On low- and high-cycle fatigue ruptures at the same load in Ti-6Al-4V

Abstract

A series of measurements was made to obtain bending fatigue strength curves of commercial Ti-6Al-4V alloy at different temperatures, using notched and unnotched specimens with random and sinusoidal excitation. The results of sinusoidal fatigue tests show a gap at about 10 6 cycles between short and long fatigue life, which is explained by brittle nucleation at low cycles originating at preexisting microcavities on the surface caused by removal of crystals; the results also show ductility at high cycles. The nucleation is always brittle with random excitation. In all cases crack propagation is intergranular and takes place to a different extent in both brittle and ductile zones of the specimens.