MANIFESTATION OF SUPERPLASTICITY AT LOWER TEMPERATURES OF 1565CH ALLOY OF THE Al−Mg SYSTEM IN ULTRAFINE-GRAIN AND NANOSTRUCTURAL STATES

Abstract

In this work, homogeneous nanostructured and ultrafine-grained (NS and UFG) states with an average grain size of 95 nm and 200 nm, respectively, are formed in the 1565ch alloy of the Al-Mg system. In both states, the microstructure is formed by a network of predominantly high-angle grain boundaries. It has been shown that an alloy with an NS and UFG structure formed at room temperature by high-pressure torsion (HPT) and at 200°C by equal-channel angular pressing according to the Conform scheme (ECAP-С) exhibits similar signs of superplastic (SP) behavior at low temperatures 250 …300 °С in the range of strain rates 5×10-4 s-1…10-2 s-1: elongation values were 170…560%, the rate sensitivity coefficient (m) was 0.3-0.73 at low flow stresses . The temperature range of stability of the strength characteristics of the 1565ch alloy in the NS and UFG states was established, both after thermal and deformation-thermal treatment. It is shown that the material in both studied structural states retains a high level of strength after deformation under SP conditions. The deformation relief formed on the working part of the NS and UFG samples of the 1565ch alloy at the stage of a steady-state SP flow is analyzed.