Effect of different TiNi/Ti2Ni ratios on the compressive properties and toughening mechanisms of biomimetic brick-and-mortar structural composites

• SPS and hot rolling successfully fabricated BMS-ICMs with varied soft/hard ratios. • 3D interlocking TiNi/Ti 2 Ni interface formation for substantially enhanced bonding. • The 0.03Ti BMS-ICM (71 vol% TiNi) achieves a balance of strength and toughness. • Crack deflection and bridging in BMS suppress delamination observed in ICM. The classic brick-and-mortar structure (BMS) of nacre has provided significant inspiration for the design of composites. Although conventional laminated materials adopt a similar hard/soft alternating configuration, they are limited to two-dimensional planar bonding. In this study, we developed a BMS intermetallic composite material (BMS-ICM) with different TiNi (mortar)/Ti 2 Ni (brick) ratios via spark plasma sintering combined with hot rolling. This process enables the formation of a three-dimensional interlocking effect between the rigid “bricks” and the ductile “mortar” at the interface, which significantly enhances interfacial strength and stress transfer. Through the investigation of the microstructure and mechanical properties of BMS-ICM, it was found that the compressive strength was higher when loaded along the transverse direction-rolling direction (TD-RD) plane than the other two planes. The 0.03 mm thick Ti foil (0.03Ti) BMS-ICM demonstrated optimal properties, achieving a compressive strength of ∼ 1771 MPa and a fracture strain of ∼ 23.45 %. Its larger brick spacing effectively suppresses delamination and crack propagation, thereby enhancing toughness. Compared to ICM, the unique structure of the BMS-ICM provides a hybrid toughening mechanism, including crack deflection and bridging. Therefore, by adjusting the appropriate TiNi/Ti 2 Ni ratio, the comprehensive mechanical properties of BMS-ICM can be further enhanced.