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

• As-built samples have shown increased α-lath width along the build direction. • HIPing helped to remove the graded microstructure and increased α-lath width by 50%. • Graded microstructure in as-built samples led to graded cyclic softening behaviour. • As built samples from the bottom showed 38% lower plastic strain range than the top. • Application of HIPing reduced the graded cyclic deformation behaviour. 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. [ABSTRACT FROM AUTHOR]