High strain rate superplasticity in an Al-Li-Mg alloy subjected to equal-channel angular extrusion

Abstract

The superplastic behavior of an Al-4.1%Mg-2.0%Li-0.16%Sc-0.07%Zr alloy (1421 Al) subjected to intense plastic straining by equal-channel angular extrusion (ECAE) was studied in the temperature interval 250-450°C at strain rates ranging from 1.4 × 10-5 to 1.4 s-1. The grain size after ECAE was about 0.8 μm and the fraction of high angle boundaries was about 80 pct. The highest elongation of 1850% without failure appeared at a temperature of 400°C and initial strain rate of 1.4 × 10-2 s-1 with corresponding coefficient of the strain rate sensitivity of 0.6. It was shown that the ECAE processed 1421 Al exhibits superior superplastic properties in the temperature range 300-450°C with the strain rate sensitivity higher than 0.4. Microstructural evolution and cavitation during high strain rate superplastic deformation were examined.