Fabrication of porous iron by unidirectional solidification in nitrogen atmosphere
Fabrication of porous iron by unidirectional solidification in nitrogen atmosphere
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DOI：
10.2320/matertrans.43.526
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发表时间：
2002-03-01
影响因子：
1.2
通讯作者：
Nakajima, H
中科院分区：
文献类型：
--
作者：
Hyun, SK;Nakajima, H
在氮气和氩气的混合气体中，通过熔体的定向凝固制备出了长圆柱形孔沿一个方向排列的多孔铁。由于氮在液体和固体之间的溶解度差异，溶解在铁液中的氮在凝固过程中被排斥在固液界面，气孔是由不溶于固体铁中的氮形成的。它们单向生长。在熔化和凝固过程中，气孔率受氮气分压和氩气分压的控制，在一定的氮气分压下，气孔率随氩气分压的增加而减小，遵循波义耳定律。在混合气体总压恒定的情况下。孔隙率随着氮分压的增加而增加，并且在低于氮的临界分压的凝固过程中不形成孔。固体铁中的氮浓度随着氮分压的增加而增加。在铸态多孔铁中观察到固溶硬化，而在1273 K高温淬火的多孔铁中也发现了更显著的硬化，这是由于马氏体相变。
Porous iron whose long cylindrical pores are aligned in one direction has been fabricated by unidirectional solidification of the melt in a pressurized mixture gas of nitrogen and argon, Nitrogen dissolved in the molten iron is rejected at the solid-liquid inter-face during the solidification due to the solubility difference of nitrogen between the liquid and solid, The gas pores are evolved from the nitrogen insoluble in the solid iron. which grow unidirectionally. The porosity is controlled by the partial pressures of nitrogen and argon during melting and solidification, The porosity decreases with increase of the partial pressure of argon at a given nitrogen pressure according to the Boyle's law. At a constant total pressure of the mixture gas. the porosity increases with increasing partial pressure of nitrogen and no pores are formed during solidification below a critical partial pressure of nitrogen. The nitrogen concentration in the solid iron increases with increasing partial pressure of nitrogen. The solid-solution hardening has been observed in as-cast porous iron, while more significant hardening has also been found in the porous iron quenched from a high temperature 1273 K, which is due to the martensitic transformation.