Deformable Eutectic Alloy With Near-Theoretical Yield Strength via Hierarchical Nanoscale Multiphases and Sessile...

Area of Science:

• Materials Science
• Metallurgy
• Nanotechnology

Background:

• Eutectic high-entropy alloys (EHEAs) offer potential for high strength and ductility.
• Extreme modulus/hardness mismatch in EHEAs limits yield strength and causes premature fracture.
• Microstructure modification is key to overcoming these limitations in structural applications.

Purpose of the Study:

• To design and investigate a CoCrFeNiTa$_{0.4}$ EHEA with enhanced mechanical properties.
• To understand the mechanisms behind achieving high strength and ductility simultaneously.
• To explore the role of hierarchical nano-multiphase structures and interface defects.

Main Methods:

• Suction casting followed by precise thermal treatment to create the EHEA.
• Characterization of hierarchical nano-multiphase structures (FCC-Laves lamellae, L1$_{2}$ and D0$_{22}$ coprecipitates).
• Analysis of sessile interface defects and their impact on mechanical properties.

Main Results:

• Achieved a near-theoretical yield strength of 2.6 GPa with 13.6% plasticity.
• Demonstrated a reduced modulus/hardness mismatch between FCC and Laves phases.
• Identified strengthening mechanisms: coherent precipitates, sessile planar faults, and misfit-interface dislocations.

Conclusions:

• Hierarchical nano-multiphase structures and defects are crucial for high-performance EHEAs.
• Long-range modulus/hardness matching and short-range heterostructures enable theoretical strength with plasticity.
• This approach is pivotal for developing next-generation dual- and multi-phase alloys for structural applications.