Finite-element analysis and experimental validation of thermal residual stress and distortion in electron beam additive manufactured Ti-6Al-4V build plates

A 3D transient fully coupled thermomechanical model was built to study the distortion and residual stress in electron beam additive manufactured Ti-6Al-4V build plates. Single layer, 6-layer and 11-layer build plates were investigated using both simulation and experiments to ensure the accuracy of the model and provide confidence in using simulations for process optimization. The model was validated by comparing the predicted residual elastic strains against measured values obtained by neutron diffraction for the 11-layer build plate. The longitudinal component of strain, parallel to the beam trace, is the most significant component. A double-peak tensile strain distribution was found in the cross-section of the substrate. The plate distortion was also measured for comparison with the model simulations. The simulated distortion and residual strains are in good agreement with the experimental results. The effect of preheat on the distortion and the residual stress distribution was then studied using the validated model. The modeling results show that preheating at least twice is an effective way to reduce both distortion and residual stresses.