Microstructure and properties of a beta-solidifying TiAl-based alloy with different refiners

This study systematically compared the influences of yttrium (Y), boron (B), and carbon (C) on the microstructural refinement and properties of a Ti-43Al-5Nb alloy. The microstructural refinement effect in the TiAl alloy closely depends on the refiner used. The refinement effects of the three elements on colony size and lamellar thickness can be arranged as B > Y > C and Y > C > B, respectively. Moreover, a microstructure with a small grain size and ultra-fine lamellar spacing can be obtained by adding B and Y or B and C. The mechanical properties of TiAl alloy are also influenced by the refiners. TiAl alloys with proper B and Y contents exhibit favorable hot workability, tensile properties, and fracture toughness, whereas the C-containing alloy displays poor tensile properties and low fracture toughness. These results indicate that Y and B are more suitable microstructure refiners than C. This study may serve as a reference for practical alloying design.