In-Situ Imaging of Molten High-Entropy Alloys Using Cold Neutrons

Area of Science:

• Materials Science
• Metallurgy
• Neutron Imaging

Background:

• Previous studies observed liquid state immiscibility in equiatomic CoCrCu alloys using neutron imaging.
• Understanding liquid state behavior is crucial for developing advanced alloy systems.

Purpose of the Study:

• To investigate the in-situ remixing of immiscible liquids in equiatomic CoCrCuNi alloys.
• To observe the melting, alloying, and solidification processes in real-time using neutron imaging.
• To compare experimental observations with thermodynamic predictions.

Main Methods:

• Real-time neutron imaging was employed to capture radiographs during heating and cooling cycles.
• Equiatomic CoCrCu and Ni buttons were melted in an alumina crucible within a high-temperature vacuum furnace.
• Thermodynamic calculations of the CoCrCuNi isopleth were performed using the Thermo-Calc TCHEA3 database.

Main Results:

• Neutron imaging captured the transition from immiscible to miscible liquid states as Ni dissolved into the CoCrCu melt.
• Phase-separated liquids were observed to remix into a single-phase liquid.
• Experimental results showed good agreement with thermodynamic calculations, indicating single-phase liquid solidification.

Conclusions:

• Neutron imaging is a powerful technique for observing real-time liquid state phase changes in metals.
• The addition of Ni to CoCrCu promotes remixing of immiscible liquids into a single-phase liquid.
• The CoCrCuNi alloy solidifies from a single-phase liquid, consistent with thermodynamic predictions.