In-situ observation of fracture behaviors in TiB2p/Al7050 composites with different gradient structure

The study employed the vacuum hot-pressed sintering method to fabricate TiB2p/Al7050 homogeneous composites (HC) and TiB2p/Al7050 functionally gradient materials (FGM), including three-layer conventional FGM (TFGM) and five-layer bionic interleaved FGM (FFGM). The crack-initiation fracture toughness (KIc), crack propagation fracture toughness (KJc), and crack propagation performance were investigated to examine the impact of gradient structure and TiB2p content. The results highlighted the crucial role of TiB2p content in determining the fracture toughness of the three composites. The fracture toughness of HC requires consideration of the synergistic effects of strength and plasticity, while that of FGM is influenced by the combined effects of strength, plasticity, and interlayer synergistic factors. Additionally, the in-situ observation of the crack propagation path revealed a toughening mechanism that contributes to the improved fracture toughness of these composites. This mechanism includes crack deflection, branching, plastic deformation of the matrix, and crack blunting, which consumes the energy required for crack propagation, reduces the stress concentration at the main crack tip, and delays crack propagation. It is worth mentioning that among these composite materials, FFGM demonstrates the highest fracture toughness, with KIc and KJc increasing up to 22.39% and 22.23% above the average, respectively. The excellent performance can be attributed to its highly effective toughening mechanism. Overall, the study provides valuable insights into the design and development of FGM with superior fracture resistance. Hence, these findings can support the development of advanced materials with improved toughness and potential applications in various fields.