Anisotropic mechanical properties of the MA956 ODS steel characterized by the small punch testing technique

• Published in: Journal of nuclear materials 2012-09, Vol.428 (1-3), p.76-81
• Main Authors: Turba, K., Hurst, R.C., Hähner, P.
• Format: Article
• Language: English
• Subjects: Anisotropy; Applied sciences; Chromium; Controled nuclear fusion plants; Dispersions; Embrittlement; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Fracture mechanics; Fuels; Installations for energy generation and conversion: thermal and electrical energy; Mechanical properties; Nuclear fuels; Punches; Steels
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2011.08.042

► Small punch testing is used to assess creep and fracture properties of MA956 ODS steel. ► MA956 exhibits strong anisotropy in both DBTT and creep resistance at 725°C. ► High DBTT and susceptibility to thermal embrittlement potentially dangerous for applications. The small punch testing technique was used to assess both creep and fracture properties of the MA956 oxide dispersion strengthened ferritic steel. The anisotropy in mechanical properties was addressed, as well as the alloy’s susceptibility to thermal embrittlement. Strong anisotropy was found in the material’s creep resistance at 725°C for longer rupture times. Anisotropic behavior was also observed for the ductile–brittle transition temperature (DBTT). The origin of the anisotropy can be related to the strongly directional microstructure which enables a large amount of intergranular cracking during straining at both high and low temperatures. The DBTT of the alloy is very high, and can be further increased by at least 200°C after 1000h of ageing at 475°C, due to the formation of the Cr-rich α′ phase. The particularly high susceptibility of the MA956 to thermal embrittlement is mainly a consequence of its high chromium content.