Modified embedded atom method potential for Al, Si, Mg, Cu, and Fe alloys

A set of modified embedded-atom method (MEAM) potentials for the interactions between Al, Si, Mg, Cu, and Fe was developed from a combination of each element's MEAM potential in order to study metal alloying. Previously published MEAM parameters of single elements have been improved for better agreement to the generalized stacking fault energy (GSFE) curves when compared with ab initio generated GSFE curves. The MEAM parameters for element pairs were constructed based on the structural and elastic properties of element pairs in the NaCl reference structure garnered from ab initio calculations, with adjustment to reproduce the ab initio heat of formation of the most stable binary compounds. The new MEAM potentials were validated by comparing the formation energies of defects, equilibrium volumes, elastic moduli, and heat of formation for several binary compounds with ab initio simulations and experiments. Single elements in their ground-state crystal structure were subjected to heating to test the potentials at elevated temperatures. An Al potential was modified to avoid formation of an unphysical solid structure at high temperatures. The thermal expansion coefficient of a compound with the composition of AA 6061 alloy was evaluated and compared with experimental values. MEAM potential tests performed in this work, utilizing the universal atomistic simulation environment (ASE), are distributed to facilitate reproducibility of the results.

Figure 1

Energy-volume dependence of Al, Si, Mg, Cu, and Fe in fcc, hcp, bcc, diamond, and simple cubic crystal structures relative to the ground state.

Figure 2

GSFE curves for Al, Mg, Cu, and Fe obtained with the MEAM potential and compared with the DFT data.

Figure 3

Heat of formation of AlSi, AlMg, AlCu, AlFe binary compounds from MEAM, DFT, and experiments. References: AlSi,[9] AlMg,[100] AlCu,[101, 102, 103, 104] and AlFe.[105, 106, 107] DFT points are labeled on the left, MEAM and experimental on the right. Values for the most stable compounds are also shown in Table . The inside plot is a magnified portion of a larger plot.

Figure 4

Heat of formation of SiMg, SiCu, SiFe, and MgCu binary compounds from MEAM, DFT, and experiments. References: SiMg,[104] SiCu,[108, 109] SiFe,[100, 110] and MgCu.[100, 111] DFT points are labeled on the left, MEAM and experimental on the right. Values for the most stable compounds are also shown in Table . The inside plot is a magnified portion of a larger plot.

Figure 5

Heat of formation of MgFe and CuFe binary compounds from MEAM and DFT. References: MgFe,[100] CuFe.[100] DFT points are labeled on the left, MEAM on the right. Values for the most stable compounds are also shown in Table .