ENVIRONMENTAL INFLUENCE ON FATIGUE-CRACK PROPAGATION IN TIAL ALLOYS

The fatigue crack growth behaviour of a quaternary Ti-48Al-2Mn-2Nb is investigated with a special emphasis on the role elf environment. The fatigue crack-growth resistance is shown to be significantly lessened in ambient air. This is due to a lack of complementary shielding from oxide-induced closure in conjunction with an environmental enhancement of fatigue damage at the crack tip. This enhancement is proved to be related to the moisture content of the test atmosphere regardless of t he oxygen content. Finally, the nature of this fatigue crack growth en hancement is discussed. (C) 1997 Published by Elsevier Science Limited .