Statistical evaluation of anisotropic fracture behavior of ODS ferritic steels by using small punch tests

Small punch (SP) tests were performed to evaluate the anisotropy in the ductile–brittle transition behavior for the oxide dispersion strengthened (ODS) ferritic steel for the advanced nuclear systems. The upper-shelf energy and scattering of SP fracture energy for the specimens where the surfaces are perpendicular to the extruded direction was larger and smaller than that for the other direction, respectively. The anisotropic fracture behavior appears to be mainly caused by the favorable cracking path along the elongated grain. Data scattering of SP fracture energy could be explained by combination of microstructural observations and the statistical evaluation method based on the Weibull distribution of SP fracture energy, indicating that brittle inclusions along elongated grain was responsible to the unexpected initial failure type fracture mode.