铌熔点高、延性好、强度高，兼具固溶强化和沉淀强化作用，含铌镍基合金室温延性低和高温抗蠕变强度低限制了其应用，该类合金主要强化相为与基体共格的沉淀亚稳相。因此，研究铌含量和共格弹性场对镍基合金沉淀亚稳过程的影响在提高其性能方面具有重要意义。本项目主要采用基于原子-相-组织尺度的四元微观离散格点相场方法，从基于电子-原子尺度的第一性原理计算中获取所需参数，计算不同含铌量合金在不同程度弹性场作用下沉淀亚稳相的原子占位、有序-无序、簇聚、体积分数、标度律等，重点研究沉淀相的早期析出序列、中间亚稳现象、后期粗化规律、全程形貌演化；之后再与第一性原理的热力学、力学性质计算相复合，研究各亚稳相的热力学稳定性、强度、塑性等宏观性能，并进行实验验证。本项目实施会为含铌镍基合金的成分设计和强化设计提供指导，并提高相场模拟的可靠性，同时期待为第一性原理计算配套一种不预设微结构和转变路径的动力学描述方法。

Niobium has high melting point, ductility strength, and the effect of solution strength and precipitation strength, Yet the low room temperature ductility, high temperature creep strength of Nickel based alloys containing Nb limit its application. The main strengthening phases are some metastable precipitates coherent with their matrix. So it is important to study the influence rule of niobium content and elastic distortion field on the metastable precipitation process of nickel alloy for increasing the room-temperature and high-temperature properties. Here, the main modeling method of Micro Phase Field Method-MPFM for four componets alloys system based on atom-phase-microstructure scale will be developed and employed, and some required parametres will be acquired by First Principles Method-FPM based on electronic-atomic scale. The occupied sites, order-disorder, clustering, volume fraction, scaling law etc. of precipitated metastable phases for different niobium content alloy at different degree of elastic field will be calculated, and the project planed to focus on studying the early precipitation sequence, the middle metastable phenomenon, the later coarsening law and the whole course morphology evolution of precipitation phases. Then the results were compounded with thermodynamic and mechanical properties of first-principles calculation to study the macroscopical preperties of each metastable phase, such as thermodynamic stabilities, strength and plasticities, and were verified through experiments. The project will provide direction for component and strengthening design of nickel alloy added by niobium and increase the reliability of phase field simulation, and expect to match a kind of process description approaching the fact well without model and route with the states and properties of first-principles calculation.