Effects of Zr/(Sc+Zr) microalloying on dynamic recrystallization, dislocation density and hot workability of Al−Mg alloys during hot compression deformation

Abstract

The deformation behavior and microstructure characteristics of Al−6.00Mg, Al−6.00Mg−0.10Zr and Al−6.00Mg−0.25Sc−0.10Zr (wt.%) alloys were investigated by hot compression tests and electron microscopy methods. The results show that after deforming under the maximum processing efficiency condition (673 K, 0.01 s−1), dislocation densities of Al−6.00Mg, Al−6.00Mg−0.10Zr and Al−6.00Mg−0.25Sc−0.10Zr alloys are 2.68×1016, 8.93×1016 and 6.1×1017 m−2 respectively. Their dynamic recrystallization fractions are 19.8%, 15.0% and 12.7%, respectively. Kernel average misorientation (KAM) analyses indicate that dislocation accumulation near grain boundaries is enhanced by adding Zr or Sc+Zr. Besides, the established hot processing maps, based on the dynamic material model (DMM), reveal that the addition of Zr or Sc+Zr can reduce the range of low-temperature unstable domain but expand the unstable domain at high temperatures and high strains. The experimental results further verify that under the testing deformation condition, only the Al−6.00Mg−0.25Sc−0.10Zr alloy cracks at 773 K and 1s−1.