Molecular Dynamics Study of Melt Structure and Transport Properties of Mg‒Al Alloy

Abstract

The development of magnesium alloy gigacastings puts forward higher demand on alloy fluidity because of more complex structure and longer filling distance. The fluidity is closely connected with atomic diffusion and melt viscosity. This work investigates the melt structure, self-diffusion coefficient, and viscosity of the Mg‒6wt.%Al alloy at different temperatures through molecular dynamics simulations. The melt structure is characterized by pair distribution functions, coordination numbers, H‒A index, and Voronoi polyhedron analysis. The self-diffusion coefficient is determined by the mean squared displacement method, whereas the viscosity is evaluated through the Green–Kubo equation and the Muller-Plathe algorithm. By establishing relationships among structure, diffusion, and viscosity, the microscopic mechanisms behind the temperature-induced changes in transport properties are revealed, in which the change of the degree of order at different temperatures is highlighted. The findings provide an atomic-scale theoretical basis for understanding the rheological behavior of magnesium alloy melt.

Keywords

diffusion coefficient / magnesium alloy / melt structure / molecular dynamics / viscosity

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