Fatigue crack propagation resistance of a Ti48Al2Mn2Nb alloy in the as-cast condition

In the present study the fatigue crack growth behaviour of a quaternary Ti48Al2Mn2Nb based alloy in the as-received condition was investigated in air and vacuum at room temperature. The respective influence of crack closure and environment was more specifically examined. It was shown that closure induces a significant shielding resulting in a decrease in crack growth rates. The interactions of closure behaviour with test procedure is also discussed. Besides, ambient air was shown to severely enhance the crack growth. The role of moisture present in the test environment is examined. Finally a detailed examination of the crack path and the rupture surface morphology has established features of the damage process.