ROOM-TEMPERATURE LOW-CYCLE FATIGUE BEHAVIOR OF TI-27AL-15NB ALLOY

Low-cycle fatigue (LCF) behaviour of the alloy Ti-27Al-15Nb, in (alpha (2) + B2) heattreated condition was studied in total axial strain cont rol mode at different total strain amplitudes (Delta epsilon(t)/2) fro m +/- 0.65 to +/- 1.0% and room temperature. While there was little ha rdening of the material at the lowest strain amplitude (Delta epsilon( t)/2:+/- 0.65%), pronounced hardening was observed at the higher strai n amplitudes (Delta epsilon t/2 greater than or equal to 0.83%). The c yclic stress, at high strain amplitudes, continuously increased from t he beginning till fracture of the specimens. The LCF resistance of the material was found to be low and this was due to its poor ductility a t room temperature. Dual slope was observed in the Coffin-Manson plot, with less slope of the upper segment than that of the lower one, as o bserved in several alloys. The fracture behaviour pointed to brittlene ss and faceted features were observed.