Effect of heat treatment temperature and turning residual stresses on the plain and notch fatigue strength of Ti-6Al-4V additively manufactured via laser powder bed fusion

This paper investigates the fatigue strength of plain and notched specimens produced via laser powder bed fusion and heat-treated at different temperatures ranging between 800 °C and 950 °C. The effects of internal defectiveness and turning residual stresses are explored through computed tomography and X-ray diffraction. Residual stresses are eliminated in part of the experimental batches through a stress relief. The surface compressive residual stresses push the fatigue crack initiation site below the outer surface and increase the fatigue strength of the notched specimens. The heat-treatment temperature affects mostly the total elongation and the energy consumption, whereas its influence on the fatigue strength is less evident.