热力耦合下FeCuMnNi系合金含缺陷沉淀微结构演变多级相场研究

核反应堆压力容器的基础材料FeCuMnNi系合金，长时间在热力耦合环境下服役，内部晶体缺陷及纳米析出相等导致材料硬化和脆化，严重影响服役安全，针对该非平衡沉淀过程及内部微结构交互作用机制进行研究意义重大。本项目基于相场理论模型，将平均原子密度序参量ρ，原子占位几率序参量P，组元浓度场序参量C和结构转变序参量η，关联在一个统一的多级相场模型框架内；多路径耦合第一性原理计算，结合沉淀结构特征，应力时效和微观分析，追踪非均匀多元多相系统的粒子扩散过程，研究温度、应变诱发动态预析出相、亚稳相、稳定相、晶体缺陷的形成、演化和转变等；探明热力耦合条件下多（主）元体系缺陷和纳米沉淀交互作用机制，明晰成分、温度、第N组元（2≤N≤7）及应力响应关系，揭示各种微结构要素对应变诱发沉淀过程的影响规律；结合实验和理论分析，验证模型及结果的可靠性，并指导设计新型高性能FeCuMnNi系结构材料。

FeCuMnNi based alloys, the basic materials of nuclear reactor pressure vessel, have been in service for a long time under the thermos-mechanical coupling environment. The internal crystal defects and nano precipitates lead to the hardening and embrittlement of the materials, which seriously affects the service safety. Therefore, it is of great significance to study the non-equilibrium precipitation process and the interaction mechanism of internal microstructure. Based on the phase field model, the average atomic density order parameter ρ, atomic occupation probability order parameter P, component concentration field order parameter C and structural transformation order parameter η are associated in a unified multi-level phase field model framework. By coupling the first principle calculation in various ways, combining with the precipitation structure characteristics, stress aging and micro analysis, the particle diffusion process of heterogeneous multiphase system is tracked, and the formation, evolution and transformation of dynamic pre precipitation phase, metastable phase, stable phase and crystal defects induced by temperature and strain are studied. The interaction mechanism of defects and nano precipitation in the multi-element system under the condition of thermo mechanical coupling is explored. The purpose of this work is to clarify the response relationship of composition, temperature, the component N (2 ≤ N ≤ 7) and stress, reveal the influence law of various microstructure elements on the process of variable induced precipitation, verify the reliability of the model and results, and guide the design of new high-performance FeCuMnNi based system structural materials by combining experimental and theoretical analysis.