CREEP-BEHAVIOR OF TI-25AL-10NB-3V-1MO

A study has been made of the role of microstracture in room-temperature tensile properties as well as elevated-temperature creep behavior of an advanced Ti3Al-base alloy, Ti-25Al-10Nb-3V-lMo (atomic percent). Creep studies have been performed on this alloy as a function of stress and temperature between 650 °C and 870 °C, since the use of conventional titanium alloys has generally been restricted to temperatures below 600 °C. A pronounced influence of microstructure on creep resistance was found. Generally, the β solution-treated colony-type (slow-cooled or SC) microstructure showed superior creep resistance. This improved creep resistance in β/SC is accompanied by lower room-temperature tensile strength and ductility. Study of the stress dependence of steady-state creep rate indicates that increasing temperature caused a gradual decrease in the stress exponent n and a transition in creep mechanism at 870 °C, depending on applied stress level. Transmission electron microscopy observations of deformed dislocation structures developed during steady-state creep and room-temperature tensile tests, as well as the corresponding fracture modes, were used to interpret properties as a function of temperature. Finally, creep behavior of the present Ti3Al alloy was found to be superior to that of conventional near-α titanium alloys. © 1990 The Metallurgical of Society of AIME.