Structural and mechanical behaviors of Mg-Al metallic glasses investigated by molecular dynamics simulations

Abstract

Using molecular dynamics simulations with the embedded atomic method (EAM) to describe interatomic interactions, structural and mechanical properties of Mg-Al metallic glasses (MG) have been investigated for different compositions. The atomic structure is characterized using various techniques such as the Radial Distribution Function (RDF), the Voronoi Tessellation Analysis (VTA) and coordination number (CN) distribution. The results confirmed that the Mg-Al glass formation is accompanied by a splitting of the RDF second peak upon cooling process. The glass transition temperature is determined using different method involving a new suggested way consisting of the cross-over between low and high coordination numbers curves during cooling process. This last technique gives approximate results that converge to those given by classical methods. On the other hand, we applied a strain-rate of 1010 s−1 at 300 K and showed that with the increase of Al composition, the maximal stress increases as a function of strain. For a fixed composition of Mg-Al MG, the yield strength increases with the increase of strain-rate between 109 s−1 and 1010 s−1. The impact of temperature on the mechanical behaviour of Mg-Al under various strain-rates has been investigated and the result suggests that for the same applied strain-rate, the ultimate tensile strength decreases as a function of temperature. Finally, the annealing effect has led to a softening of elastic moduli especially the Young modulus (E) which has been determined through both elastic constants Cij and from the stress–strain curve.