Numerical Modeling of the Phase Transformation and Morphology Evolution of Polyamide 12 in Laser Powder Bed Fusion Process at Particle Scale
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Phase transformation and morphology evolution are two critical topics in studying the semi-crystalline polymer laser powder bed fusion (L-PBF) process. In this work, a particle scale numerical model of LPBF for polyamide-12 (PA12) is presented. The model is developed by the finite element method under the framework of the level-set method. The asymmetrical and kinetical phase transformation behavior of semi-crystalline polymer is implemented in the thermal model. Based on this, the particle consolidation phenomenon under laser irradiation is simulated by hydrodynamics. The physical properties of PA12 powder are identified by experiments regarding the inputs of the numerical model. Before performing L-PBF processing simulations, the numerical powder bed model, the implementation of crystallization kinetics, and the related hydrodynamic parameters are verified by performing the comparison of simple simulation with the experiments. For single-track simulation, the influence of phase transformation latent heat on the melting pool profile is discussed, and thus the modified crystallization kinetics is highlighted. The effect of processing parameters on the temperature field and shape of the melting pool are also modeled. Finally, optical observations are conducted to validate the simulated morphology of the melting pool, and a good agreement between numerical results and experimental observations is obtained, indicating the ability of the numerical model to simulate the PA12 L-PBF process.