Effect of tempering temperature on the microstructure and mechanical properties of Ti-6Al-4V/EH690 clad plates with stainless steel interlayer by vacuum hot rolling

Abstract

Titanium (Ti)/steel clad plates have demonstrated significant potential for advancing marine engineering applications by leveraging the advantages of both materials. This study investigated the impact of tempering temperature on the microstructure and mechanical properties of Ti-6Al-4V/EH690 clad plates with stainless steel (SS) interlayer produced by vacuum hot rolling, elucidating the microstructural evolution and formation mechanisms at the interface. The results revealed that the addition of the SS interlayer leads to the formation of two distinct layers of intermetallic compounds (IMCs) observed through scanning transmission electron microscopy (STEM): layer 1, located near the SS interlayer, comprised of TiC, Fe₂Ti, and σ phase, while layer 2, adjacent to the Ti-6Al-4V side, was composed of FeTi. The incorporation of the SS interlayer reduced the microhardness differential across the interface, thereby enhancing the shear strength. After tempering at 560 °C, the clad plate exhibited the highest shear of 256 MPa. Shear fractures at different tempering temperatures occurred at the Ti-6Al-4V/SS interlayer interface, exhibiting a ductile-brittle mixed fracture mode. As the tempering temperature increased, the decarburization of EH690 steel intensified, resulting in an increase in brittle TiC within the interface IMCs layer and a corresponding decline in shear strength. The clad plates displayed delamination fracture characteristics during tensile testing. As the tempering temperature increased, the recrystallization softening of the base and cladding materials delayed interface delamination, resulting in a peak elongation (EL) of 20.5 % after tempering at 660 °C. By controlling the tempering temperature, the distribution of interfacial products in Ti-6Al-4V/EH690 clad plates with an SS interlayer could be precisely tailored, strengthening interfacial bonding and improving the synergistic deformation capability of the base and clad materials.