Fatigue crack propagation rates have been measured for Ti-6A1-4V and T
i-5331S aeroengine disc materials using compact tension and corner-not
ched tensile testpieces. The loadings used simulate both the start-sto
p operations of aeroengines that lead to low-cycle fatigue and the in-
flight vibrations that may cause high-cycle fatigue. It is suggested t
hat the different fatigue crack growth behaviour of Ti-5331S, relative
to that of Ti-6A1-4V, arises largely from the greater proportion of c
rack closure and short crack growth occurring in this alloy. Ti-5331S
also exhibits a crack retardation effect due to the interaction betwee
n the processes of cyclic cleavage and striated crack growth which are
associated with the high- and low-cycle fatigue components of the loa
ding, whilst Ti-6A1-4V does not.