoxiao;ZHANG Shunnan;XU Leying;TONG Yingjie;NING Xiuzhen;LIU Zenzhou;HOU Cuiping;BI Jing Institute of Metal Research;Academia Sinica;Shenyang. THE INFLUENCE OF BORON ON POROSITY OF CAST Ni-BASE SUPERALLOYS. Acta Metall Sin, 1985, 21(1): 1-145.
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Abstract The influence of B content on the solidification and on the porosity forma-tion of cast Ni-base superalloys has been examined.Because of the solubility ofB in γ-solid solution is quite limited,the B may be enriched in melt at the frontof frozen solid during solidification.For superalloys containing more B,say 0.1%,the solidified grain may be surrounded by a much low melting point liquid coatingenriched with extreme B as high as 1%.It was found under metallographic obser-vation that their microstructure reveals as the interconnected continuous“web-likefilling channels”which expand the temperature range in molten state and reducethe residual amount of liquid unable to fill the pores.Thus,an improvement ofthe cast superalloys over both porosity elimination and technologic allowance hasbeen noticed.The liquid pools in alloys are small and isolated,and the micropo-rosities are finely distributed.For superalloys of normal B content,say about0.01%,the B did not be enriched to such extent that the liquid web was not yetformed.The solidified dentritic grains may be interconnected rather promptly alongcertain fastly growing directions,and the residual liquids isolated each other intolarge pools.In this case,the unsolidified liquid pools may be up to 30% in vol-ume of the alloys.Therefore,the more serious porosities will be resulted.
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Received: 18 January 1985
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