Superplasticity in Mg–Li–Zn Alloys Processed by High Ratio Extrusion

Abstract

Abstract Superplastic behavior of Mg-8.5Li-1Zn and Mg-8.5Li-3Zn alloys has been investigated. Dynamic recrystallization occurs in the Mg–Li–Zn alloys during extruding with high ratio after stir casting. Mg-8.5Li-1Zn alloy exhibits an elongation of about 400% at the high strain rate of 1.1 × 10−2 S−1 at 623 K, while the Mg-8.5Li-3Zn alloy shows maximum elongation of more than 540%. The apparent activation energy for superplastic flow of both Mg-8.5Li-1Zn and Mg-8.5Li-3Zn alloys at 573–673 K is about 86 kJ/mol and 79 kJ/mol, respectively, so that the dominant deformation mechanism in Mg–Li–Zn alloys is grain boundary sliding (GBS) controlled by grain boundary diffusion. Keywords: Activation energyElongationExtrusionFractureGrain boundaryMagnesium alloysMagnesium–lithium alloyMetallographic phasesPlastic flowRecrystallizationSlidingStirring castingStrain rateSuperplasticityTensile testing ACKNOWLEDGMENT One of the authors (Shangli Dong) gratefully appreciates the financial support from Japan Society for the Promotion of Science (JSPS).