THE MICROSTRUCTURE AND CREEP-BEHAVIOR OF TI-25AL-10NB-3V-1MO (SUPER A(2))

Low-oxygen plasma-melted Ti-25Al-10Nb-3V-1Mo (super alpha(2)) has been isothermally upset forged at 1050 degrees C(alpha(2) + beta phase fie ld) and then heat-treated to produce different microstructures. The cr eep behaviour has been examined as a function of microstructure, stres s and temperature. Test temperature ranged from 650 degrees C to 750 d egrees C, test stress ranged from about 50 MPa to about 200 MPa and th e tests were conducted in air. The microstructures of specimens were e xamined by optical and transmission electron microscopy. The steady st ate creep rate, apparent stress exponent and apparent creep activation energy of the various samples have been determined and compared with those in the literature. The results show, as expected, that the creep properties are strongly influenced by microstructure. The significanc e of these observations is discussed in terms of the parameters that c ontrol secondary creep in super alpha(2).