Cr-Ti-Y-O型纳米团簇氧化物弥散强化CLAM钢的研究

Oxide dispersion strengthened (ODS) reduced activation ferritic/martensitic (RAFM) steels, which produced by mechanical alloying (MA) of the elemental (or prealloyed) metallic powder with yttria (Y2O3) oxide powder and consolidated by hot extrusion or hot isostatic pressing, are promising candidate materials for the key parts in the future fusion reactor. These materials are attractive due to their excellent high temperature mechanical properties and good resistance to nuclear irradiation due to the dispersion of thermally stable oxide nanoparticles into the ferritic matrix. There are several drawbacks for the preparation of ODS RAF steels: firstly, the high temperature creep property is worse due to the high oxygen absorption of the refined powders; secondly, there existed high porosity after hot consolidation because the high hardness of powders induced by MA strain hardening. The existence of porosities resulted in the deleterious properties such as ductility, creep and irradiation resistant. A plan for the pre-MA Cr-Y or Cr-Ti-Y and the following low temperature hydrogen annealing is proposed for the decreasing of oxidation of powders. It will decrease the ODS sintered porosity of compact after short-time low temperature annealing. The research will be carried out for the double-step MA and hydrogen annealing of the ODS steel. It will provide the theoretic and experimental basis for the candidate materials of the fusion reactor key parts through controlling the effects of the amount of oxygen and sintered porosity for the mechanical properties.

低活化氧化物弥散强化钢（ODS钢）具有高强度和优异的抗辐照性能，是核聚变堆用关键部件备选材料。ODS钢主要是通过机械合金化实现氧化物固溶、纳米尺度弥散分布而制备的粉末冶金材料，目前这种粉末冶金法制备的ODS钢在工艺上存在的不足是：①制备过程中由于粉体表面活性高导致增氧严重，不利于高温蠕变强度的提高；②粉体球磨过程中的加工硬化导致粉体表面硬度高，加大了烧结难度，不利于孔隙率的降低，而孔洞的存在严重影响材料韧性、蠕变性能和抗辐照性能。本课题拟采用预球磨Cr-Y或Cr-Ti-Y，并结合低温氢气还原的方法对粉体进行终脱氧来解决粉体增氧问题。对粉体进行保护气氛下短时退火处理，在保证晶粒度轻微变化的同时降低球磨粉体的表面硬度，降低烧结后ODS钢的孔隙率。将通过预球磨和氢气还原的ODS钢研究，探索粉体氧含量和孔隙率的控制对性能影响的机制，为发展核聚变堆用关键材料提供技术和理论基础。

氧化物弥散强化ODS钢（Oxide dispersion strengthened steel）因其优异的高温力学性能和抗辐照能力，被认为是聚变堆第一壁结构材料的主要候选材料之一。ODS钢通过机械合金化实现氧化物固溶、纳米尺度弥散分布而制备出粉末冶金材料，ODS钢在制备过程中氧含量的控制技术是获得高质量ODS钢的瓶颈。本项目的主要研究内容就是在课题组前期中国低活化钢（China Low Activation Martensitic steel）的研究基础上，采用两步机械合金化、复合添加Cr-Y、Cr-Ti-Y等制备富含Cr-Ti-Y-O型纳米氧化物颗粒的ODS钢的技术路线。研究了球磨时间、成分配比等对粉体的影响规律，对制备过程中的粉体增氧问题和氢气还原方法对粉体氧含量的控制技术进行了深入研究，获得了升温过程中预球磨粉中的相变化规律，以及制备后的ODS-CLAM钢的显微组织特征和高温力学性能的情况。所获得的重要结果和关键数据如下：1)最佳球磨工艺（CLAM+Cr-Y（9:1）/ Cr-Ti-Y（9:0.5:1）），球磨时间50h，球料比10:1，球磨气氛Ar。2)氢气还原方法不适用于复合添加Cr-Y、Cr-Ti-Y、 Cr-Ti-Y2O3、Ti-Y2O3体系。3)在升温过程中，Ti/Y2O3体系的预球磨粉中成功获得了理想的Y2Ti2O7相。ODS-CLAM钢的晶粒细小，尺寸在100nm~2μm范围，基体中弥散分布了大量的富Cr-Ti-Y-O的纳米相，尺寸在3~10nm。4) ODS-CLAM钢的强度超出了CLAM钢一倍以上，同等强度下，ODS-CLAM钢的使用温度较CLAM钢提高了100℃以上，700℃ODS-CLAM钢的抗拉强度在370MPa左右，屈服在280MPa左右。5）孔隙的存在会严重影响ODS-CLAM钢的性能，导致ODS-CLAM钢热加工性能下降。.本项目提供了丰富的制备ODS-CLAM钢的数据，确定了添加Y2O3、Cr-Y、Cr-Ti-Y、Cr-Ti-Y2O3和Ti-Y2O3的ODS钢的科学制备工艺路线，为我国聚变堆第一壁用CLAM钢的粉末冶金化制备出ODS-CLAM钢迈出了坚实的一步。