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Neutron irradiation-induced embrittlement of the reactor pressure vessel (RPV) leads to an increase in the transition temperature (T_0) of the RPV steel and reduces the operating lifetime of nuclear reactors. Fracture mechanics testing of RPV steels before and after neutron irradiation, which reveals the shift in T_0, is often limited by the shortage of irradiated material. To solve this, we tested sub-sized 0.16T C(T) specimens manufactured from already tested SE(B) standard Charpy sized specimens using the Master Curve concept. The transferability of fracture mechanics data from small to standard-sized specimens forms an integral part of this study. To simplify the testing procedure, based on statistical data, we studied the impact of the slow stable crack growth censoring criterion of the ASTM E1921-21 standard on the determination of T_0. We also present a statistically based strategy for an optimized test temperature selection. We found that the results from the small specimens are comparable to the standard specimens. RPV steels containing higher Cu and P contents exhibit a higher increase in T_0 after irradiation. We also found that the stable crack growth-censoring criterion did not influence T_0 significantly. Our results demonstrate the validity of small specimen testing and confirm the role of the impurity elements Cu and P in neutron embrittlement. We anticipate further research linking microstructure to the fracture properties of materials before and after neutron irradiation and the optimization of Master Curve testing using the results from our statistical analysis.

The Hall effect is a powerful tool for investigating carrier type and density. For single-band materials, the Hall coefficient is traditionally expressed simply by , where e is the charge of the carrier, and n is the concentration. However, it is well known that in the critical region near a quantum phase transition, as it was demonstrated for cuprates and heavy fermions, the Hall coefficient exhibits strong temperature and doping dependencies, which can not be described by such a simple expression, and the interpretation of the Hall coefficient for Fe-based superconductors is also problematic. Here, we investigate thin films of Ba(Fe₁₋ₓCoₓ)₂As₂ with compressive and tensile in-plane strain in a wide range of Co doping. Such in-plane strain changes the band structure of the compounds, resulting in various shifts of the whole phase diagram as a function of Co doping. We show that the resultant phase diagrams for different strain states can be mapped onto a single phase diagram with the Hall number. This universal plot is attributed to the critical fluctuations in multiband systems near the antiferromagnetic transition, which may suggest a direct link between magnetic and superconducting properties in the BaFe₂As₂ system.