Microstructures, hot tensile deformation behavior and constitutive modeling in a superlight Mg-2.76Li-3Al-2.6Zn-0.39Y alloy

To explore the ductility and deformation nature, a new Mg-2.76Li-3Al-2.6Zn-0.39Y alloy has been successfully fabricated by decreasing-temperature multidirectional forging and hot rolling. The maximum elongation to failure of 223.0% was demonstrated in this alloy at a temperature of 633 K and a strain rate of 1.67 x 10(-4) s(-1). Flow stress curves and microstructural examination showed that continuous dynamic recrystallization occurred in this alloy at different temperatures and strain rates in most cases, but the flow hardening phenomena appeared at a temperature of 603 K at a strain rate of 5 x 10(-4) s(-1) and at 573, 603 and 633 K at a strain rate of 1.67 x 10(-4) s(-1). A criterion of grain size changing rate was proposed to judge the occurrence of microstructural evolution mechanisms. A modified Johnson-Cook constitutive model established in this alloy was incorporated into dislocation models to realize the estimation of the dislocation density and the number of dislocations under specific conditions. A power-law constitutive equation was established in this alloy. The relationship between average grain size and Zener-Hollomon parameter was established. It was found that the stress exponent was 3.26, and the average experimental activation energy for deformation was 143.67 kJ/mol; the dislocation density was 3.25 x 10(13) m(-2), and the number of dislocations was 59 at 633 K and 1.67 x 10(-4) s(-1). All of these results indicate that the predominant deformation mechanism of this alloy under this condition is dislocation glide creep controlled by lattice diffusion. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

A new Mg-2.76Li-3Al-2.6Zn-0.39Y alloy was successfully fabricated and exhibited maximum elongation to failure at 633K and 1.67 x 10(-4) s(-1) strain rate, with a predominant deformation mechanism of dislocation glide creep controlled by lattice diffusion. Flow stress curves and microstructural examination revealed continuous dynamic recrystallization in most cases, but flow hardening phenomena at specific temperatures and strain rates.