Superplasticity of an aluminum-lithium 1420 alloy in various structural states

The superplasticity of Al-Li-Mg alloy 1420 with a grain size of 0.3–20 μm has been studied in various structural states. A nonlinear dependence of the superplastic elongation on the grain size is revealed. The optimum temperatures and strain rates are determined for nanocrystalline and submicrocrystalline alloys: they have large elongations (1200–1500%), high strain-rate sensitivity coefficients (higher than 0.45), and low activation energies (60–70 kJ/mol). The existence of an optimal grain size for reaching the maximum strain under structural superplasticity conditions is explained using a theoretical model proposed in this work.