Effect of the Ti volume fraction on microstructure and mechanical properties of brick-and-mortar structure Ti/Al3Ti metal-intermetallic laminate composites

The brick-and-mortar biomimetic structure Ti/Al3Ti metal-intermetallic laminate (BMS-MIL) composites were prepared by vacuum hot pressing. BMS-MIL composites with various Ti volume fractions from 45–71% were obtained by controlling the high-temperature diffusion time of Al–Ti. The phase composition of the BMS-MIL composites was analyzed, and the influence of Ti volume fraction on the microstructure was quantitatively characterized. Quasi-static compression and three-point bending tests were carried out to study the mechanical properties and fracture mechanism of the BMS-MIL composites. The results indicated that, in BMS-MIL composites, Al3Ti appears as polygonal platelets, and Ti fills the gaps between the platelets. With decreasing Ti volume fraction, the size of Al3Ti platelets increased, the number of platelets decreased, and the aspect ratio of platelets first increased and then decreased. The decrease of Ti volume fraction leads to the decrease of mechanical properties of composites. However, as a reasonable and efficient material design strategy, the brick-and-mortar structure ensured that the specific strength of the BMS-MIL composites with load perpendicular to the layer remained stable, with specific strength maintained between 345 and 353 kN m/kg. The compression properties with load parallel to the layer are significantly affected by the platelet's aspect ratio. The sample with 65% volume fraction Ti exhibited the optimal strength, specific strength, and failure strain when compressed parallel to the layer, with a strength of 1347.3 MPa, specific strength of 330.2 kN m/kg, and a failure strain of 6.32%.