FATIGUE-CRACK PROPAGATION RESISTANCE OF A TI-48AL-2MN-2NB ALLOY IN THE AS-CAST CONDITION

In the present study the fatigue crack growth behaviour of a quaternar y Ti-48Al-2Mn-2Nb based alloy in the as-received condition was investi gated in air and vacuum at room temperature. The respective influence of crack closure and environment was more specifically examined. It wa s shown that closure induces a significant shielding resulting in a de crease in crack growth rates. The interactions of closure behaviour wi th test procedure is also discussed. Besides, ambient air was shown to severely enhance the crack growth. The role of moisture present in th e test environment is examined. Finally a detailed examination of the crack path and the rupture surface morphology has established features of the damage process.