Finite Element Analyses of Macroscopic Stress-Strain Relations and Failure Modes for Tensile Tests of Additively Manufactured AlSi10Mg with Consideration of Melt Pool Microstructures and Pores

Finite element (FE) analyses of macroscopic stress-strain relations and failure modes for tensile tests of additively manufactured (AM) AlSi10Mg in different loading directions with respect to the building direction are conducted with consideration of melt pool (MP) microstructures and pores. The material constitutive relations in different orientations of AM AlSi10Mg are first obtained from fitting the experimental tensile engineering stress-strain curves by conducting axisymmetric FE analyses of round bar tensile specimens. Four representative volume elements (RVEs) with MP microstructures with and without pores are identified and selected based on the micrographs of the longitudinal cross-sections of the vertical and horizontal tensile specimens. Two-dimensional plane stress elastic-plastic FE analyses of the RVEs subjected to uniaxial tension are then conducted. The true stress-plastic strain curves for MPs and melt pool boundaries (MPBs) are obtained in scale with those of the tensile tests based on the microhardness values. The simulation engineering stress-strain curves of the RVEs are in good agreement with the experimental data. The simulation results indicate that the plastic deformation is initiated at the soft MPBs and near the material defects of pores, grows along MPBs in the vertical specimens or across MPs in the horizontal specimens as the macroscopic strain increases, and finally possible fracture paths connecting the regions with large plastic strains are identified. The identified failure modes are in good agreement with those from experiments. The simulation results also indicate that the MP microstructures and pores play important roles in the failure modes and anisotropy of ductility of AM AlSi10Mg.