Microstructure, texture and mechanical properties of Ti-43Al-9V-0.2Y alloy hot-rolled at various temperatures

Using the hot-pack rolling method, β-solidifying Ti-43Al-9V-0.2Y alloy sheets were rolled (thickness reduction: 85%) within the α(α₂) + β + γ ternary-phase region at temperatures ranging from 1100 °C to 1200 °C. The microstructure and texture evolution occurring during dynamic recrystallization of the γ phase and their effect on the mechanical properties were systematically investigated. After hot-rolling, residual lamellar structures of the as-forged TiAl alloy were completely broken down and the fraction of dynamically recrystallized grains increased significantly with increasing rolling temperature. Lower-temperature and higher-temperature rolling were conducive for dynamic-recrystallization nucleation and growth, respectively, of the γ grains. At 1100 °C, the precipitation of numerous fine (thickness: ∼200 nm) γ laths from the β-phase ribbon was accompanied by the emergence of γ twins in the new grains. The texture evolution was also strongly dependent on the hot-rolling temperature, as evidenced by the transformation of recrystallization textures into random deformation components when the temperature was increased to 1200 °C. Moreover, compared with those rolled at higher temperatures, the sheet hot-rolled at 1100 °C had a significantly higher tensile strength (ultimate tensile strength (UTS): 945 MPa, yield strength (YS): 840 MPa) at room temperature. A good combination of high strength (UTS: 550 MPa, YS: 480 MPa) and sufficient ductility (80%) of this alloy sheet was also achieved at 750 °C.