Abstract:Microscopic phase-field method was used to simulate the site occupation of a series of alloys with a stoichiometric composition of Ni₇₅Al_25-xFe_x (x=0, 5-10) aged at 1273 K. With the change of Fe content, quantitative calculations were made on each atomic site occupation probability (SOP) in L1₂-Ni₃ (Al_1-xFe_x), so as to find out the dynamic response law. The result of the study shows that, with the increase of Fe content, the Fe atom preferentially occupies the B sites (corner sites of FCC) with its SOP value being increased gradually, and the SOP of the Al atom on the B sites is greatly decreased. Meanwhile, Al_Ni and Fe_Ni anti-sites form in the precipitation of L1₂ phase. Moreover, with the increase of Fe content, the formation of Al_Ni and Fe_Ni anti-sites becomes much easier. In addition, it has been found that the instantaneous dynamic evolution of the atomic SOP is completed at the early stage of the growth of L1₂ phases.

Key words: intermetallics; Ni₇₅Al_25-xFe_x alloy; atomic site occupation; precipitation; microscopic phase-field