Mechanistic understanding of creep in gamma-base titanium aluminide alloys

The paper describes an experimental study of creep processes in two-phase t itanium aluminide alloys. The investigations involve long-term creep test a t relatively low stresses and temperatures. These test conditions lead to v ery low strain rates, which are characteristic of the intended service cond itions. The creep tests were coupled with detailed electron microscope obse rvations involving high-resolution imaging techniques and in situ heating s tudies. Long-term creep leads to spheroidization and coarsening of the lame llar morphology, which involve phase transformations and recrystallization. Climb velocities were analyzed in terms of the critical vacancy supersatur ation necessary for the operation of diffusion assisted dislocation climb s ources. The mechanisms are closely related to the atomic structure of the i nterfaces and are probably driven by a non-equilibrium phase composition. ( C) 2001 Elsevier Science Ltd. All rights reserved.