Microstructure characterization and mechanical properties of TiB₂/TiAl in situ composite by induction skull melting process

Microstructures and mechanical properties of Ti-45Al-2Nb-1.5V-1Mo-0.3Y+3vol% TiB₂ in situ composite fabricated by induction skull melting (ISM) process were investigated. Results showed that ISM process is feasible to fabricate high-quality in situ TiB₂/TiAl composite. The composite exhibits much finer lamellar colony size and lamellar spacing, compared with its TiAl base. Hexagonal primary and needlelike second TiB₂ particles uniformly distribute mainly near lamellar colony boundaries with a few inside lamellar colonies. TiB₂ crystals in current TiAl composite exhibit faceted growth mode along [0001] direction. The diverse morphologies of TiB₂ are principally ascribed to intrinsic crystal structure and different growth stages during solidification. This composite exhibits much better tensile strength and ductility than its TiAl matrix, with tensile strength (UTS) 610MPa and elongation (e{open}) 0.7% at room temperature, and UTS 505MPa and e{open} 12% at 800°C, respectively.