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采用微观相场动力学模型,在原子层面上研究Ni75AlxV25-x合金中γ′相和θ相的沉淀过程及微观结构演化。模拟实验结果表明,Al浓度对沉淀序列具有重要的影响。低Al浓度合金中,先析出θ(Ni3V)有序相,随后析出γ′(Ni3Al)有序相;中Al浓度合金中,θ有序相及γ′有序相几乎同时析出;高Al浓度合金中,γ′有序相先析出,θ有序相随后析出。沉淀过程中,θ有序相和γ′有序相长大和粗化过程中存在竞争关系,无论先析出哪种相,θ有序相在粗化的竞争过程中占有优势。因此,沉淀最后形成择优取向的显微组织。
The microstructure and phase transitions of γ ’phase and θ phase in Ni75AlxV25-x alloy were investigated at the atomic level by using the micro-phase field dynamics model. The simulation results show that the Al concentration has an important influence on the precipitation sequence. In the low Al concentration alloy, θ (Ni3V) ordered phase is firstly precipitated and then γ ’(Ni3Al) ordered phase is precipitated. In the Al alloy, the ordered phase and γ’ ordered phase precipitate almost simultaneously. In the alloy, the γ ’ordered phase precipitates first, and the θ ordered phase then precipitates. In the process of precipitation, there exists a competition relationship between the ordered phases of γ and γ ’and the coarsening process. No matter which phase is first precipitated, the θ-ordered phase has an advantage in the coarsening competition process. Therefore, the precipitate finally forms a preferentially oriented microstructure.