Interface evolution mechanisms and mechanical properties during diffusion bonding of TC4 and TiB_w/TC4 dissimilar materials

To address interfacial regulation in low-pressure heterogeneous joining of titanium alloys and titanium matrix composites, diffusion bonding experiments were conducted on TC4 alloy and TiB_w/TC4 composites at 930 °C under a low pressure of 10 MPa. The effects of holding time on interfacial microstructure evolution and mechanical properties were investigated. The results show that, under low bonding pressure, interfacial bonding evolves from initial physical contact to a stage governed primarily by atomic diffusion and void healing. With increasing holding time, the interfacial voids gradually shrank and eventually disappeared. Meanwhile, elements such as Al and V diffused across the interface and undergo selective redistribution. This process promoted the β→α_s phase transformation and gradually connected the α and β_t microstructures across both sides of the interface, leading to improved microstructural continuity. During prolonged holding, creep deformation of the surrounding matrix caused some interfacial TiB_w to become partially embedded in the opposite TC4 matrix, improving local interfacial stability and load transfer. The interfacial shear strength increased to 708 MPa after holding for 70 min, approaching the average shear strength of the TC4 alloy. The fracture mechanism changed from rapid brittle propagation dominated by interfacial voids to crack deflection induced by TiB_w reinforcements.