Environment effect on low cycle fatigue properties of some titanium alloys

In this paper an attempt is made to investigate the effect of the environment on the low-cycle fatigue properties of four titanium alloys. The influence of an elevated temperature (200-650 degrees C) and increased amount of hydrogen (0.004-0.08 wt %) in the alloy on the cyclic strength at constant-stress and constant-strain loading is analysed. Round (d = 10 mm) and rectangular cross-section (4 mm x 25 mm) smooth and notched specimens were tested. Fatigue crack initiation (length a approximate to 0.5 mm) and growth were observed by optical microscopy. The numbers of cycles to crack initiation and to final fracture were fixed. Analysis of the test data enabled the effects of both the temperature and hydrogen on the specimen lifetime to be determined.