Fe-Based Medium-Entropy Alloys: Metastability, Microstructure, Strengthening, and Service-Oriented Design

Area of Science:

• Materials Science
• Metallurgy
• Alloy Design

Background:

• Fe-based medium-entropy alloys (MEAs) are cost-effective alternatives to traditional high-entropy alloys.
• Metastable face-centered cubic (FCC) matrices in Fe-MEAs can achieve high strength and ductility through controlled transformation.

Purpose of the Study:

• To critically synthesize metastability, microstructure, and strengthening mechanisms in Fe-based MEAs.
• To emphasize integrated metastability engineering and microstructural design for application-specific development.
• To provide a service-oriented design framework for high-performance, low-cost Fe-based MEAs.

Main Methods:

• Literature review of peer-reviewed studies linking composition, processing, microstructure, and properties.
• Comparison of Fe-rich non-equiatomic alloy systems to understand regulation of metastability and precipitation.
• Emphasis on coordinated control of metastability, heterogeneous microstructures, and strengthening mechanisms.

Main Results:

• Superior properties in Fe-based MEAs result from coordinated control of metastability, heterogeneous microstructures, and strengthening mechanisms.
• Controlled transformation kinetics are crucial for sustained strain hardening and strength-ductility synergy.
• Alloying and processing effectively regulate metastability, precipitation, transformation kinetics, and strain partitioning.

Conclusions:

• Controlled transformation kinetics, rather than maximizing martensite, is the key design variable for Fe-based MEAs.
• Integrated control of composition, metastability, microstructure, and processing enables high-performance, low-cost Fe-based MEAs.
• Further research needed on coupled mechanisms, metastability prediction, stability, manufacturability, and computational alloy design.