Abstract
Laser-based powder bed fusion, due to its layer-by-layer nature, results in a unique stress profile in a part after the primary production process. The residual stresses are typically tensile near the top, while they are compressive near the bottom of the part. When it is removed without proper precautions, the part will bend excessively. In order to alleviate this deformation, a stress relief heat treatment can be applied. In this paper, such a stress relaxation heat treatment is modelled to investigate the effect of the post-processing parameters. The model uses an Arrhenius-type creep equation to simulate the influence of the heat treatment temperature and dwell time on the stress field in a relatively simple cantilever beam produced in Ti-6Al-4V. Via validation of the simulations, the effect of the heat treatment is shown to be represented accurately. The validated model is used to predict the deformation that results from the residual stresses after heat treating the part under various conditions. The results from the simulations ultimately allow choosing the optimal heat treatment conditions to obtain a given reduction in the residual stress level, while reducing the need for extensive experimental investigations.
Highlights
Additive manufacturing of metals allows the production of parts with a high complexity or low production volume at a limited cost
In order to investigate the effect of the stress relaxation heat treat ment on the residual stresses, a realistic initial field is required
This stress field follows from the process simulation in Abaqus CAE for the laserbased powder bed fusion (LPBF) process itself
Summary
Additive manufacturing of metals allows the production of parts with a high complexity or low production volume at a limited cost. The build plate is lowered by one step, and a new layer of powder is distributed. This process repeats until the part is completed [1]. When cooling down, the new layer cools down and contracts more than earlier deposited layers, causing tensile residual stresses in this final layer, and compressive ones near the bottom of the part [2]. When cutting the part from the base plate, part of the residual stresses are released, which can lead to deformation [3,4,5]. Differential contraction in neighbouring scan tracks cause residual stresses, but these typically do not affect the deformation as much as the layer-based ones [6,7]
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