Microscale Investigation on the Monotonic Tension and Fatigue Deformation-Failure Mechanisms of TiC/Ti6Al4V Composites

The microstructure where compositions interact with each other dominates the macroscopic properties of composites, but microscale deformation-failure mechanisms especially under fatigue remain unclear. Herein, the deformation-failure mechanisms of TiC/Ti6Al4V composites with three reinforcement volume fractions are investigated. Under monotonic tension, increased reinforcement content enhances yield strength and Young's modulus but reduces tensile strength due to reinforcement failure in the later stage, leaving the matrix as the primary load-bearing component. Dislocation density increases continuously and monotonously, dominated by Shockley dislocations, with subsequent length reduction attributed to the Orowan mechanism. Under cyclic tensile loading, composites with higher reinforcement content gradually exhibit cyclic hardening, while they show cyclic softening under cyclic compression even in early cycles due to back stress effect. Dislocation sources cause uneven distribution and repeated multiplication of dislocations. Localized atomic stress concentration promotes phase transitions, altering the microstructure and driving crack initiation and propagation.