Effect of annealing on the microstructures and mechanical properties of Al/Mg/Al laminates

Abstract

Al/Mg/Al laminates were fabricated by hot rolling at 400 °C and annealed at temperature ranging from 200 °C to 400 °C for 1 h to 4 h. Microstructural examination revealed that brittle intermetallics identified as Mg17Al12 and Al3Mg2 appeared at Mg/Al interface when annealing temperature exceeded 300 °C. Al layers in laminates annealed at 200 °C exhibited typical copper-type texture, which totally transformed to recrystallized cube texture at 400 °C with a higher intensity. Mg layers in annealed laminates presented (0002) basal texture with c-axis titling from normal direction (ND) to rolling direction (RD), and bimodal basal texture was observed at 400 °C. Recrystallization extent of Mg layer increased with the increase in annealing temperature and/or annealing time, and nuclei preferred to occur in grains near Mg/Al interface. Grain size, texture type of matrix, and thickness of intermetallic layers all influence mechanical properties of Al/Mg/Al laminates. Laminates annealed at 200 °C for 1–4 h exhibited better ultimate tensile strength (UTS) ranging from 223 MPa to 240 MPa and elongation (EL) ranging from 21% to 26%. Despite more extensive recrystallization of laminate annealed at 400 °C, thicker intermetallics greatly decreased its strength and plasticity because crack initials and quickly propagates along Mg/Al interface or in the interior of intermetallics.