Elastic and structural properties of Mg25Al75 binary metallic glass under different cooling conditions

Abstract

Molecular dynamics (MD) simulations based on the embedded atomic method (EAM) are used to study the annealing effect on elastic and structural behavior for different cooling rates of binary Mg25Al75metallic glasses (MGs). Firstly, we examine the cooling rates effect (5×1011K/s, 1012K/s,5×1012K/s and 1013K/s) on the atomic locale structure of Mg25Al75MG through a variety of local structure analysis methods such as bond angle distribution (BAD), total and partial radial distribution function (RDF), Voronoi tessellation analyses (VTA) and coordination numbers (CNs). Our results confirm that the Mg25Al75 glass formation is proved by a splitting of the second peak in the RDF upon quenching process. The<0,0,12,0>,<0,1,10,2> and<0,2,8,4> Voronoi polyhedrons (VPs) have been depicted as the most dominant polyhedrons in the system, and we have found that the <0,0,12,0>,<0,1,10,2> clusters increase while the <0,2,8,4> cluster decreases as a function of the decrease of the cooling rate. Via the Went-Abraham parameter, our numerical results show an increase of the glass transition temperature (Tg) with increasing of cooling rate. Finally, we heat-treated the binary Mg25Al75MG samples at the aging temperature 450 K during period varying from 0 to 5 ns for four different quenching rates. We observed that the elastic constants C11and C44 increase while C12decreases as the annealing time increases and the quenching rate decreases. This has been correlated with the elastic moduli, where Young’s modulus (E), bulk modulus (B) and shear modulus (G) increase, which suggests the improvement of the elastic behavior, the resistance to compression and the resistance to the shear bands (SBs), respectively. We also found that at the atomic level in the short-range order (SRO), the <0,0,12,0>and<0,1,10,2> clusters and the degree of the five-fold symmetry increase as a function of the increase of annealing time.