High-Performance β-Stabilized Titanium Matrix Functionally Graded Materials with Gradient In-Situ TiB Reinforcement: Mechanical Properties and Fracture Behavior

Abstract Titanium matrix functionally graded materials (FGMs) reinforced with in-situ TiB are promising for aerospace, automotive, defense, and biomedical applications due to their high specific strength, stiffness, wear resistance, and thermal stability. The graded architecture mitigates ceramic brittleness by combining a ductile metallic core with a hard ceramic-rich surface. While Ti-TiB FGMs based on pure Ti or conventional alloys have been widely studied, the incorporation of ß-stabilizing elements (Mo or Fe) in a 0-60 vol% TiB gradient produced by vacuum hot pressing remains largely unexplored, creating a gap in understanding effects on densification, hardness gradient, and mechanical performance. The objective was to fabricate novel ß-stabilized Ti-based FGMs (15-30 wt% Mo or 5-10 wt% Fe) with controlled in-situ TiB gradients (0-60 vol%) via vacuum hot pressing and evaluate their density, hardness, flexural, and compressive properties. Ti, TiB2, Mo, and Fe powders were wet ball-milled, assembled into multilayer stacks, and sintered at 1250 °C under 32 MPa in vacuum. Relative density was determined by Archimedes' principle, Vickers hardness measured layer-wise, flexural strength tested via SENB (ASTM E1820), compressive strength per ASTM standards, and fracture surfaces examined by SEM. All FGMs achieved high relative densities (94.33-98.10%). Maximum Vickers hardness reached 1076.4 HV in the (Ti-10Fe)-60 vol% TiB layer. The (Ti-30Mo) FGM delivered the highest flexural strength (165 MPa), while the (Ti-10Fe) FGM recorded the highest compressive strength (1768 MPa). These ß-stabilized Ti-TiB FGMs exhibit excellent hardness and strength, showing strong potential for turbine components, armor, and implants. The findings guide selection of Mo (for flexural loading) or Fe (for compressive loading) stabilizers.