Microstructural, magnetic, and geometrical thermodynamic investigation of FeCoNi(MnSi)x (0.0, 0.1, 0.25, 0.5, 0.75, 1.0) high entropy alloys

In the current investigation, FeCoNi(MnSi)x (x=0.0,0.1,0.25,0.5,0.75,1.0) high entropy alloys (HEAs) were effectively processed by mechanical alloying (MA) route. The impact of Mn and Si on the FeCoNi system was further analyzed based on structural, morphological, and magnetic properties utilizing X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM) at various processing stages. The results showed the formation of the Fe-rich BCC (major) + Ni-rich FCC (minor) phase in FeCoNi(MnSi)x (x=0.0,0.1,0.25) alloys however the Ni-rich FCC phase was significantly more recognizable in the case of FeCoNi(MnSi)x (x=0.5,0.75,1.0) HEAs. Furthermore, different symmetrical and asymmetrical geometrical thermodynamic models such as Muggianu, Lück chou, Kohler, Colinet, Hillert, Toop, and General solution model (GSM) were modeled using the Redlich-Kister formalism and then correlated the enthalpy value with the developed phases during MA. In the case of the GSM model, the enthalpy of mixing (ΔHmixGSM) was found to be negative in a whole concentration range of (MnSi)x at 1237 K and exhibited solid solution criteria confirmed from the enthalpy of mixing (ΔHmixMiedema) according to the Miedema model. Moreover, the associated activity coefficient (γa) revealed a negative deviation as Mn-Si content increased. Additionally, the magnetic properties showed a ferromagnetic nature, and its parameters were calculated from the "law of approach to saturation."