FATIGUE-CRACK INITIATION IN HIGH-PURITY TITANIUM CRYSTALS

Fatigue crack initiation has been studied in high-purity titanium mono crystals, bicrystals and polycrystals. Concerning persistent slip band s (PSBs), two fatigue damage modes were identified: holes and cavities along the bands, and microcracks perpendicular to the bands. The inte ractions of grain boundaries with slip bands or cyclic twins were obse rved to induce fatigue cracks. In addition to the twin-matrix interfac es, impinging between twins and extrusion ribbons within twins were al so found to be preferential sites for crack nucleation. The mechanisms of fatigue crack initiation are discussed. Copyright (C) 1996 Elsevie r Science Limited