Computational study on the mechanical properties of lotus-type nanoporous magnesium under uniaxial tension and compression

Abstract

In this work, molecular dynamics (MD) simulation was performed to study the mechanical property of lotus-type nanoporous magnesium (Mg) under uniaxial tension and compression. Initial structure was treated by simulated annealing to obtain the stable state of surface atoms around the pore. After annealing, the porosity decreases and the atoms on the surface are in a disordered state due to rearrangement. Using the Voigt-Reuss-Hill (VRH) formula, we have deduced the elastic moduli based on calculated elastic constants for the annealed structure. The structure was declared as ductile according to Pugh criterion. Uniaxial tension and compression simulations were used to study the relationship among the stress–strain curves, the atomic crystalline phases and the vacancies-strain curves. For lotus-type nanoporous Mg, the main crystalline phases were also studied, combined with disordered atoms. The evolution of pore morphology is also different in the three directions. The shapes of pores after tension or compression are mainly cylindrical, elliptical and rhombic. The results of uniaxial tension and compression show that the faster the vacancy increases, the faster the stress decreases, and the number of vacancies is closely related to the change of atomic crystalline phases.