Creep deformation of α2 Ti3Al intermetallics in the low stress region

Microstructure has been studied to understand creep behavior under low stresses in α2 Ti3Al-base single-phase polycrystalline alloys containing 27.5 and 34.0 mol% Al. TEM observations were done on specimens crept up to the stage of the minimum creep-rate (εm≈0.1). Well-developed sub-boundaries are formed. Many dislocations are distributed homogeneously within subgrains. The dislocation density is almost independent of temperature and Al concentration, but increases with increasing stress. The stress exponent for the dislocation density is about 1.7. Dislocations with the (a+c)-component are observed, as well as those with the a-component. The former is only about 1/4 of total dislocations and this ratio is almost unchanged with stress, temperature, and Al concentration. It is suggested that the activity of dislocations with the a-component controls the creep behavior of these materials under low stresses.