Creep properties of Ti-48Al-2Cr-2Nb alloy having similarly oriented lamellae with fine lamellar spacing

The tensile creep behavior of suction-cast and heat-treated Ti-48Al-2Cr-2Nb (at. pct., SC4822) alloy featuring aligned lamellar microstructure with fine lamellae was investigated. The alloy showed excellent creep performance in the temperature range of 775-825 degrees C under applied stresses varying from 200 to 350 MPa. The creep properties of SC4822 alloy greatly outperformed that of several other typical TiAl alloys with randomly oriented lamellae. The stress exponent (n) for SC4822 alloy was calculated to be 5.1 at 800 degrees C under different stresses, whereas the apparent activation energy (QC) was found to be 397.18 kJ/mol under 300 MPa at different temperatures. This suggested that creep deformation was dominantly controlled by dislocation climb, as confirmed by subsequent microstructure observation. Besides, dynamic recrystallization, twinning and slipping were also found to contribute to the deformation of creep.