Effects of elemental addition on the microstructure, thermal stability, and magnetic properties of the mechanically alloyed FeSiBAlNi high entropy alloys

• FeSiBAlNi (Co, Cu, Ag) amorphous high entropy alloys (HEAs) were fabricated by MA.
• Co addition remarkably enhances the glass forming ability and thermal stability.
• Ag addition induces composite formation with amorphous and FCC solid solution.
• As-milled FeSiBAlNi (Co, Cu, Ag) HEAs possess semi-hard magnetic property.
• The coexistence of FCC and BCC phases promotes the high semi-hard magnetism of HEAs.

The effects of element addition, Co, Cu, and Ag on the microstructure, thermal property and magnetic properties of mechanical alloyed FeSiBAlNi high entropy alloys (HEAs, base alloy) have been investigated in depth in the present work. The FeSiBAlNi (Co, Cu, Ag) amorphous HEAs have been successfully fabricated by mechanical alloying process. The results reveal that Co and Cu additions obviously shorten the formation time of fully amorphous phase, therefore, leading to enhanced glass forming ability of the base alloy. The final milling product of FeSiBAlNiAg consists of amorphous phase and nanocrystals with face-centered cubic (FCC) structure. In addition, Co addition obviously improves the thermal stability of the base alloy, while Cu and Ag additions present the detrimental effects. Moreover, the as-milled HEAs exhibit the semi-hard magnetic property. However, the saturation magnetization (Ms) values become decreased with element additions. It suggests that the coexistence of FCC and body-centered cubic (BCC) phase gives rise to a higher Ms than a single amorphous phase or mixture of amorphous and FCC phases. Additionally, the phase formation mechanisms of amorphous and solid solution phases, as well as the correlation between the microstructure and magnetic properties have been discussed, which can be beneficial to the design of novel alloy systems.

The amorphous structure of 140 h as-milled FeSiBAlNi(Co, Cu) HEAs and the amorphous composite with FCC of 140 h as-milled FeSiBAlNiAg HEAs can be clearly observed from the TEM, SAED and HRTEM images.Figure optionsDownload as PowerPoint slide