SUPERPLASTIC BEHAVIOR OF NANOSTRUCTURED INTERMETALLIC Ti_2AlNb-BASED ALLOY

摘要

Homogeneous microstructure with the average grain size of 300 nm was produced in Ti_2AlNb-based intermetallic alloy by a thermomechanical processing which included multistep isothermal forging at temperatures below the β-transus and intermediate annealings. Nanostructured material possessed excellent mechanical properties. At room temperature, elongations up to 25% were obtained and the ultimate strength reached 1400 MPa. The alloy exhibited superplastic behavior in the temperature range of 850-1000°C. The maximum elongation of 930% and steady state flow stress σ_(50) of about 125 MPa were obtained at 900°C and strain rate of 4.2×10~(-3) s~(-1). The rolling temperatures of nanostructured alloy were defined from analysis of its mechanical behavior at a typical rolling strain rate of about 10~(-1) s~(-1) and intermetallic sheets with improved mechanical properties were produced.