Ni75Cr25-xAlx合金中L12相和D022相形核孕育期的微观相场模拟

基于微观相场动力学模型,运用原子图像、平均长程序参数和平均成分偏离序参数,研究了Al浓度对Ni75Cr25-xAlx合金中L12相和D022相形核孕育期的影响以及孕育期与沉淀相析出顺序之间的关系.结果表明,L12相和D022相的形核孕育期不仅与Al浓度有关,而且与两相析出的先后顺序密切相关.当Al浓度小于7.5%时,先析出相为D022相,随着Al浓度的增大,D022相形核孕育期延长,后析出的L12相的形核孕育期也延长,L12相的原子簇聚速度加快;当Al浓度大于7.5%时,先析出相为L12相,随着Al浓度的增大,L12相的形核孕育期缩短,后析出的D022相形核孕育期也缩短.当Al浓度为7.5%时,L12相和D022相几乎同时析出,两者的孕育期没有明显的差别.

Microscopic phase field simulation on the nucleation incubation period of L12 and D022 phases in Ni75Cr25-xAlx alloy

Based on the microscopic phase field dynamic model, the effect of Al concentration on the nucleation incubation period of Ni75Cr25-xAlx alloy and the relation between the incubation period and the precipitation sequence are investigated by using the atomic pictures, averaged long-range order parameters and averaged composition deviation order parameters. The simulation results show that the nucleation incubation periods of L12 and D022 phases are related not only to the Al concentration but also to the precipitation sequence. When the Al concentration is smaller than 7.5%, for the D022 phase first precipitated from the matrix, its nucleation incubation period becomes longer with the increase of Al concentration, and so is the L12 phase subsequently precipitated. When the Al concentration is larger than 7.5%, for the L12 phase first precipitated from the matrix, its nucleation incubation period become shorter with the increase of Al concentration, so is for the D022 phase subsequently precipitated. When the Al concentration is equal to 7.5%, L12 and D022 phases both precipitate almost simultaneously, and there is no obvious difference berween their nucleation incubation periods.