Low-Temperature Superplasticity of the 1565ch Al–Mg Alloy in Ultrafine-Grained and Nanostructured States

Abstract

—Homogeneous nanostructured and ultrafine grained (NS, UFG) states with mean grain sizes of 95 and 200 nm, respectively, have been formed in a 1565ch Al–Mg alloy (Al–5.66Mg–0.81Mn–0.67Zn–0.09Zr–0.07Cr–0.04Ti–0.001Be–0.3(Fe + Si) wt %). Microstructure of both states is represented by grain boundaries with predominantly high-angle misorientations. The alloy, produced both by high pressure torsion at room temperature and equal channel angular pressing at 200°C using the Conform approach, exhibits superplasticity at low temperatures in the range 250–300°C and strain rates in the range of 5 × 10–4–10–2 s–1. Elongation values range 170–560%, while the rate sensitivity coefficient (m) varies from 0.3 to 0.73 at low flow stress for both NS and UFG structures. The temperature range for the stability of strength properties of the 1565ch alloy in NS and UFG states after thermal and thermal mechanical treatments has been determined. The material in both structural states maintains a high level of strength after undergoing deformation under SP conditions. The deformation relief formed on the gage surface of the NS and UFG specimens of the 1565ch alloy during the established SP yield stage has been analyzed.