Cobalt-Free High-Entropy Alloys with Enhanced Strength-Ductility Synergy and Reduced Thermal Diffusivity

Area of Science:

• Materials Science
• Metallurgy
• Mechanical Engineering

Background:

• Developing advanced thermal barrier interlayers requires high mechanical strength, ductility, and low thermal diffusivity.
• Existing materials often face limitations in simultaneously meeting these stringent requirements.

Purpose of the Study:

• To design and investigate a low-cost, cobalt-free high-entropy alloy (HEA) for thermal barrier applications.
• To explore the relationship between microstructure, mechanical properties, and thermal diffusivity after annealing.

Main Methods:

• A cobalt-free V10Cr15Fe30Mn15Ni30 HEA was designed and processed via cold rolling (80% reduction).
• Annealing treatments were performed at temperatures ranging from 823 K to 1223 K for 30 minutes.
• Mechanical properties (tensile strength, elongation) and thermal diffusivity were evaluated.

Main Results:

• The annealed HEA exhibited an excellent strength-ductility synergy, with ultimate tensile strength exceeding 1 GPa and total elongation reaching 15%.
• All annealed samples demonstrated low thermal diffusivity.
• Quantitative analysis identified grain boundary and dislocation strengthening as dominant mechanisms below 1023 K, with grain boundary strengthening prevailing at higher temperatures.

Conclusions:

• The study successfully developed a cobalt-free HEA with enhanced mechanical properties and reduced thermal diffusivity.
• Leveraging sigma-phase precipitation and optimizing precipitate-matrix interfaces are key strategies for improving mechanical enhancement and thermal barrier functionality.
• The findings provide insights into tailoring HEAs for demanding thermal barrier applications.