Variation of High-Pressure Torsion Processing Modes for Fabrication of the Hybrid Al–Nb System

In this paper, we study a composite material of the hybrid Al–Nb system fabricated by the method of severe plastic deformation by high-pressure torsion (HPT) up to 30 revolutions. To obtain a composite material, a three-layer Al–Nb–Al stack was subjected to deformation at room temperature on Bridgman anvils under a pressure of 5 GPa at N = 10, 25, and 30 revolutions and a deformation rate of ω = 1 and 2 rpm. The initial diameters of the pure aluminum and niobium disks, as well as the HPT conditions for the formation of monolithic and defect-free composite samples, were selected experimentally. The most intense crushing and mixing of niobium in aluminum occurred at an aluminum disk diameter of 10 mm and deformation conditions of N = 25 and 30 revolutions and ω = 2 rpm. After HPT under optimal conditions, three microstructural zones were observed in the samples: a central zone with wide curved niobium layers in aluminum, a zone in the middle of the radius with a finely dispersed banded structure, and a zone with a uniform distribution of niobium in an aluminum matrix at the periphery of the sample. The HPT was shown to lead to the formation of the Al3Nb intermetallic phase. The microhardness along the diameter of the obtained composite samples changed nonmonotonically and depended on the formed structure (microstructural zone).