Hardness Evolution and Deformation Behavior of Tungsten and Doped Tungsten Fine Wires

The increasing demand for highly specialized advanced materials requires a comprehensive understanding of the relationship between processing conditions and the resulting mechanical properties. This study investigates the structure-property relationship of pure tungsten and potassium-doped tungsten fine wires, focusing on material hardness as a function of deformation state and annealing treatment. Hardness was evaluated using nanoindentation and microhardness testing, respectively. The results show a monotonic increase in hardness with increasing amount of deformation, with pure tungsten exhibiting slightly higher hardness than potassium-doped tungsten except at the highest deformation levels. The measured hardness ranged from approximately 13 GPa to 15 GPa depending on the deformation condition. Recovery annealing (400–500°C) led to further increases in hardness, indicating annealing-induced hardening effects. In contrast, high-temperature annealing up to 2400°C resulted in grain growth from approximately 100 nm to 500 nm and a corresponding decrease in hardness for potassium-doped tungsten, from approximately 8.5 to 4.5 GPa. The findings demonstrate the combined influence of deformation and thermal treatment on hardness evolution in tungsten fine wires and provide insight into microstructure-dependent strengthening mechanisms.