Effect of twins and dynamic recrystallization on the microstructures and mechanical properties of Ti/Al/Mg laminates

Abstract

Ti/Al/Mg laminates were fabricated by hot rolling at 450 °C and annealed at 200 °C and 300 °C for 1 h. Both Mg/Al and Ti/Al interfaces are well-bonded, without cracks or pores. The results indicate that mechanical properties of laminate largely depends on the microstructure of Mg layer. Rolled laminate stretched along rolling direction (RR) shows excellent ultimate tensile strength of 580 MPa and elongation of 38%, resulting from dynamic recrystallization (DRX) of Mg grains near Mg/Al interface and twinning far away from Mg/Al interface. Abundant twins and DRX subdivide coarse Mg grains, and grain refinement is beneficial to strength and plasticity. Meanwhile, twins hinder dislocation motion and promote coordinated deformation by changing grains from hard orientation to soft orientation, which also improves the strength and plasticity. When RR is annealed at 200 °C for 1 h, extensive static recrystallization which prefers to nuclei at twin intersections occurs in Mg layer, and percentage of high angle grain boundaries and average value of Schmid factor of {11¯00} and {112¯2} slips increase, weakening basal texture and enhancing ductility. For RD samples, yielding and fracture first occur in Mg layer and then in Ti layer, and delamination starts from the Mg/Al interface, which is not found in TD samples. Keywords: Ti/Al/Mg laminates, Interface, Twin, DRX, Texture, Mechanical properties