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铁道科学与工程学报

JOURNAL OF RAILWAY SCIENCE AND ENGINEERING

Vol. 18    No. 1    January 2008

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Microscopic phase-field simulation of atomic site occupation in ordering process of NiAl9Fe6 alloy
LIANG Min-jie(梁敏洁), CHEN Zheng(陈 铮), ZHANG Ji-xiang(张济祥), WANG Yong-xin(王永欣)

School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an710072, China

Abstract:The process of γ(fcc)→γ(fcc)+γ′(L12) phase transformation was simulated by using microscopic phase-field method for the low supersaturation NiAl9Fe6 alloy. It is found that in the γ′ phase, the ordering degree of Al atoms is obviously higher than that of Fe atoms, and the ordering of Al atoms precedes their clustering, while the case of Fe atoms is opposite. The α site is mainly occupied by Ni atoms, while the β site is occupied in common by Al, Fe and Ni atoms. At order-disorder interphase boundary, the ordering degree of Al atoms is higher than that of Fe atoms, and at the β site, the Fe atomic site occupation probabilities vary from high to low during ordering; the Al atomic site occupation probabilities are similar to those of Fe atoms, but their values are much higher than those of Fe atoms; Ni atoms are opposite to both of them. Meanwhile, during the ordering transformation, γ′ phase is always a complex Ni3(AlFeNi) single-phase, and it is precipitated by the non-classical nucleation and growth style. Finally, in the alloy system, the volume of γ′ ordered phase is less than that of γ phase, and the volume ratio of order to disorder is about 77%.

 

Key words: microscopic phase-field; Ni-Al-Fe alloy; γ′(L12); site occupation; ordering

ISSN 1672-7029
CN 43-1423/U

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