Effect of Grain Structure Anisotropy and Recrystallization on Tensile Properties of Swaged Tungsten Rod

Abstract

Tungsten (W) is considered as primary candidates for plasma-facing materials (PFM) in current fusion reactor designs because of their high melting point and high sputtering resistance. In this study, pure W rods fabricated by a swaging process and having two different diameters (6 and 10 mm) are examined. To investigate the effect of anisotropy and recrystallization on the tensile properties of W rod, grain structure, hardness, tensile strength and elongation, and fracture surfaces are observed or measured for as-received and heat-treated materials. Based on grain structure observation and tensile tests, the axial and radial directions of W rod show different microstructures, called microstructure anisotropy due to swaging. A significant anisotropy of tensile properties is observed in as-received W rods at room temperature. Tensile strength of the rod with smaller diameter is higher than that of the one with larger diameter, and plastic deformation is observed only for the as-received smaller diameter rod, in further measurements at room temperature. However, when tested at 773 K there is no obvious anisotropy of tensile properties observed in as-received and heat-treated materials. Through these comparisons, the smaller diameter rod material shows better tensile properties than the one with larger diameter because of its higher reduction ratio. The reduction ratio plays an important role in affecting the microstructure and tensile properties of W rod material.