Hot compression deformation behavior of Mg-9Gd-2.9Y-1.9Zn-0.4Zr-0.2Ca (wt%) alloy

Hot deformation behavior of the homogenized and quenched Mg-9Gd-2.9Y-1.9Zn-0.4Zr-0.2Ca (wt%) alloy was investigated by compression test at temperatures of 300 500 C and strain rates of 0.00110 s(-1). The flow stress is sensitive to the deformation temperature and strain rate, which increases with increasing strain rate and decreasing temperature. The processing map constructed at the strain of 0.9 shows two stability domains with high power dissipation efficiencies and the optimum hot working condition for the alloy is determined as deformation temperature of 450 C and strain rate of 0.01 s(-1), which correlates with the continuous dynamic recrystallization as main softening mechanism. However, dense lamellar-shaped long period stacking ordered (LPSO) phases precipitate inside original grains during preheating and deformation, which restrict the dynamic recrystallization. Consequently, dynamic recrystallization proceeds incompletely. Adiabatic shear bands and cracks formed at grain boundaries lead to the premature failure of the samples compressed at strain rate of 10 s(-1) in the instability domain where should be avoided during processing. (C) 2016 Elsevier Inc All rights reserved.