Cyclic plasticity and damage mechanisms of Ti-6Al-4V processed by electron beam melting

Cyclic deformation and damage mechanisms in electron-beam-melted Ti-6Al-4V are investigated. As-built samples exhibit a graded microstructure over the height of 120 mm, with samples from the top having larger α-laths and higher plastic strain. After HIPing, the α-lath width is greater, with reduced grain misorientation, and lower microstructural and property gradients. In both conditions, the observed cyclic softening is dominated by a monotonic reduction in the friction stress and an increase in grain misorientation, suggesting the lath structure progressively fragments into smaller grains. As-built samples show typically lower fatigue life due to crack initiation from gas pores and lack-of-fusion defects.