Reduction-Rate-Dependent Interfacial Evolution and Bonding Strength of Gleeble-Simulated Ti/Steel Composites

Titanium/steel composites were fabricated by Gleeble-simulated vacuum hot bonding with reduction rates of 50%, 60%, 70%, and 80% to clarify the effect of deformation on interfacial microstructure and bonding strength. The results show that interfacial bonding strongly depends on the reduction rate. Residual voids were observed at 50% reduction, whereas continuous metallurgical bonding was achieved at approximately 60% reduction under the present processing conditions. The interface exhibited a multilayer reaction structure composed mainly of TiC and Ti–Fe intermetallic compounds. With increasing reduction rate, the interfacial structure evolved from a four-layer configuration to a three-layer configuration, accompanied by the fragmentation and discontinuity of the coarse TiC-rich layer near the Ti side. The bonding strength increased progressively with increasing reduction rate and reached 376 MPa at 80% reduction. These results reveal that the reduction rate controls the transition from interfacial void closure to reaction-layer refinement in Gleeble-simulated vacuum hot-bonded titanium/steel composites.