Mechanical tensile properties of an Al-Nb composite obtained by deformation of shear under pressure

Abstract

Presented are the results of obtaining a composite of the Al-Nb system using high-pressure torsion on Bridgman anvils with recesses. A “sandwich” of disc billets of aluminum and niobium in the Al-Nb-Al sequence was laid between the anvils. Deformation was carried out at room temperature under a pressure of 5 GPa for 30 revolutions and a speed of 2 rpm. Investigations of the cross-section of the resulting composite showed that crushing and mechanical mixing of niobium in the aluminum matrix took place practically over the entire volume. In the central region of the composite, mixing is weakly expressed due to the low degree of deformation.Mechanical tests of the obtained composite samples were carried out for three states: initial, immediately after deformation; after annealing at 400 °C; after annealing at 600 °C. Conducted mechanical tensile tests for samples cut from the zone corresponding to the middle of the radius of the resulting composite, showed the following values of ultimate strength: for the initial state – 177 MPa; annealed at 400 °C – 337 MPa; annealed at 600 °C – 291 MPa. Fractographic studies have shown that the dispersed Al3Nb phase is clearly visible on the fracture surfaces of both unannealed and annealed samples. Plastic deformation in the composite occurs mainly along the aluminum matrix; niobium is practically not deformed. Strengthening proceeds according to the dispersed mechanism due to the Al3Nb phase formed at the Al/Nb boundaries. The formation of the optimal size of the hardening phase is observed upon annealing at 400 °C.