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应用微观相场方法计算了Ni75Al21.5Ti3.5合金873K时效时的沉淀行为。利用原子演化图、长程序参数和成分序参数的演化、有序相颗粒的平均直径、颗粒数目及合金原子在α、β位置占位几率的演化等研究手段,讨论了Al、Ti原子的有序化和原子簇聚过程;有序相的形核机制及粗化行为;原子的择优占位行为。结果表明:有序相颗粒的形核机制为失稳分解机制,Al原子基本达到有序排列,同时存在Ni-Al原子反位,Ti原子未达到完全有序排列,在γ′有序相中择优占据Al位,且有序相生成过程中,前期的生长动力学指数为1/2,后期的生长动力学指数为2/5。
The precipitation behavior of Ni75Al21.5Ti3.5 alloy at 873 K aging was calculated by microscopic phase field method. The evolution mechanism of atomic evolution, long program parameters and compositional order parameters, the average diameter of ordered particles, the number of particles and the evolution of the occupancy probability of alloy atoms in α, β sites are discussed. Ordering and atomic clustering process; nucleation mechanism and roughening behavior of ordered phase; atomic occupying behavior. The results show that the nucleation mechanism of the ordered particles is the mechanism of instable decomposition. The Al atoms are basically arranged in an orderly manner, while the Ni-Al atoms are in anti-position and the Ti atoms do not reach a completely ordered arrangement. In the γ ’ordered phase Preferentially occupy Al sites, and the order of phase formation process, the early growth kinetics index of 1/2, the latter part of the growth kinetic index of 2/5.