Microstructure and Microhardness Evolution in Pure Molybdenum Processed by High‐Pressure Torsion

Abstract

Molybdenum, a refractory metal with a body-centered cubic lattice, is processed by high-pressure torsion (HPT) at room temperature under an applied pressure of 6.0 GPa and torsional straining from one-half to ten turns. The microstructures are characterized by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM), and measurements are taken of the Vickers microhardness. The results show a gradual evolution of homogeneity in grain size and microhardness with increasing numbers of HPT turns with an average grain size of %690 nm at the sample edge after five turns and a saturation microhardness of %660 Hv. The grain size after ten turns shows a slight decrease at the center, and the microhardness is slightly lower than after five turns due to the occurrence of limited dynamic recovery.