Molecular dynamics simulations of the tensile mechanical responses of selective laser-melted aluminum with different crystalline forms

Abstract

The mechanical deformation of cellular structures in the selective laser melting (SLM) of aluminum was investigated by performing a series of molecular dynamics (MD) simulations of uniaxial tension tests. The effects of crystalline form, temperature, and grain orientation of columnar grains on the mechanical properties of SLM aluminum were examined. The MD results showed that the tensile strength of SLM aluminum with columnar grains at different temperatures was lower than that of single-crystal aluminum, but greater than that of aluminum with equiaxed grains. The tensile strength and Young’s modulus both decreased approximately linearly upon increasing the temperature. The deformation mechanisms of equiaxed and columnar grains included dislocation slip, grain boundary migration, and torsion, while the deformation mechanisms of single crystals included stacking fault formation and amorphization. Finally, the influence of the columnar grain orientation on the mechanical properties was studied, and it was found that the Young’s modulus was almost independent of the grain orientation. The tensile strength was greatly affected by the columnar grain orientation. Reasonable control of the grain orientation can improve the tensile strength of SLM aluminum.