基于低能界面和强磁场调控的强有序析出增强超高强钢合金设计及强韧化机制

According to the present scientific research status on heterogeneous nucleation of nano-scale precipitates and trade-off between strength and toughness in Cu-bearing steels, in this proposal, an alloy-design strategy for strengthening-toughening is proposed, in which both the low misfit and coherent high-density homogeneous precipitates and twin-structure precipitates contribute to strength by precipitation strengthening, and hierarchical structures combined secondary sub-micro precipitates heterogeneously nucleated contribute to toughening and ductility. The theoretical framework is originated from both the alloy-design of low-energy coherent interfaces and twin interfaces, and high-magnetic-field impact on precipitation nucleation if there is difference in magnetic susceptibility between matrix and secondary-phase. Thermodynamics and kinetics simulation are first executed to establish a new essential alloy system. By adjusting alloy composition, heat treatment and external high magnetic field, and aiming at forming two kinds of low-energy interfaces including low misfit and coherent high-density homogeneous precipitates and twin-structure precipitates, several central questions as multicomponent new alloy-design of super-high strength steels, the synergistic effect of two types of precipitates regulated by high magnetic field, and formation of hierarchical structures and the influence on strengthening-toughening are explored. A new multicomponent alloy system based on low-energy interface and with super-high strength will be suggested. The synergistic effect of two types of precipitates regulated by high magnetic field will be also revealed. The new strategy of strengthening-toughening for super-high strength steels and analogous alloy systems will be built up. The strengthening-toughening of super-high strength steels will be achieved. The proposal will provide fundamentals for alloy-design strategies of analogous alloy systems.

针对含Cu超高强钢中纳米析出相异质非均匀形核和强韧性呈倒置关系的研究现状，本项目提出利用低错配共格高密度均匀析出相和孪晶结构析出相构建复合强有序析出强化，与二次亚微米析出相构筑的分层结构提供塑韧性的先进合金设计学术思想，基于共格和孪晶低能界面合金设计和强磁场促进与母相不同磁化率析出相析出行为的理论框架，在热力学和动力学模拟基础上，通过调整合金成分、热处理和外加强磁场等析出相的形核生长调控因素，以形成与基体低错配度的析出相及孪晶结构析出相的低能界面为目标，探索多组元超高强钢新合金体系成分设计、强磁场调控新合金体系纳米析出相协同析出机制和分层结构构筑及其强韧化等核心内容，提出基于低能界面多组元超高强钢新合金体系，揭示低错配共格强化与孪晶强化的协同形核生长及强磁场调控新理论，形成超高强钢及类似合金系统强韧化控制新方法，实现超高强钢新合金体系的强韧化，为同类合金设计提供理论基础。

强度和塑韧性的平衡一直是结构材料领域关键的科学难题。针对在航空航天、核电压力容器、汽车板、航母和舰艇等重大战略领域不可或缺的含Cu高强结构用钢中纳米析出相异质非均匀形核和强塑韧性呈倒置关系的研究现状，本项目提出基于低能界面构建多组元超高强新合金体系，调控纳米共格析出和孪晶等交互作用，提升强塑性。主要研究结果包括：. （1）基于孪晶、共格等低能界面合金设计理论，提出新型多组元合金体系。研究以孪晶、富Cu相、NiAl相、Laves相和碳化物等为主的多组元合金体系，揭示不同析出相与界面的交互作用机制，丰富低能界面合金设计理论，为新型多组元合金体系的构建奠定实验和理论基础。. （2）揭示复合纳米析出及其与孪晶界面交互作用。建立铁素体钢中复合析出相形核生长动力学，构建Mo合金化调控多种类型纳米析出相的形核生长机制，揭示新型多组元合金复合析出相的形核生长及调控机制。阐明孪晶界面与纳米析出行为交互作用，丰富孪晶和纳米析出相等强塑性调控机理。. （3）揭示新型多组元合金多尺度微观组织对强塑性的影响机制。阐明奥氏体、铁素体和马氏体等多组元合金体系中多尺度复合纳米析出相、孪晶诱导塑性（TWIP）和相变诱导塑性（TRIP）等对强塑性影响机理。提出强磁场作用下多组元合金强塑性提升的新型工艺技术。. 本项目的顺利实施丰富了低能界面及其强塑性调控理论，也为新型多组元合金强塑性的强磁场控制理论发展提供可行性依据，对于解决金属材料强塑韧性的科学难点具有重要理论意义和实用价值。