Evaluation of microstructural and mechanical properties of ARAA plates with various thicknesses

The Advanced Reduced-Activation Alloy (ARAA), developed in Korea as a reduced-activation ferritic/martensitic (RAFM) steel, is designed for structural applications in fusion reactor breeding blankets, where materials are subjected to elevated temperatures and intense neutron irradiation. Given the diverse geometries and thicknesses of structural components, ensuring consistent mechanical reliability across different plate dimensions is critical. This study investigated the microstructural and mechanical properties of ARAA plates with thicknesses of 20, 36, and 62 mm, all fabricated under identical normalizing and tempering conditions. Optical microscopy and EBSD analyses revealed fine, non-elongated prior austenite grains (PAGs) without localized coarsening across all thickness positions and directions. Despite experiencing the lowest thickness reduction, the 62 mm plate retained a refined grain structure throughout the thickness, similar to the 20 mm plate, which underwent the highest deformation. Tensile and impact tests showed consistent strength, ductility, and toughness in all directions, including the short transverse, with no evidence of anisotropy or degradation related to thickness. These results demonstrate that the current ARAA fabrication process enables stable grain morphology and uniform mechanical performance across a thickness range of 20–62 mm, supporting the reliable use of ARAA in fusion blanket structures subjected to multidirectional loading, thermal gradients, and irradiation.