Achieving ultrahigh strength in the Ti-6554 alloy via synergistic nanoprecipitates and twinned nanolamellae enabled by thermal-magnetic coupling

The pursuit of ultrahigh strength in titanium alloys remains challenging due to the difficulty of precisely controlling their hierarchical microstructure. Herein, we introduce a thermal-magnetic coupling approach that enables the synergistic control of multiscale structural features in a Ti-6554 alloy. A 0.6 T magnetic field was applied during aging at 350°C - 520°C for 6 h. The microstructural evolution and mechanical properties were systematically explored across the aging series. At 350°C, only micron-sized α laths formed. At 520°C, significant coarsening of secondary α (α s ) occurred. Strikingly, aging at 435°C generated a heterogeneous architecture comprising micron-sized α phase, continuous grain boundary α phase, dense α s nanoprecipitates, and twinned α s nanolamellae. The formation of the twinned α s nanolamellae results from the thermal-magnetic coupling treatment, which markedly accelerates the β→α phase transformation kinetics. It also promotes atomic rearrangement at the interface during the collision and growth of the α s variants. Consequently, an intervariant angle of ∼122° develops between the (0001) planes of adjacent α s variants, ultimately forming low-energy {10 1} α coherent twin boundaries. The resulting alloy exhibited an ultrahigh yield strength of ∼1424.7 MPa, representing increases of ∼46.2% and ∼29.8% over the 350°C- and 520°C-aged counterparts, respectively. The superior mechanical properties arise from the strong hindrance of dislocation motion by the multiscale and high-density α/β interfaces and coherent α s /α s twin boundaries. These findings demonstrate that magnetic field-assisted aging offers a powerful pathway to engineer hierarchical architectures in titanium alloys for superior strength-ductility synergy.