Effect of Microstructure Control on the Mechanical Properties of Hot Worked TiAl Alloy

Abstract

The microstructure and mechanical properties of a newly developed, β-phase containing TiAl alloy have been studied through hot working and post heat treatment to enhance room temperature ductility and strength. The controlled microstructures hadthree types of structure, fully lamellar, nearly lamellar and duplex, and were produced by cyclic heat-treatment in a single α region and (α+γ) region after a hot-forging process in high temperature (α+β) region. As a result of the room temperature tensile test, the fully lamellar structure exhibited a tensile strength of 622 MPa and ductility of 0.62%. The duplex structure had a tensile strength of 787 MPa and ductility of 1.22%, while the nearly lamellar structure showed a tensile strength of 880 MPa and ductility of 1.76%. In the room temperature tensile test, the nearly lamellar structure exhibited excellent tensile strength and ductility. The strength and ductility were increased by decreasing grain size and β / B2 phase fraction. The newly developed TiAl alloy showed higher tensile values compared with the previous TiAl alloys. The relationship between microstructure and room temperature tensile properties of the newly developed β-phase containing TiAl alloy was examined, and the best approach for hot working and post heat-treatment to obtain the most balanced mechanical properties was proposed.