李远士
,
牛焱
,
吴维(山文)
金属学报
doi:10.3321/j.issn:0412-1961.2000.07.016
研究了三元双相Cu-30Ni-25Fe合金在700-900℃空气中的氧化.在相同温度下合金的氧化速率都低于纯铜的,700-800℃的氧化动力学为抛物线规律,在900℃初期为抛物线规律,后期变为线形规律.氧化膜最外层为近乎纯的氧化铜;内层是由三种金属组元的氧化物及组元间的复合氧化物所构成的混合区域.另外,在外氧化膜下面发生了Fe和Ni的内氧化,而内氧化区前沿的合金中仍保持为双相结构.该合金中难以发生Fe的选择性外氧化,这是组元间较小互溶度及合金双相结构限制了Fe的扩散的结果.
关键词:
Cu-Ni-Fe
,
双相合金
,
氧化
江伯鸿
,
张美华
,
魏庆
,
徐祖耀
金属学报
从三元系自由能对成分的Taylor展开,导出三元调幅分解的热力学判据为G_(xx)(δ_x)~2+2G_(xy)δ_xδ_y+G_(yy)(δ_y)~2<0,据此引出调幅分解的各种条件:当G_(xx)<0,G_(xy)~2-G_(xx)G_(yy)<0,为不受成分起伏方向约束的不稳定分解,当G_(xx)<0,G_(xy)~2-G_(xx)G_(yy)>0以及G_(xx)>0,G_(xy)~2-G_(xx)G_(yy)>0或G_(xx)=0均为受成分起伏方向约束的不稳定分解,相应的成分起伏δ_x,δ_y需满足一定的条件。由此可以解释调幅分解过程中发生的成分转动现象.以Cu-Ni-Fe系为例根据以上三元调幅分解的判据由计算机计算不稳定分解区域的范围与文献报道的实验结果相符。
关键词:
调幅分解
,
thermodynamics
,
criterion
,
CuNiFe system
JIANG Bohong ZHANG Meihua WEI Qing XU Zuyao(T.Y.Hsu) Shanghai Jiaotong University
,
Shanghai
,
China
金属学报(英文版)
By expanding the Gibbs free energy of a ternary system into a Taylor series with respect to the composition,a thermodynamic criterion of spinodal decomposition is conducted as G_(xx)(δx)2+2G_(xx)δxδy+G_(yy)(δy)~2<0,from which,various conditions of spinodal decomposition are discussed.When G_(xx)<0 G_(xy)~2-G_(xx)G_(yy)<0,it is called unstable decomposition unrestricted by the direction of composition fluctuation;when G_(xx)<0,G_(xy)~2-G_(xx)G_(yy)>0,or G_(xx)>0, G_(xy)~2-G_(xx)G_(yy)>0,as well as G_(xx)=0,are all considered as unstable decomposition restricted by the direction of composition fluctuation δx and δy.The phenomenon of turning round in composition during spinodal decomposition is attempted to be explained from above point of view.The computer calculated ranges of unstable decomposition according to the criterion of spinodal decomposition on Cu-Ni-Fe ternary system is consistent with the experimental re- sults obtained from literatures.
关键词:
spinodal decomposition
,
null
,
null
