## 1 Introduction
[11] developed a hierarchical computational model for moving thermal loads and phase changes. The model was based on hp-finite elements, which varied the size of the element and the high polynomial degree because of strong gradients. The mesh was refined towards the entire laser path and kept fixed at all time steps. [PERSON] and [PERSON] [12] surveyed the temperature and thermal stress fields of SLM/SLS and electron beam melting (EBM). [PERSON] and [PERSON] [13] developed a 3D mesoscopic model to simulate selective laser melting processes using the ALE3D multiphysics code. They studied the laser-induced melting of a random bed of 316 atomized stainless steel particles on a solid substrate and its solidification. The simulations were used for further powder homogenization. [PERSON] et al. [14] developed a transient three-dimensional (3D) beam-matter-interaction model to simulate the process dynamics of laser beam melting of metals in the powder bed. The simulations were realized by the software OpenFOAM (Open Field Operation and Manipulation), and studies were performed on the regularly deposited powder with atomized (spherical) particles of the same sizes. The effects of powder layer thickness, heat source intensity, scan spacing, and scanning velocity on the process dynamics were simulated. [PERSON] et al. [15] investigated the melting and resolidification of a randomly packed powder bed with round particles using a 2D model based on the lattice Boltzmann method (LBM). Numerical simulation considered individual powder particles and took into account any physical phenomena, e.g., the influence of the relative powder density, the stochastic effect of a randomly packed powder bed, and capillary and wetting phenomena. Similar principles are applied in the project presented in this paper. [PERSON] et al. [16] simulated the size of a single-layered 316L stainless steel melt pool during the SLM process using a 3D FEM model. They modeled the optical penetration depth of the laser beam into the powder bed and its dependence on the powder size and the heat source. The results were validated with the experimental results. The model was used to predict the effect of different scanning speeds on melt pool depth, width, and length. [PERSON] et al. [17] simulated laser fusion additive manufacturing processes using the smooth particle hydrodynamics (SPH) method. It is a Lagrangian mesh-free numerical scheme adapted to resolve thermal-mechanical-material fields. They noted that the SPH method is a viable and promising numerical tool for simulating laser fusion-driven additive manufacturing processes. They applied the model to powders with regularly deposited spherical particles of the same sizes. Many publications are devoted to microstructure evolution during the SLM process, e.g., [18; 19; 20; 21; 22; 23; 24]. [PERSON] et al. [18] studied local solidification conditions to develop a scanning strategy to achieve grain orientation by changing the thermal gradient during solidification. They used a model based on a 2D LBM. An interesting complex approach is presented by [PERSON] et al. [19]. They studied the thermal fluid flow and microstructural evolution of a set of single tracks scanned with a laser with different thicknesses of the powder layer and scanning speeds during SLM and analyzed single-track morphology, porosity formation, and melt flow behavior. They used both computational and experimental approaches. A computational fluid dynamics (CFD) calculation was developed using the C++ open-source CFD toolbox (OpenFOAM) to model the interaction between the laser heat source and the randomly distributed Ti-6 Al-4V powder materials. [PERSON] et al. [20] used Layerwise Additive Manufacturing Predictions and Simulations (LAMPS) software to analyze the full-scale temperature field response and quantitatively explain the experimental results of the 6061 Al alloy and the TiC-reinforced 316L stainless steel SLM process. [PERSON] et al. [21] also analyzed the microstructure evolution of AlSi10 Mg on a single track using FEM.