CoAl相强化FeCrAl基ODS合金的研究

针对铁素体ODS合金缺乏有效的高温有序强化相的问题，本项目提出在抗氧化性优异的FeCrAl基体中引入新型B2-CoAl相进行析出强化，开发兼具优异高温力学性能和抗氧化性的耐事故容限型ODS合金的新思路，重点解决沉淀相和基体相结构精确调控的难题。拟通过合金化设计降低有序相的错配度和析出势垒，形成低能相界面以提高其热稳定性；通过Co元素含量调控α-Fe/γ-Fe相转变温度，在热处理过程中促成马氏体相变，并利用相转变调控“硬-软”复合结构以实现背应力强化和合金韧性的改善。研究合金元素和热处理条件对有序相的相组成、形状和尺寸等的影响规律，掌握沉淀相析出和演变规律及相界面调控技术，揭示合金化设计原理和相平衡热力学条件、以及高强度合金的强韧性匹配机理，建立CoAl相强化FeCrAl基ODS合金组织性能调控的工艺原理和技术基础，为ODS合金新型强化相的开发及多相强化合金的强韧化技术提供思路和借鉴。

In view of the lack of effective ordered strengthening phase at elevated temperatures, this research project intends to introduce B2-CoAl phase into FeCrAl matrix with the aim to develop a new accident tolerant alloy with both high performance and excellent oxidation resistance. The main focus is on the accurate controlling of the phase structure of the precipitates and matrix. The lattice misfit and precipitation barrier are reduced based on alloying design, and the stability of the precipitates are enhanced by the formation of low energy phase interface. The phase transformation temperature of α-Fe/γ-Fe is adjusted by the content of Co, which promotes the martensitic transformation during heat treatment. At the same time, the “hard-soft” composite structure is adjusted by controlling the phase transformation, facilitating back stress strengthening effect and the amelioration of alloy toughness. The influence of alloying elements and heat treatment condition on the constituent, morphology and size of the ordered phases is investigated. The precipitation and evolution of intermetallic phase, as well as the controlling technology of phase interface are revealed. The design principle, thermodynamics of phase equilibrium and the matching between strength and ductility of high strength alloy are elucidated. The theory and technical fundaments for the controlling of microstructure and mechanical properties of CoAl strengthened FeCrAl based ODS alloy are established. The work provides some ideas and references for the development of new strengthening phases of ODS alloys and the strengthening and toughening technology of multi-phase strengthened ODS alloys.