Abstract
► 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 1000 h 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.
Published Version
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