Processing-driven chemical ordering and its effect on magnetic properties in a high entropy alloy

Area of Science:

• Materials Science
• Magnetism
• Physical Metallurgy

Background:

• High entropy alloys (HEAs) offer tunable properties for advanced applications.
• Understanding the interplay between microstructure and magnetic behavior in HEAs is crucial for material design.

Purpose of the Study:

• To investigate the influence of chemical ordering and its length scale on the magnetic behavior of Al$_{0.2}$Ti$_{0.3}$Co$_{1.5}$CrFeNi$_{1.5}$ HEA.
• To correlate microstructural evolution with magnetic properties across different processing conditions.

Main Methods:

• Altering microstructural conditions through solution annealing, annealing at 750 °C, and cold rolling plus annealing.
• Characterizing precipitate evolution (volume fraction, size, morphology) and phase formation (L1$_{2}$, L2$_{1}$).
• Conducting magnetic measurements from 2 K to 300 K to determine saturation magnetization, coercivity, and magnetic transition temperatures.

Main Results:

• Solution annealed condition showed a single magnetic transition near 48 K with low coercivity, linked to fine L1$_{2}$ precipitates.
• Annealed and cold-rolled conditions exhibited a second, lower-temperature magnetic transition due to L1$_{2}$ phase coarsening and decoupling.
• Increased coercivity in processed conditions attributed to domain wall pinning and L2$_{1}$ phase presence.

Conclusions:

• Chemical ordering and microstructural evolution are key determinants of low-temperature magnetic behavior in this HEA system.
• Tailoring processing routes allows for control over magnetic properties in multifunctional HEAs.
• Findings advance the understanding of magnetic HEAs with potential for combined magnetic and mechanical performance.