Influence of Si and Mn on the Phase Formation, Crystallization Kinetics, and Enhanced Magnetic Properties of Mechanically Alloyed NiCoFe(SiMn)x High Entropy Amorphous Alloys

Abstract

NiCoFe(SiMn)x high entropy amorphous alloys (HEAAs) were successfully prepared via mechanical alloying. The structural and magnetic properties were investigated by X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometer. Based on the structural analysis, a simple solid solution of α-BCC + γ-FCC phases were formed for x= 0.0 , 0.1 , whereas γ-FCC + amorphous phases were detected as Si and Mn content increases for x= 0.25 , 0.5 , 0.75 , 1.0 HEAAs. Furthermore, differential scanning calorimetry was used to examine the non-isothermal crystallization kinetics in the 35 h milled sample. The results showed that the HEAAs powder has two distinct exothermic crystallization peaks, which become much more prominent as Si and Mn content increases. The onset (Ex1, Ex2) and the apparent (Ep1, Ep2) activation energies were calculated using Kissinger's and Ozawa's equations. According to these equations Ex1 &gt

Ep1, Ex2 &gt

Ep2 for the proposed HEAAs, the nucleation process was more difficult than overcoming the energy barrier for the rearrangement of atoms and the grain growth process of crystallization. Meanwhile, local activation energies gave consistent results with the apparent activation energies. They estimated from the Kissinger–Akahira–Sunose, and Ozawa-Flynn-Wall models under non-isothermal conditions, revealing that both the exothermic peaks have higher values of local activation energies at the beginning of the crystallization process. In addition, the Johnson–Mehl–Avrami-Kolmogorov models were used to determine the Avrami exponents, indicating that the crystallization process becomes more accessible due to decreased local activation energies, leading to high-dimensional growth with an increasing nucleation rate. Moreover, a simple phenomenological model was also proposed based on the Lorentzian functions model evaluated on the first derivative of magnetic hysteresis loops. Graphical Abstract: [Figure not available: see fulltext.] © 2023, The Author(s), under exclusive licence to Springer Nature B.V.