Microstructure and Thermal Cyclic Behavior of FeNiCoAlTaB High-Entropy Alloy.

Area of Science:

• Materials Science
• Metallurgy
• Physical Metallurgy

Background:

• High-entropy alloys (HEAs) offer unique properties due to their multi-element composition.
• Understanding the relationship between microstructure and shape memory effect is crucial for HEA applications.
• Previous research has explored various compositions and processing routes for HEAs with shape memory characteristics.

Purpose of the Study:

• To investigate the impact of annealing time and aging treatment on the microstructure and shape memory properties of a specific HEA.
• To correlate changes in grain morphology, texture, and precipitation with magnetic and shape memory performance.
• To optimize processing parameters for enhanced recoverable strain in the Fe-Ni-Co-Al-Ta-B HEA.

Main Methods:

• Electron Backscatter Diffraction (EBSD) for texture analysis.
• Microstructural characterization of grain morphology and size.
• Thermo-magnetic analysis to determine austenite finish temperature.
• X-ray Diffraction (XRD) for phase identification and precipitate analysis.
• Three-point bending tests to evaluate shape memory properties (recoverable strain and stress-temperature slope).

Main Results:

• Annealing at 1300 °C for 1 hour resulted in larger grain sizes (504.6 μm) without strong texture, improving recoverable strain.
• Aging at 600 °C for 12-24 hours increased austenite finish temperature and led to precipitate formation.
• Maximum recoverable strain reached 3.6% for samples aged at 600 °C for 24 hours.
• A higher stress-temperature slope (10.3 MPa/°C) at 12 hours aging correlated with lower recoverable strain.

Conclusions:

• Optimized annealing and aging treatments are critical for tailoring shape memory properties in this HEA.
• Larger grain size and controlled precipitation enhance recoverable strain.
• The study provides insights into processing-microstructure-property relationships for shape memory HEAs.