Evolution of microstructure and mechanical properties of 9Cr ferrite/martensite steels with different Si content after long-term aging at 550 degrees C
Evolution of microstructure and mechanical properties of 9Cr ferrite/martensite steels with different Si content after long-term aging at 550 degrees C
复制标题
不同Si含量9Cr铁素体/马氏体钢550℃长期时效后显微组织和力学性能的演变
DOI：
10.1016/j.jallcom.2021.159817
复制
发表时间：
2021
影响因子：
6.2
通讯作者：
Wang Yuan
中科院分区：
文献类型：
--
作者：
Zhang Yiyong;He Hao;Wang Hui;Chen Guang;An Xuguang;Wang Yuan
为了开发用于先进的第四代铅冷快堆（LFR）燃料包壳材料的新型合金，研制了4种不同Si含量的9 Cr铁素体/马氏体（F/M）耐热钢。在本工作中，9 Cr F/M钢在550 °C的空气中进行了500，1000，2000和5000 h的长期热时效。利用OM、SEM、EBSD和TEM等技术研究了显微组织的演变过程。通过室温拉伸试验评价了热老化后力学性能的变化。在长期时效过程中，4种钢的显微组织均表现出较高的热稳定性，M23 C6碳化物和MX碳氮化物也保持不变。时效5000 h后，4种钢中均形成了新的Fe 2 W型Laves相，9 Cr-1 Si钢中的Laves相平均尺寸为94.8 ± 17 nm。时效2000 h后的拉伸性能与原始状态相比几乎没有变化。热暴露5000 h后，4种9 Cr F/M钢的强度均因细小Laves相颗粒的析出强化作用而提高。Si对9 Cr F/M钢有一定的固溶强化作用。随着Si含量的增加，Laves相的体积分数增加。当Si含量为1%时，显微组织中存在残余高温铁素体，但对9 Cr F/M钢的力学性能没有不利影响。综合考虑显微组织和力学性能，硅的加入量以不超过0.7%为宜。
In view of developing novel alloys for applications in advanced Generation IV lead-cooled fast reactor (LFR) fuel cladding materials, four 9Cr ferrite/martensite (F/M) heat resistant steels with different Si content were developed. In the present work, the long-term thermal aging of 9Cr F/M steels was carried out in air at 550 °C for 500, 1000, 2000 and 5000 h. The microstructural evolution was investigated based on OM, SEM, EBSD and TEM technologies. The changes of mechanical properties after thermal aging were evaluated by room temperature tensile test. During long-term aging, the microstructures of all four steels exhibited highly thermal stability, and M23C6carbides and MX carbonitrides also remained unchanged. Meanwhile, after aging for 5000 h, a new Fe2W-type Laves phase formed in all four steels with an average size of 94.8 ± 17 nm in 9Cr-1Si steel. The tensile properties of all samples aged for 2000 h exhibited almost no change compared with the as-received ones. However, after thermal exposure for 5000 h, the strength of all four 9Cr F/M steels increased due to the precipitation strengthening effect of the small Laves phase particles. Silicon exerted a certain degree of solid solution strengthening effect for 9Cr F/M steels. The volume fraction of Laves phase increased with the increase of Si content. As the Si content was 1%, residual high-temperature ferrite was found in the microstructure, but it has no detrimental effect on the mechanical properties of 9Cr F/M steels studied in the present work. Comprehensively considering the microstructure and mechanical properties, the suitable addition of Si content did not exceed 0.7%.