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

In order to enhance Young’s modulus and strength of titanium alloys, titanium matrix composites with interconnected microstructure were designed based on Hashin-Shtrickmen theory. The results showed that the interconnected microstructure composed of Ti2C particles was achieved through in-situ reaction when the Ti2C content reached 50 vol.%. In the prepared composite, intraparticle Ti lamellae exhibited bimodal size distribution with widths of 10 nm and 230 nm due to precipitation and unreacted Ti phase within grown Ti2C particles. The composites with interconnected microstructure achieved superior properties, including a Young’s modulus of 174.3 GPa and an ultimate flexural strength of 1014 GPa. Compared with pure Ti, the Young’s modulus was increased by 55% because of high Ti2C content and the interconnected microstructure. The outstanding strength was mainly attributed to the strong interfacial bonding, load-bearing capacity of interconnected Ti2C particles, and bimodal intraparticle Ti lamellae that minimized the average crack driving force. Interrupted flexural tests revealed that cracks preferentially initiated along {001} cleavage plane and grain boundary of Ti2C in the region with the highest tensile stress, while the propagation can be efficiently inhibited by interparticle Ti grains, preventing the composites from brittle fracture.