Correlation between local structure and glass forming ability enhanced by similar element substitution in (La-Ce)-Co-Al bulk metallic glasses

摘要

Similar element substitution is an effective strategy to develop bulk metallic glasses (BMGs) with high glass forming ability (GFA). However, the relationship between the local structure and the GFA enhancement has not been clarified when similar element is introduced. In this paper, the local structures of the ternary La_(65)Co_(25)Al_(10) and pseudo-ternary (La_(0.7)Ce_(0.3))_(65)Co_(25)Al_(10) BMGs were studied by ab-initio molecular dynamics. Partial pair correlation function, bond angle distribution, coordination number, solute-solute avoidance, Voronoi polyhedron, and free volume were used to characterize the local structure. After partial substitution of Ce for La, the (La_(0.7)Ce_(0.3))_(65)Co_(25)Al_(10) BMG exhibited higher degree of solute-solute avoidance, more icosahedral-like Voronoi polyhedrons, and less free volume, which may be the structural origin of the higher GFA induced by similar element substitution.