Production and characterization of TiAl ribbons with Y additions

Abstract

Rapid solidification method was employed to produce TiAl based alloy ribbons and finally to produce TiAl based alloys with novel microstructure and properties. TiAl based alloys with nominal compositions of Ti-46Al-2Cr-2Nb (atomic ratio) and various yttrium additions (0, 0.5%, 1.0%, 1.5%, 2.0%, atom fraction) were produced using the melt spinning method. For comparison, cast alloys with the same compositions were prepared by argon arc melting as well. It is shown that the as cast microstructure of Y free alloy is lamellar. With addition of Y up to 1.5%, the microstructure of the alloy changes from lamellae to dendrites, while more addition of Y leads to a finer dendrite structure. For the rapidly solidified TiAl based alloy ribbon, refined microstructure is produced. The increase of Y addition modifies the phase constituents from pure γ-TiAl phase of Y free alloy gradually to γ-TiAl+α 2-Ti 3Al and γ-TiAl+α 2-Ti 3Al+small amount of Al 2Y phase. Though the phase constituents on the two sides of ribbons, surface contacting roll and free surface, are essentially the same, the microstructure of the former one is much finer than that of the latter one.