Effect of torsion conditions under high pressure on the structure and strengthening of the Zr-1% Nb alloy

The effect of temperature and degree of deformation upon severe plastic deformation by torsion under a high pressure on the structure, phase composition, and microhardness of the industrial zirconium Zr-1% Nb alloy (E110) has been studied. The high-pressure torsion (HPT) (with N = 10 revolutions) of the Zr-1% Nb alloy at room temperature results in the formation of grain-subgrain nanosize structure with an average size of structural elements of 65 nm, increase in the microhardness by 2.3-2.8 times (to 358 MPa), and alpha-Zr -> beta-Zr and alpha-Zr -> omega-Zr phase transformations. The increase in the HPT temperature to 200A degrees C does not lead to a decrease in the microhardness of alloy owing to the increase in the fraction of omega-Zr phase, though the average size of structural elements increases to 125 nm. The increase in the temperature to 400A degrees C during HPT with N = 10 revolutions leads to the grain growth in the alpha-Zr grain structure (similar to 90%) to 160 nm and a decrease in the microhardness to 253-276 HV.