Residual stress of as-deposited and rolled wire+arc additive manufacturing Ti–6Al–4V components

Abstract

Wire + arc additive manufacturing components contain significant residual stresses, which manifest in distortion. High-pressure rolling was applied to each layer of a linear Ti-6Al-4V wire + arc additive manufacturing component in between deposition passes. In rolled specimens, out-of-plane distortion was more than halved; a change in the deposits' geometry due to plastic deformation was observed and process repeatability was increased. The Contour method of residual stresses measurements showed that although the specimens still exhibited tensile stresses (up to 500 MPa), their magnitude was reduced by 60%, particularly at the interface between deposit and substrate. The results were validated with neutron diffraction measurements, which were in good agreement away from the baseplate.

Residual Stress Characterization and Control in the Additive Manufacture of Large Scale Metal Structures

“…The Out-of-Plane distortion of the control sample is 6.8 mm, which is comparable to what has been found before [4]. Fig.…”

“…4 shows the distortion of the eight rolled samples vs. the rolling load. Post-weld side rolling shows a greater reduction in distortion with increasing rolling loads and decreasing roller diameter as known from previous work [4], [6]. Comparing the roller diameters, the smaller roller always showed a greater reduction in distortion for the same load by approximately 1 mm.…”

“…After unclamping, the profile shows a constant drop of residual stress with increasing distance to the substrate, with being compressive in the top layers. This trend is also supported by this model and also reported elsewhere [3], [4], [8]. Side Rolling took place from 3 mm above the substrate to the top of the wall.…”

“…2 e). Hence vertical rolling can only reduce residual stress and distortion in Ti-6Al-4V WAAM, but not eliminate them entirely [4]. In Colegrove et al [3] this lateral deformation was successfully attempted to restrain for the first time by using "slotted roller".…”

“…2 a) to c). [4]. A promising mechanical technique to manipulate the residual stresses and distortion is cold rolling, which initially has been used on butt welds (Fig.…”