Strength-ductility matching of hot-rolled pure titanium/ pure magnesium/magnesium alloy laminated composite plates regulated by low-temperature annealing

Titanium/magnesium laminated composites combine the high strength and corrosion resistance of titanium with the low density of magnesium, offering broad application prospects. In this study, a pure Mg interlayer was introduced to form an oxygen-containing interfacial transition zone between TA1 commercially pure titanium and AZ31 magnesium alloy, thereby avoiding the formation of brittle intermetallic compounds and using the plasticity of pure Mg to accommodate the deformation mismatch between pure titanium and the magnesium alloy, so as to improve the strength–ductility matching of Ti/Mg composite plates. The composite plates were hot rolled at 400 °C with a 35% reduction and subsequently annealed at 200 °C for 60, 120, and 180 min. The results show that the as-rolled composite plate had an ultimate tensile strength (UTS) of 355.55 MPa, an elongation of 9.7%, and a TA1/Mg interfacial tensile-shear strength of 83.7 MPa; after annealing for 180 min, the UTS increased to 366.67 MPa and the elongation increased to 20.3%, whereas the interfacial shear strength decreased to 71.0 MPa. Digital image correlation results indicate that crack initiation was governed by shear localization rather than axial tensile instability: the peak in-plane shear strain on the Mg side before fracture decreased from 0.1616 in the as-rolled state to 0.0397 after annealing for 180 min. Annealing promoted recrystallization on the Mg side and suppressed local shear concentration, thereby delaying crack initiation to a higher global strain, while twinning in the TA1 layer partially compensated for the strength loss. Although the decrease in interfacial strength weakened the interlayer load-transfer efficiency, it did not directly control fracture, and no interfacial delamination was observed. Therefore, by introducing a pure Mg interlayer to join pure titanium and the magnesium alloy and applying an optimized annealing process, a simultaneous improvement in strength and ductility can be achieved.