Abstract
High-pressure torsion (HPT) was conducted on pure W powder (99.9wt.%) at the temperature of 713K and the Vickers microhardness along the disk radius was measured. The microstructure and thermal stability after HPT were characterized by X-ray diffraction (XRD) and differential scanning calorimetry (DSC), respectively. The results show that the increasing equivalent strain resulted in grain refinement, microhardness improvement and thermal stability enhancement. The nanostructured W samples with crystallite size of 32.5nm, dislocation density of 9.19×1014m−2 and average microhardness of 1020Hv were obtained through 4GPa and 10 revolutions of HPT. For HPT samples at 2GPa and 5 turns, uniformly distributed nucleation sites around grain boundaries led to the recrystallization temperature increasing. A complex recrystallization mechanism occurred in the sample after 4GPa and 10 turns, including continuous dynamic recrystallization (cDRX) during HPT and continuous static recrystallization (cSRX) during DSC heating.
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