Thin-gauge Ti/steel composite plates prepared by laser-assisted roll bonding process

This study investigated the morphology characteristics and strengthening mechanisms of Ti/steel composite plates manufactured via laser-assisted roll bonding process. The Ti/steel composite plate exhibited a defect-free surface without periodic indentations and achieved metallurgical bonding without interfacial oxidation, even in the absence of a protective atmosphere. Microstructural characterization revealed a dual-gradient architecture on both sides: The steel side featured a gradient transition from lath martensite to ferrite and pearlite with refined grain sizes (~ 2.42 μm to ~ 1.5 μm), while the Ti side consisted entirely of α-Ti with a basal texture, a secondary {10-11} < -23-13 > pyramidal component, and a gradient grain structure (~ 0.80 μm to ~ 0.65 μm). Meanwhile, the interface formed a ~ 1-μm-thick reaction layer exclusively composed of TiC, with no detectable Fe-Ti compounds, due to thermodynamic and kinetic constraints and TiC’s role as a diffusion barrier. The interfacial bonding strength of Ti/steel composite plates is ~ 154 MPa due to the defect-free interface, confined diffusion layer and intermittent TiC distribution. Furthermore, the superior tensile strength of ~ 728 MPa is obtained by the synergistic effects of raw materials with relatively higher strength and the laser-assisted roll bonding process that induces grain refinement and a dual-gradient structure, facilitating geometrically necessary dislocation accumulation and hetero-deformation-induced strengthening. Therefore, the laser-assisted roll bonding process is a promising way to produce the thin-gauge laminate composite plates composing of heterogeneous metals with significant strength differences.