Microstructure regulation and strengthening-toughening mechanism of TiAl matrix composites synergistically reinforced by TiB₂/Ti₂AlC multiphases

Ti48Al2Cr2Nb-0.5GO-xTiB₂ (x is mass fraction/%) composites synergistically reinforced by TiB₂ and Ti₂AlC are fabricated via spark plasma sintering. The effects of TiB₂ content on the microstructural evolution and mechanical properties of the composites at room and high temperatures are systematically investigated. The results reveal that the addition of TiB₂ significantly refines the lamellar colony size and promotes the transformation of the matrix microstructure from fully lamellar to duplex microstructure, which effectively improves the microstructural homogeneity of the material. The composite with 0.3%TiB₂ exhibits optimal comprehensive mechanical properties, with a compressive strength of 1870 MPa and compressive strain of 27.5% at room temperature, respectively. When the TiB₂ content is 0.2%, the high-temperature tensile strength at 850 ℃ is approximately 500 MPa, representing a 32.5% improvement compared with the base alloy. Micromechanical analysis demonstrates that the enhanced performance mainly originates from grain refinement strengthening and second-phase strengthening jointly induced by TiB₂ and Ti₂AlC. During deformation, the reinforcing phases cooperatively regulate plastic deformation behavior and fracture processes through mechanisms including microcrack deflection, interfacial debonding, and stress redistribution, thus optimizing the strength-ductility balance of the material.