Abstract
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 × 10~(-4) s~(-1). Flow stress curves and microstructural examination showed that continuous dynamic re-crystallization 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× 10~(-4) s~(-1) and at 573,603 and 633 K at a strain rate of 1.67 × 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 × 10~(13) m~(-2), and the number of dislocations was 59 at 633 K and 1.67 × 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.
NSTL
Elsevier