Hot deformation behavior and processing map of a superlight dual-phase Mg-Li alloy

Hot deformation behavior of a superlight dual phase Mg-9Li-3Al-2Y alloy was investigated by developing constitutive equations and constructing processing maps. Constitutive relationship was established by the prediction of materials constants (α, β, n, Q and lnA) based on true stress-strain curves. Processing maps were constructed for Mg-9Li-3Al-2Y alloy based on dynamic materials model (DMM). The instability domains occurred over a narrow temperature range of 423-450 K and strain rate range of 0.01-1s−1, and over a temperature range of 560-573 K and close to strain rate of 1s−1. The twinning in ɑ-Mg phase and cracks in the matrix were observed in the instability domains, the refined dynamic recrystallization (DRX) grains were formed in the regions with high efficiency values. It is undesirable to deform at high strain rates for mechanical properties because of the instability. Dynamic recrystallization occurs first in β-Li phases, and the Al2Y particles were conducive to the DRX process with particle stimulated nucleation effect. The DRX process of ɑ-Mg phase was retarded by β-Li phase. The DRXed grains of β-Li phase showed a random texture, while the basal poles of ɑ-Mg phase rotated towards the normal direction, which can enhance the further deformation. Based on constitutive relationship, processing map and texture evolution, the Mg-9Li-3Al-2Y alloy is easy to suffer from deformation at a wide range of temperatures and strain rates.