Molecular dynamics analyses of high-strain rate responses in metals containing zinc

Abstract

Molecular dynamics simulations that apply high strain rate to alloys containing zinc are performed, and the effects of zinc and strain rate on the mechanical behaviors of alloys are investigated. Zinc is mainly used for plating and alloying, and is the fourth most used metal for human beings. However, the modified embedded atomic method (MEAM) potential parameters were not available because the axial ratio of zinc is larger than 1.633. The original MEAM potential model using several MEAM parameters developed through existing studies while converting and utilizing the verified embedded atom method (EAM) parameters into MEAM parameters and the 2NN MEAM potential model that considers the relationship of each atom to the second nearest atom are proposed. Using the proposed potential model, molecular dynamics models of aluminum 7075 alloys both with and without the consideration of zinc and copper-zinc alloys with different content of zinc are prepared respectively. The effects of the considering zinc on the alloy and the zinc contents are investigated in several strain rates. As a results of the aluminum alloys, it is observed that the model with the consideration of zinc shows higher ultimate tensile strength than the model without the consideration of zinc. Moreover, suppression of the partial dislocation is noticed when zinc is present. The inclusion of zinc enhances the strength by inhibiting partial dislocation. In addition, the 2NN MEAM potential model, considering the relationship with the second nearest atom in detail, shows more accurate prediction than the original MEAM potential model. As a results of the copper-zinc alloys, it is observed that the strengths of the alloy models decrease as the zinc content increase, and the gradient change of the stress-strain curve is closely related to the transformation of FCC lattice to HCP lattice. Although the MEAM potential and the 2NN MEAM potential show the same trend in the change of the mechanical behavior according to the strain rate of the alloy containing zinc, it is highly recommended to use the 2NN MEAM for accurate calculation of the mechanical behaviors of alloys with various elements. It is expected that MD analysis of various alloys with zinc will be possible by using the MEAM potential and modeling method used in this study.