Interfacial complex reactions and microstructures in vacuum hot-rolling bonded titanium-steel clad composites dominated by bonding temperature

Abstract

Vacuum hot-rolling bonded (VHRB) titanium-steel clad composites with high performance are extensively required by both corrosion-resistant and load resistant equipment, and their high interfacial bonding strength strongly depends on an improved microstructure of interfacial reaction layer. This requires continuous exploration of a new solution. For this attempt, VHRB Ti/steel composites were prepared by hot-compression bonding on a thermal-mechanical simulator at two temperatures of 850 °C and 890 °C for typical α-Ti and β-Ti phase domains, respectively, and their interfacial reaction and products were explored mainly via transmission electron microscope (TEM). It was found that with the bonding temperature decreased from 890 to 850 °C, the interfacial multilayer microstructure of TiFe2+TiC (RLi)-TiFe (RLii)-TiC (RLiii) from the steel side to the Ti side of composites was replaced by that of TiFe2+TiC (RLI)-TiC (RLII)-TiFe (RLIII), due to their different competitive diffusion of C, Fe, and Ti atoms and diffusion barrier playing by TiC. In addition, the average thickness of the brittle interface reaction layer decreased from 0.87 to 0.64 μm, while the average thickness of corresponding sublayer changed from 0.30 μm (RLi)-0.27 μm (RLii)-0.30 μm (RLiii) to 0.22 μm (RLI)-0.28 μm (RLII)-0.14 μm (RLIII). This contributed to the increase of interfacial bonding strength from 235 to 410 MPa.