A three-dimensional geometrical model for the microstructure of additively manufactured metals

Abstract

In the last few decades, selective laser melting has been adopted in a broad range of applications, including automobile, aerospace, medical, and robotic industries, mainly because of the unique versatility of this method in fabricating complex parts. Despite all the advantages of the method, the quality and the mechanical properties of the manufactured parts are drastically affected by the microstructure and processing parameters. Since the fabrication and characterization of test samples are time-consuming and expensive, developing reliable and accurate models to investigate the correlation between the microstructure and the mechanical properties at the bulk scale is a necessity. In this paper, a three-dimensional geometrical model, which explicitly considers the grains, melt-pools, and melt-pool boundaries, is developed. In this model, first, the grain microstructure is constructed by random Voronoi tessellation of a cubic domain to coincide with reality. Then, considering the melt-pool boundaries’ position and orientation, the redundant portions of the grains are removed. Finally, the complete model is constructed by assembling all the remaining grains. In addition, a method for selecting the randomly distributed grain boundaries and melt-pool boundaries is introduced. The accuracy of the proposed model in considering the texture is validated by comparing the pole figures against those obtained from electron backscatter diffraction tests, and a good agreement is shown. The results show that the pole figures of the model converge to those of the experiment when the number of grains is increased. In addition, some geometrical models are generated by adjusting different process parameters, that is, hatch space, layer thickness, and scan strategy, to see how capable the model is in generating accurate misconstrues. The observations prove that the proposed geometrical model can resemble all the details with good accuracy and can be used for numerical simulation purposes.