Effect of Aluminum Addition on the Microstructure, Magnetic, and Mechanical Properties of FeCrCoNiMn High-Entropy Alloy

High-entropy FeCoCrNiMn (C1) and FeCoCrNiMn10Al10 (C2) alloys (HEAs) were mechanically alloyed for 24 h and heated to 900 degrees C (C1_900 degrees C and C2_900 degrees C). The powders were also compacted into pellets (C1_pellet and C2_pellet) and sintered at 500 degrees C for 1 h. Crystal structure, microstructure, magnetic, and mechanical properties were investigated by X-ray diffraction, scanning electron microscopy, vibrating sample magnetometry, and microindentation. During the milling process, a mixture of body-centered-cubic (BCC) and face-centered-cubic (FCC) phases with a crystallite size in the range of 9-13 nm was formed in the C1 HEA alloy. The dual FCC + BCC solid solutions remain for the C1_pellet and transform to a single FCC for the C1_900 degrees C powders. Al addition stabilizes the BCC structure in the FeCoCrNiMn10Al10 HEA alloy, as revealed by the structural refinement. The structure exhibits a mixture of BCC + FCC solid solutions for the C2 powders and BCC + FCC + CrCo sigma phase for the C2_pellet and C2_900 degrees C powders. The crystallite sizes are in the range of 6-93 nm for all the samples. The saturation magnetization (Ms), coercivity (Hc), and squareness ratio (Mr/Ms) are estimated to be 24.2 emu/g, 153.62 Oe, and 0.165, respectively, for C1 and 28.45 emu/g, 188.48 Oe, and 0.172 for C2. The C1_900 degrees C and C2_900 degrees C powders exhibit, respectively, paramagnetic and soft magnetic behaviors and an exchange bias at room temperature. The C1_pellet and C2_pellet HEAs show high hardness values of 584.85 Hv and 522.52 Hv, respectively.

Automated summary

By performing mechanical alloying and high temperature treatment, the crystal structure, microstructure, magnetic, and mechanical properties of high-entropy alloys (HEAs) can be manipulated. The addition of different alloying elements can stabilize or alter the phase structure of the alloy, thereby influencing its magnetic and hardness properties.