基于原位中子小角散射的抗辐照ODS钢中Y-Ti-O纳米团簇的反应机理研究

Oxide dispersion strengthened (ODS) steels are presently considered as promising structural materials for Gen. IV nuclear fission reactors and future fusion reactor due to the extraordinary irradiation resistance and high temperature creep property. The void swelling resistance of ODS steel is mainly determined by the average radius and number density of Y-Ti-O nanoclusters. Therefore, odulation,characterization and reaction mechanism of Y-Ti-O nanoclusters during preparation process remain the most important scientific issues for ODS steels..As a non-destructive tool in material study at the nanoscale, small angle neutron scattering (SANS) enables real-time in-situ monitoring of Y-Ti-O nanoclusters in both ODS steel powders and bulk sample, giving statistical data representative of the bulk sample. In this project, Y-Ti-O nanoclusters in ODS steels will be characterized mainly by in-situ Small Angle Neutron Scattering (SANS) technique to obtain key parameters including average particle size and number density. Present research aims to reveal the reaction mechanism of Y-Ti-O nanoclusters during the preparation process, consisting of solid solution behavior of initial added yttria under variant mechanical alloying conditions and re-precipitation behavior during sintering process. A combination of in-situ SANS, TEM and APT allows a comphrehensive investigation of Y-Ti-O nanoclusters in ODS bulk samples, which will provide reliable fundamental data for radiation resistance predication.and a thorough understanding of microstructure-dominated mechanism for ODS steels.

氧化物弥散强化（Oxide dispersion strengthened，ODS）钢由于优异的抗辐照性能和高温蠕变性能，成为第四代裂变堆和核聚变堆的最有希望的候选材料。其抗辐照肿胀性能取决于Y-Ti-O纳米团簇的平均粒径和数密度。因此Y-Ti-O团簇在制备过程中的调控、表征及反应机理一直是ODS钢研究的重要科学问题。小角中子散射作为一种纳米结构的无损检测技术，能够实现对ODS钢粉末及块体中Y-Ti-O纳米团簇的实时原位监测。本课题拟通过原位小角中子散射技术获得Y-Ti-O纳米团簇的平均粒径、数密度、体积分数等关键参数，旨在揭示Y-Ti-O纳米团簇在制备过程中的反应机理，包括氧化钇在机械合金化过程中的固溶规律及Y-Ti-O纳米团簇在烧结中的再析出行为。结合TEM、APT等技术实现ODS钢块体材料中纳米第二相的综合表征，为ODS钢抗辐照性能的预测及微观调控机理的研究提供较为全面的基础数据。

小角中子散射作为一种纳米结构的无损检测技术，能够实现对ODS钢制备过程中Y-Ti-O纳米团簇的实时原位监测，为ODS钢制备工艺的优化和抗辐照性能的预测提供基础数据。本项目在“团簇+连接原子模型”的合金设计方法指导下，通过小角中子散射、透射电镜等实现了对工艺、组织结构的综合调控，获得了公斤级的高性能ODS钢样品。通过小角中子散射研究了合金成分和球磨时间对ODS钢中纳米团簇关键参数的影响。结果表明，对于14Cr ODS钢来说，球磨初期（5h）强烈的塑性变形带来了氧化钇颗粒细化，球磨时间延长至40h，纳米团簇的粒径分布和体积分数接近稳态，继续延长球磨时间至60h对纳米团簇影响很小。经过40h的球磨，相比FeCrWY粉末，TiH2的添加使得FeCrWYTi中纳米团簇的粒径从3.88nm和2.15nm。基于上述结果，实现了对ODS钢成分的快速筛分和制备工艺的快速优化。利用“多成分热等静压同步烧结+楔形板轧制工艺”制备了具有优异强韧性的ODS钢样品。FeCrWY ODS钢最高室温拉伸强度约为1.6GPa，延伸率为13%，在强度提高1倍的同时，延伸率仍有所提高。其在700℃拉伸强度为210MPa，延伸率为45%，约分别提高了75%和20%。该项目为揭示纳米团簇的演变机理和ODS钢的强韧化机制提供了科学支撑。