Synchrotron study on load partitioning between ferrite/martensite and nanoparticles of a 9Cr ODS steel

• Published in: Journal of nuclear materials 2014-12, Vol.455 (1-3), p.376-381
• Main Authors: Mo, Kun, Zhou, Zhangjian, Miao, Yinbin, Yun, Di, Tung, Hsiao-Ming, Zhang, Guangming, Chen, Weiying, Aimer, Jonathan, Stubbins, James F
• Format: Article
• Language: English
• Subjects: Dispersion hardening alloys; Ferrite; Ferritic stainless steels; Martensite; Nanoparticles; Partitioning; Residual stress; Steels
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2014.06.060

Oxide dispersion strengthened (ODS) steels exhibit exceptional radiation resistance and high-tempera-ture creep strength when compared to traditional ferritic and ferritic/martensitic (F/M) steels. Their excellent mechanical properties result from very fine nanoparticles dispersed within the matrix. In this work, we applied a high-energy synchrotron radiation X-ray to study the deformation process of a DO-ODS steel. The load partitioning between the ferrite/martensite and the nanoparticles was observed during sample yielding. During plastic deformation, the nanoparticles experienced a dramatic loading process, and the internal stress on the nanopartides increased to a maximum value of 3.7 GPa, which was much higher than the maximum applied stress (~986 MPa). After necking, the loading capacity of the nanoparticles was significantly decreased due to a debonding of the particles from the matrix, as indicated by a decline in lattice strain/internal stress. Due to the load partitioning, the ferrite/martensite slightly relaxed during early yielding, and slowly strained until failure. This study develops a better understanding of loading behavior for various phases in the ODS F/M steel.