Study on topologically close-packed and crystal clusters of Cu10Ag90 alloy at the critical crystalline cooling rate

Abstract

The influence of six different cooling rates on the microstructure of the liquid Cu₁₀Ag₉₀ alloy is investigated by molecular dynamics (MD) simulation. A newly developed topologically close-packed (TCP) method is used to conduct an extensive structural analysis for the crystalline and amorphous forms. It is found that the system exhibits an amorphous structure when the ratio of crystals to TCP clusters (R_c) is less than 1; otherwise, the structure is crystalline. The system is in the critical state of crystallization at the cooling rate 1 × 10¹¹ K s⁻¹ when R_c is close to 1. The conversion efficiency of TCP to crystal atoms is always at a lower level than other atoms. The crystal and TCP clusters have numerous interconnections, and the primary connections are divided into four types on the basis of the number of atoms, including 20 (I₂₀), 21 (I₂₁), 22 (I₂₂) and 23 (I₂₃) atoms. The lower average atomic energy TCP cluster phase inhibits the growth and formation of crystals by these interconnections because TCP contains more Cu atoms with lower energy than in the crystal form.