## 1 Introduction
[20] investigated the effect of the scanning strategy on the residual stresses by resolving the laser beam in a single layer with an exposed area of 4 mm\({}^{2}\). The number of elements required for this study was high, due to the large expected cooling rate and laser spot size. [PERSON] [21] used a dynamic mesh coarsening algorithm. The mesh is fine where the laser surface heat flux interacts with the part and coarser in previously built layers, which effectively smears out the temperature and stress field in these layers. This strategy results in a high resolution simulation of a single cuboid, both thermally and mechanically. Similarly, [PERSON] et al. [22] investigated the effect of scanning strategy and geometry of the part on the final deformations. Since they need to investigate the effect of the scanning direction, the laser itself needs to be resolved. This necessitates the choice of a fine mesh and therefore a small computational domain. [PERSON] et al. [23] simplified the laser by bunching the real layers together in so-called meta-layers and applying flash heating--the top of the meta-layer was exposed to an aggregated heat flux. [PERSON] et al. [24] investigated the effect of the thermal expansion coefficient and the thermal diffusivity on the residual stress after the LPBF. To achieve this, they simulated different materials and validated the model for one of them. They show that a low thermal coefficient and high thermal diffusivity leads to a reduction of the residual stress. An experimental study by [PERSON] et al. [25] investigated the mechanisms behind the instability in single tracks analytically. [PERSON] et al. [4] developed a model which does not use the laser heat flux as such. They lump a number of tracks and layers together and deposit this block at the melting temperature. Since the goal of their model is to obtain an acceptable prediction for the stress field, the thermal calculation is coupled one-way with the stress calculation. Their high-speed simulation of the stress field shows good agreement with the more detailed investigation by [PERSON] [21]. [PERSON] et al. [26] show a good agreement between a finite-difference-based thermal model and the measured temperature in laser polishing. More recently, [PERSON] et al. [27] and [PERSON] et al. [28] performed similar calculations in a finite element framework, but their investigations included the stress build-up and fluid flow respectively. Experimentally, heat treatment of AM parts has been investigated extensively. Some examples include [PERSON] et al. [29], who investigated the effect of heat treatment on the residual stress for a part produced using LPBF. The alloy they investigate is an aluminium alloy, and by matching the measured deformation with a residual stress value, they find that the stress in the cantilever changes from 30% of the yield stress to around 5%. [PERSON] et al. [30] show a similar reduction of the residual stress due to a stress relaxation heat treatment. The alloy they investigated was a type of Cr-Mo steel. [PERSON] et al. [31] found that they could increase the hardness of a part produced in 300 grade maraging steel by aging at a lower temperature, around 460 \({}^{\circ}\)C.  
Studies focussing on modelling the heat treatment of AM parts are scarcer in the literature. An overview of modelling of heat treatment can be found in the review article by [PERSON] and [PERSON] [32]. The different possible parts in modelling of heat treatment are identified there as thermal calculation, phase transformation and deformation analysis. For AM specifically, the first two types of analyses are present in literature, either for similar processes such as post-casting [33], post-welding [34; 35] and even post-AM heat treatments [36], but the deformation analysis during a stress relief heat treatment remains absent. For AM, this is particularly problematic, due to the unique initial stress field and the effect of the final heat treatment on the geometrical accuracy.