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

Al/Mg/Al laminates were fabricated by hot rolling at 400 degrees C and annealed at temperature ranging from 200 degrees C to 400 degrees 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 degrees C. Al layers in laminates annealed at 200 degrees C exhibited typical copper-type texture, which totally transformed to recrystallized cube texture at 400 degrees 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 degrees 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 degrees 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 degrees 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.