Damascus-style hierarchical microstructures enable a strong and ductile medium-entropy alloy

Area of Science:

• Materials Science
• Metallurgy
• Nanotechnology

Background:

• Traditional alloys require energy-intensive processing for strength and toughness.
• High-entropy alloys (HEAs) and medium-entropy alloys (MEAs) present a sustainable alternative with tunable properties.
• Controlling atomic complexity is key to developing advanced alloys.

Purpose of the Study:

• To fabricate and characterize a novel Cu-Au-Ag MEA.
• To investigate the relationship between microstructural features and mechanical properties.
• To establish an efficient alloy design approach for high-performance electronic packaging.

Main Methods:

• Fabrication of Cu-Au-Ag MEA using vacuum suspension melting and heat treatment.
• Microstructural analysis revealing micron-scale phase separation, nano-ordered L12 phase, and chemical short-range order (CSRO).
• Mechanical testing (tensile and compressive) on micropillar and large-scale samples.
• High-temperature ternary alloy phase diagrams and simulations for validation.

Main Results:

• The Cu-Au-Ag MEA exhibited three distinct levels of heterogeneous structures.
• Micropillar samples showed 550 MPa tensile strength, 1700 MPa compressive strength, 25% tensile elongation, and >50% compressive strain.
• Large-scale samples achieved ~500 MPa tensile strength and 40% elongation.
• Enhanced strength and plasticity compared to traditional gold, silver, and copper alloys.

Conclusions:

• The developed MEA design approach effectively regulates multilayer heterogeneous structures through atomic affinity manipulation.
• The Cu-Au-Ag MEA demonstrates superior mechanical properties, making it suitable for demanding applications.
• This work provides an efficient pathway for designing advanced MEAs for electronic packaging.