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Axial-torsional thermo-mechanical fatigue of Ti-45Al-5Nb-0.2B-0.2C
Structural components in aeronautical gas turbine engines typically experience large variations in temperatures and multiaxial states of stress under non-isothermal conditions. The behavior of a gamma titanium aluminide (TiAl) intermetallic under uniaxial, torsional and axial-torsional thermo-mechanical fatigue (TMF) was studied. TMF tests were performed at 400-800 degrees C with mechanical strain amplitudes ranging from +/- 0.15% to +/- 0.3%. The tests were conducted thermo-mechanically in-phase (IP) and out-of-phase (OP). Stress-strain hysteresis loops, cyclic deformation curves, fatigue lives and microstructures were evaluated. Investigations have shown that small variations in strain amplitude considerably affect lifetimes. The uniaxial IP tests require higher strain amplitudes than the uniaxial OP tests with similar lifetimes. For the same equivalent mechanical strain amplitude uniaxial IP tests have significantly longer lifetimes than all other performed tests.