Abstract
The effects of microstructure morphorgy and the rolls of α2(Ti3Al) secondary phase on high temperature tensile property and creep rupture strength was investigated in structure controlled titanium aluminides. Three types of microstructure such as equi-axed, duplex and nearly lamellar were obtained by thermo-mechanical treatments performed in the α +γ phase field. As the volume fraction of α2 phase increased from Ti-50.8at%Al to Ti-48.5at%Al, with decreasing Al content tensile strength at high temperature was improved by the strength of theα2 phase itself and the stabilized lamellar structure which severely obstructed deformation. On the other hand, specimens with the stabilized lamellar structure in Ti-48.5at%Al showed little tensile elongation as little as 5% even at 1173K. The stabilized lamellar structure by α2 phase also interferes with recrystalization during deformation, leading to a significant increase in creep rupture strength.
