TENSILE DUCTILITY AT ROOM-TEMPERATURE IN THERMO-MECHANICALLY TREATED GAMMA+ALPHA-2 TYPE TITANIUM ALUMINIDES

The effects of thermo-mechanical treatment on the tensile ductility at room temperature were investigated in the three binary gamma-base titanium aluminides containing different volume fraction of alpha2 phase. The tensile ductility at room temperature was improved by the formation of fine and homogenious ''duplex'' microstructure, which was optimised by the high reduction of forging and the adequate heat treatment temperature. The effect was most remarkable on the stoichiometric composition containing less alpha2 content than Ti-rich composition. In the duplex microstructure, deformation was taken upon the equi-axed gamma grains rather than the lamellar region. However, the fracture mode was still brittle even in the specimen showing the high elongation of 7.8%.