Microstructure of Liquid Co₅₀Ni₅₀ During Rapid Solidification

Area of Science:

• Materials Science
• Computational Materials Science
• Solidification Science

Background:

• Understanding alloy solidification is crucial for developing advanced materials.
• Rapid solidification processes influence the final microstructure and properties of alloys.
• Cobalt-Nickel (Co50Ni50) alloys are important for various industrial applications.

Purpose of the Study:

• To investigate the cluster structure formation and evolution during rapid solidification of Co50Ni50 alloy.
• To analyze the dominant bond types and crystalline structures formed.
• To elucidate the relationship between transient crystalline (TCP) structures and the final face-centered cubic (fcc) phase.

Main Methods:

• Molecular dynamics (MD) simulations were employed to model the rapid solidification process.
• Pair distribution function analysis was used to study atomic arrangements.
• Honeycutt-Andersen bond type analysis identified local atomic structures.
• Largest standard cluster analysis quantified structural evolution.

Main Results:

• Co-Co bonds formed with higher probability than Ni-Ni bonds during solidification at 1x10^12 K/s.
• The 1421 bond type was dominant, leading to a primary face-centered cubic (fcc) structure.
• Hexagonal close-packed (hcp) and body-centered cubic (bcc) structures were also observed in smaller proportions.
• Formation of the fcc structure necessitated the prior decomposition of transient crystalline (TCP) structures around 1450 K.

Conclusions:

• The study provides insights into the atomic-level mechanisms governing rapid solidification of Co50Ni50 alloys.
• The dominance of the 1421 bond type and the fcc structure is confirmed.
• The critical role of TCP structure decomposition for fcc formation under rapid cooling is highlighted.
• Findings offer guidance for experimental control of Co50Ni50 alloy crystallization.