Influence of yttrium on the high temperature deformability of TiAl alloys

The effects of yttrium additions on plastic deformability and the change of microstructures after deformation of TiAl alloys were investigated by isothermal hot-compression pressing. The experiments were conducted with the Gleeble-1500D style of thermo-force analogue machine. The results indicated that the higher the deformation temperature and the lower the strain rate, the smaller the deformation resistance, and adding 0.3 at.%Y can improve remarkably hot deformability of Ti–43Al–9V and Ti–45Al–5Nb alloys at the same processing parameters. Comparing with the microstructures of Y-free TiAl alloys after deformation, the grain sizes of Y-containing TiAl alloys were much finer and the fraction of the fine equiaxed γ grains formed by dynamic recrystallization increased, and the addition of 0.3 at.%Y decreased the flow stress, the deformation activation energy of Ti–43Al–9V and Ti–45Al–5Nb (numbers indicate at.%) alloys. According to the isothermal hot-compression pressing results, appropriate sets of deformation processing parameters are recommended for the present Y-containing TiAl alloys. These recommended hot deformation processing parameters have been successfully used for the quasi-isothermal canned forging of (0.3%)Y-containing TiAl alloy billets.