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Progress in Natural science:materials International 2005年第12期15卷 1104-1109页

作者： lu yanli,chen zheng,li yongsheng,wang yongxin and chu zhong state key laboratory of solidification processing,school of materials science and engineering,northwestern polytechnical university,xi’an 710072,china state key laboratory of solidification processing School of Materials Science and Engineering Northwestern Polytechnical University Xi'an 710072 China

The early precipitation process of Ni-Al alloy was studied on the atomic scale based on the microscopic phase-field kinetic *** investigated the effect of elastic strain energy on precipitation mechanism and morphological evolution of the *** results show that at the early stage of precipitation,γ’ ordered phase presents non-directional and irregular shape during the process of aging,the γ’ ordered phases change into the quadrate shape and their orientations become more obvious; at the later stage,the γ’ precipitates present quadrate shape with round corner and align along the [100] and [010] *** mechanism of early precipitation for Ni-13at.%A1 alloy is the mixed mechanism of non-classical nucleation growth and spinodal decomposition and near to non-classical nucle-ation growth,and the mechanism of early precipitation for Ni-15.8at.% Al alloy is the mixed mechanism of non-classical nucleation growth and spinodal decomposition and near to spinodal decomposition.

关键词： Ni-Al alloy early precipitation microscopic phase-field simulation elastic strain energy

Atomic-scale computer simulation for ternary alloy Ni-Cr-Al during early precipitation process

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Progress in Natural science:materials International 2005年第7期15卷 656-660页

作者： chu zheng , chen zheng, wang yongxin, lu yanli and li yongsheng (state key laboratory of solidification processing, northwestern polytechnical university, xi’an 710072, china) state key laboratory of solidification processing Northwestern Polytechnical University Xi'an 710072 China

The aging behaviors of Ni-Cr-Al ternary alloy are studied at temperature 873 K based on the mean-field theory, and the early precipitation process is simulated at atomic-scale with microscopic phase-field model. The precipitation mechanism of the low supersaturated alloy Ni-12.2at. %Cr-7.8at. %Al is non-classical nucleation and growth, the L12 structure (Ni3Al) and D022 structure (Ni3Cr) phases precipitate simultaneously, a part of D022 phase transmits to Ll2 structure phase, and other part retains its previous structure. For high supersaturated alloy, congruent ordering appears first, then followed by spinodal decomposition, the nonstoicheometric ordered phases are produced in this process, which occurs before clustering. The precipitation mechanism of Ni-8at. %Cr-18at. % Al alloy is similar to Ni-10at. %Cr-12at. %AI alloy, but the ordering process of the former is ahead of the latter.

关键词： microscope phase-field model Ni-Cr-Al precipitation ordering parameter simulation.

Microscopic Phase-field Simulation of Competition Mechanism Between Ll_2 and D0_(22) Structure in Ni-Cr-Al Alloy

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Journal of materials science & Technology 2006年第3期22卷 315-320页

作者： zhong chu zheng chen yongxin wang yanli lu yongsheng li state key Lab of solidification processing Northwestern Polytechnical University Xi＇an 710072 China

Simulations are performed on temporal evolution of atom morphology and ordering parameters of Ni-14.5 Cr-16.5 Al alloy during early precipitation process at different temperatures based on microscopic phase-field theory; the relationship between precipitation sequence and mechanism of L12 and D022 structure and precipitation temperature are illuminated. The nonstoichiometric ordered L12 phases appear first with congruent ordering＋spinodal decomposition mechanism which is then followed by precipitation of D022 phases at ordering domain boundaries of L12 phases by spinodal decomposition mechanism at 1073 K and 1223 K. The nonstoichiometric L12 phases transform to stoichiometric ordering phases gradually. The incubation period of L12 and D022 phases is shorter at 1073 K than that 1223 K, and growth speed is higher at 1073 K. At 1373 K, L12 and D022 phases appear simultaneously by non-classical nucleation and growth mechanism. After that the particles of D022 phases diminish and disappear gradually; L12 phases grow and single L12 phases are remained at last.

关键词： Ni-Cr-Al Microscopic phase-field model Precipitation Ordering parameter Simulation

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Microscopic phase-field simulation of L1_2 and D0_(22) phases during the early precipitation process of Ni-Cr-Al alloys

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Journal of university of science and Technology Beijing 2006年第5期13卷 429-434页

作者： zhong chu zheng chen yongxin wang yanli lu yongsheng li state key laboratory for solidification processing Northwestern Polytechnical University Xi＇an 710072 China

The influence of temperature on the precipitation mechanism and sequence of L 12 and D022 phases during the early precipitation process of a ***%Cr-14at%Al alloy was simulated based on the microscopic phase-field model. In the range from 873 to 1373 K, the precipitation mechanism transformed from spinodal decomposition to non-classic nucleation and growth; the incubation period prolonged gradually with increasing temperature. The volume fraction of L12 phases increased and that of D022 phases decreased. D022 phases disappeared at 1373 K, and finally single-phase L12 phases were formed.

关键词： Ni-Cr-AI alloys microscope phase-field model precipitation ordering parameter simulation

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