Thermomechanical fatigue behaviour of a γ-tial sheet material

The monotonic stress-strain behaviour, LCF and TMF behaviour of a Ti-46.5at.%-4at.%(Cr,Nb,Ta,B) alloy ingot metallurgically processed was investigated in the temperature range between 773 K and 1023 K. The ductile-to-brittle transition temperature (DBTT) was found to be 923 K. The cyclic stress-strain (CSS) response of LCF-tested specimens is characterized by an immediate state of cyclic saturation which continued up to failure. An increased fatigue life which is observed at elevated temperature is associated with a change of the fracture morphology from a transgranular cleavage type of fracture to a more dimple intergranular type. IP loaded specimens show the onset of dynamic recrystallisation which leads to an increased fatigue life as compared to LCF tests carried out at maximum temperature. OP loading is most detrimental with a well-reduced fatigue life, when compared to LCF tests carried out at the minimum temperature.