Simulation for early precipitation process of Ni75Al4V21 alloy by microscopic phase-field model
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摘要: 采用三元体系微观相场动力学模型,对较低铝浓度的Ni75Al4V21合金中γ′相和θ相沉淀早期进行计算研究,模拟了合金的原子图像演化过程,并计算了θ(Ni3V)相和γ′(Ni3Al)相的相内成分序参数分布和长程序参数分布.结果表明,θ相先析出,其沉淀机制为等成分有序化+失稳分解,等成分有序化产生非化学计量比的单相θ有序畴,并被相界分开,失稳分解为一特殊的分解类型,主要发生在相界处,形成化学计量比θ有序相;此失稳分解过程同时又是γ′相在θ相界处以非经典异相形核方式析出的过程,先形成非化学计量比γ′有序相,并逐渐长成为化学计量比γ′有序相,从而形成2种有序相共存的组织形态.
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关键词:
- γ′相和θ相 /
- Ni75Al4V21合金 /
- 沉淀过程 /
- 相场法模拟
Abstract: The microscopic phase-field kinetic model for ternary system was applied to investigate the precipitation process of γ′ and θ phase in Ni75Al4V21alloy. The evolution of atomic pictures was simulated, and the composition and long-range order parameters of θ (Ni3V) and γ′ (Ni3Al) were calculated. The results show that θ forms earlier, its precipitation mechanism is congruent ordering followed by spinodal decomposition; By congruent ordering, a nonstoicheometric single θ ordered phase is produced with the order domains being separated by phase boundaries; Spinodal decomposition occurs predominantly at phase boundaries, and then the stoicheometric θ phase is formed; At the same time, γ′ (Ni3Al) appears at phase boundaries of θ phase by nonclassical different phase nucleation mechanism, the nonstoicheometric γ′ phase forms earlier and gradually transforms into the stoicheometric γ′ phase, so two kinds of ordered phases appear simultaneously in the system.-
Key words:
- γ′ and θ ordered phase /
- Ni75Al4V21 alloy /
- precipitation process /
- phase-field model
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