The paper investigates the combined effects of microstructural anisotropy and surface integrity on the fatigue performance of Ti6Al4V in wrought-equiaxed (W-E), wrought-lamellar (W-L), and laser powder bed fusion lamellar (LPBF-L) conditions under flood and cryogenic machining. Although the W-E condition shows the highest fatigue limit, it lacks the crack-deflection capability typical of lamellar microstructures. Among the lamellar states, LPBF-L exhibits greater resistance to crack propagation due to its lower anisotropy compared with W-L. Cryogenic machining improves fatigue behavior in all conditions, with lamellar microstructures benefiting the most, as their anisotropy promotes the formation of a thicker plastically deformed layer (PDL).
Bertolini et al. (Wed,) studied this question.