Achieving a balance between strength and ductility of TiN ceramic particles reinforced Ti₂AlNb matrix composite

To overcome the strength-ductility trade-off in Ti₂AlNb matrix composites, in this study, TiN was selected as the reinforcement due to its similar elastic modulus to the matrix and blunted morphology. Results demonstrated that TiN addition significantly refines the grain size and reduces porosity, with 5 wt% TiN achieving a remarkable grain refinement efficiency of 89.1 %. Additionally, the addition of TiN facilitates both the B2→α₂ and B2→O phase transformations, leading to microstructural differentiation. SEM and TEM observations reveal that abundant B2 and minor O phases precipitated around TiN, but no detectable α₂ phase, a phenomenon that correlates with localized Ti enrichment concomitant with depletion of Nb and Al at the TiN/matrix interface, thereby favoring the formation of the B2 phase. Compared to the matrix alloy, TiN/Ti₂AlNb composites exhibit simultaneous improvements in hardness, strength, and ductility. The strengthening and toughening mechanisms were discussed based on microstructural and fractographic analyses. This study provides guidance to design Ti₂AlNb matrix composites with outstanding properties.