Observations on the Ductility and Thermostability of Tungsten Processed from Micropowder by Improved High-pressure Torsion

Tungsten was subjected to severe plastic deformation at 440 °C using high pressure torsion (HPT) with an improved die-set. Microhardness measurements suggest an appreciable ductility level in tungsten after HPT with Vickers microhardness HV as high as ∼11 500 MPa. Differential scanning calorimetry (DSC) analyses show that samples with less strain have a higher recrystallisation temperature (greater than 1450 °C) than samples with more strain (∼800 °C). X-ray diffraction analyses indicate increases in lattice strain up to 0.35%, lattice parameter up to 0.3177 nm and dislocation density up to 2.4 × 1015 m−2. The current study introduces the improved HPT process as an effective route for the production of ultrahigh strength W with significant ductility and specified thermostability