Effect of High-Temperature Normalizing Heat Treatment on Interfacial Microstructure and Mechanical Properties of Rolled Titanium Steel Composite Plate

To study the effect of high-temperature environment on the properties of titanium steel composite plate, the normalized heat treatment of rolled titanium steel composite plate was carried out at 800-1000 °C for 1 h in this work. Then, the microstructure and element diffusion of the bonding interface were studied by various microscopic instruments. Furthermore, the mechanical properties of the bonding interface of the composite plate were tested by hardness test and shear tensile test. The results demonstrated that the normalizing process greatly enhances the interatomic diffusion and microstructure transformation at the bonding interface. With the increase in temperature, a new microstructure appeared on the titanium side of the bonding interface, and the average grain size of the steel side increased. TiC was formed at the interface at 900 °C and partially dissolved at 950 °C. After the partial melting of TiC in the interface reaction layer, the element diffusion accelerated and the content of Ti/Fe series intermetallic compounds increased, which improved the microhardness at the interface and significantly reduced the interfacial shear strength. The morphology of the peeled surface of titanium steel was characterized by microcracks, cleavage surfaces and pits, mainly brittle fracture, and some areas were ductile fracture.