基于纳米片状粉末烧结特性的氧化物弥散增强(ODS)铁素体钢的可控制备与表征

氧化物弥散增强（ODS）铁素体钢是第四代核能系统反应堆第一壁包层最具潜力的候选材料之一。对于该材料而言，关键是控制Y2O3颗粒在铁素体内的尺度分布和位置分布。传统机械合金化（MA）法存在Y2O3易分解反应、含氧量不易控制以及微观组织复杂等缺点。粉末冶金（PM）方法可以规避上述缺点，但制备的ODS钢性能较差。申请人前期研究发现（Scripta Mater, 78–79: 1-4, 2014）纳米片状粉末具有特殊的烧结粗化行为，烧结后期粉末厚度方向生长速率高于宽度方向上的生长速率，使得氧化物颗粒被包覆在金属基体内而呈晶内弥散分布，导致材料由于具备额外的Orowan强化，弥散强化效果更显著。据此提出采用低能球磨活化铁素体预合金粉末，以高比表面积纳米片状粉末为组装单元通过PM技术制备ODS铁素体钢的工艺。本项目实施有望建立PM制备ODS铁素体钢的技术平台，为开发高性能ODS铁素体钢提供技术支撑。

Oxide dispersion strengthened (ODS) ferritic steel is one of the most promising candidates for the first wall cladding materials in the fourth-generation nuclear reactor system. For this kind of steel, the key is to control both the size distribution and the localization distribution of the Y2O3 particles in the ferrite matrix. There are some inherent weaknesses of the existing traditional mechanical alloying (MA) method, such as high risk of decomposition reaction of Y2O3 particles, poor oxygen content control and complicated microstructure. Powder metallurgy (PM) method can avoid the above shortcomings, but the mechanical performances of the ODS steel prepared by PM method are unsatisfactory. Based on our previous work (Scripta Mater, 78–79: 1-4, 2014), nano flake powders have special sintering coarsening behaviors. The coarsening rate through thickness direction of the flake powder is faster than that of through width direction during sintering. Thus, oxide particle is enveloped by the growth of the two neighboring flakes and has intragranular distribution in the ferrite matrix finally, which results in higher dispersion strengthening contributions due to the additional Orowan strengthening effect. In view of the above, the applicant proposed here to use the low energy ball milling (LEBM) to activate the pre-alloyed ferritic steel powders, and use the nano flake powders with high specific surface area as building blocks to assemble into ODS ferritic steel via PM method. The platform for ODS ferritic steels prepared by PM technique can be established through this project. And some constructive suggestions for fabricating high performance ODS ferritic steels will be put out.