Mechanical Properties of a High-Purity Fe–9Cr–2W–0.1C Model Alloy for Low-Activation Ferritic Steels for Fusion Reactors

Abstract

Reduced-activation ferritic steels, such as JLF-1 (Fe-9Cr-2W-0.1C--V-Ta-N) steel, are candidate structural materials for use in the next fusion device. It is essential to develop low-activation ferritic steels which have been purified in order to reduce the amount of radioactive impurity elements. It is important to clarify whether or not purification causes any significant changes in the mechanical properties of the ferritic steels, as they will be used as structural materials. In this study a high-purity Fe-9Cr-2W-0.1C model alloy was prepared from an ultra-high-purity iron. A significantly lower tensile strength was observed in the high-purity ferritic steel at room temperature and 573 K, as compared to that of JLF-1 steel. The difference in yield strength at room temperature is considered to be mainly due to a lower content of nitrogen and soluble impurities, a larger packet diameter and a larger lath length in the case of the high-purity steel. The hardness of the as-quenched high-purity steel and the recovery behavior below 823 K are not significantly different from those of conventional ferritic steel.