Ultrafine-grained magnesium-lithium alloy processed by high-pressure torsion: Low-temperature superplasticity and potential for hydroforming

A Mg-Li alloy with 8 wt% Li was processed by severe plastic deformation (SPD) through the process of high-pressure torsion (HPT) to achieve ultrafine grains with an average grain size of similar to 500 nm. Tensile testing with an initial strain rate of 10(-3) s(-1) showed that the alloy exhibited superplasticity at a temperature of 323 K or higher. Tensile testing in boiling water confirmed that the specimens were elongated to 350-480% at 373 K under the initial strain rates of 10(-3) s(-1) to (1)0(-2) s(-1) with a strain rate sensitivity of similar to 0.3. The current study suggests that not only superplastic forming but also superplastic hydroforming should be feasible after the grain refinement using the HPT method. (C) 2015 Elsevier B.V. All rights reserved.