A new approach to obtaining fine-grained structure in intermetallic- compound alloys such as γ-TiAl + α2-Ti3Al has been suggested. This approach is based on the use of alloys that solidify as the β phase, which contain β-stabilizing additives such as Nb and Mo and are characterized by the small size of crystallites already in the cast state; in these alloys, a simple heat treatment makes it possible to substantially decrease the fraction of the lamellar component and to increase the content of the β(B2) phase. It is shown on the example of the Ti-43Al-7(Nb,Mo)-0.2B (at %) alloy that this heat treatment ensures superplastic properties in the material in the temperature range of T = 1050-1130°C at a deformation rate = 1.7 × 10-4 K-1. Under these temperature-strain-rate conditions, relative elongations such as δ = 160-230% and low flow stresses such as σ = 36-100 MPa characteristic of superplastic flow have been obtained. It has been shown for the first time for the intermetallic γ-TiAl + ga2-Ti3Al alloy that a sheet semifinished product cut out from an ingot subjected only to heat treatment can have plasticity acceptable for press forming.
- intermetallic-compound alloys
- heat treatment