The structural evolution and abnormal bonding ways of the Zr80Pt20 metallic liquid during rapid solidification under high pressure

Abstract

The structural evolutions and abnormal bonding ways of the Zr80Pt20 binary alloy during rapid solidification under different pressures from 0 to 120 GPa have been investigated by classical molecular dynamics simulations in conjunction with the embedding atom method. The pair distribution function, the coordination number, the Warren-Cowley parameter, the bond length and the pair analysis technique are used to reveal the structural evolution of the Zr80Pt20 solidified under normal and high pressures. Persuasive evidence indicates that the applied pressure strongly affects the vitrification (for 0 ≤ P ≤ 20 and 90 ≤ P ≤ 120 GPa) and crystallization (for 30 ≤ P ≤ 80 GPa) processes of the metallic liquid and causes significant changes in the microstructure of the system. Interestingly, we have observed that the crystallization for the Zr80Pt20 system is associated with volume expansion between 50 and 80 GPa, in contrast to the volume contraction observed under 30 and 40 GPa. The results of the atomic structure analysis show that there is an unexpected shortening of Zr-Zr bonds under high pressures, which is related to the change of the atomic packing in the Zr80Pt20 alloy from loose to dense with increasing pressure. The results of the analysis show that the bonds between Zr-Zr and Pt-Pt pairs can be shortened more easily than the bonds between Zr-Pt pairs at high pressures and also the clustering behaviors of Zr-Zr or Pt-Pt bonds reveals the presence of composition segregation. This study presents encouraging findings for the experimental investigation of glass transition and crystallization processes in Zr-Pt metallic liquids during rapid cooling and under high pressure.