Microstructure and properties of fine-grained orthorhombic transformed Ti-25Al-10Nb-3V-1Mo (Super α2) Ti aluminide

The mechanical properties of a titanium aluminide alloy with the nominal composition Ti-25at.%Al-10at.%Nb-3at.%V-1at.%Mo (Super α2) was evaluated following a high strain-rate forging to refine β grains (about 20 μm) and a heat treatment to partially transform β to an orthorhombic (O) phase with a fine dispersion of α2. Significant improvements in strength (0.2% yield strength about 900 MPa at room temperature and about 650 MPa at 650 °C) and room-temperature ductility were achieved from the fine-grained and O-transformed microstructure. In comparison with conventionally processed Super α2, the fatigue life was greatly superior (by more than two times). These improvements were achieved without compromise in creep-rupture and fracture toughness properties.