Study on Microstructure and Properties of Additive-Manufactured TC4ELI+TC21 Titanium Alloy Gradient Composite Structures

TC4ELI+TC21 titanium gradient composite structures with direct transition (TD1) and cross transition (TD2) were prepared using laser deposition manufacturing technology. The microstructure of the gradient interface was observed, and the distribution of alloying elements was detected. The tensile properties of the two alloys at room temperature were tested, and the effects of different heat treatment regimens on the microstructure and mechanical properties were investigated. The results show that there is no obvious defect at the gradient interface of the two alloys. Compared with direct transition alloys, the alloying elements of TD2 alloys change less at the interface, the structure of the transition zone is more closely bound, and the elongation is higher. After heat treatment, the α phase in the alloy is coarsened, and the alloy elements at the interface are fully diffused, so that the gradient interface of the alloy is eliminated to a certain extent, the tensile strength of the alloy decreases, and elongation increases. The strength and plasticity of the alloy reached their best match at a solution temperature of 930 °C.