Interconnected microstructure and flexural behavior of Ti2C-Ti composites with superior Young's modulus

To enhance the Young's modulus (E) and strength of titanium alloys, we designed titanium matrix composites with interconnected microstructure based on the Hashin-Shtrikman theory. According to the results, the in-situ reaction yielded an interconnected microstructure composed of Ti2C particles when the Ti2C content reached 50vol%. With widths of 10 and 230 nm, the intraparticle Ti lamellae in the prepared composite exhibited a bimodal size distribution due to precipitation and the unreacted Ti phase within the grown Ti2C particles. The composites with interconnected microstructure attained superior properties, including E of 174.3 GPa and ultimate flexural strength of 1014 GPa. Compared with that of pure Ti, the E of the composite was increased by 55% due to the high Ti2C content and interconnected microstructure. The outstanding strength resulted from the strong interfacial bonding, load-bearing capacity of interconnected Ti2C particles, and bimodal intraparticle Ti lamellae, which minimized the average crack driving force. Interrupted flexural tests revealed preferential crack initiation along the {001} cleavage plane and grain boundary of Ti2C in the region with the highest tensile stress. In addition, the propagation can be efficiently inhibited by interparticle Ti grains, which prevented the brittle fracture of the composites.