Effects of annealing and cold rolling on microstructural features, magnetic properties, tensile behavior and electrical resistance of FeCoNi(MnAl)x high entropy alloys

Abstract

In this study, the microstructure, magnetic properties, and tensile behavior of high entropy alloys of FeCoNi(MnAl)_x (x = 0–0.6, in molar ratios) were investigated after casting, cold rolling and annealing. X-ray diffractometry (XRD), field emission scanning electron microscope (FE-SEM), vibrating sample magnetometer (VSM), and also tensile tests were used to evaluate phase formation, microstructure, magnetic behavior and tensile properties of the samples, respectively. The results showed that as the indices of x value increase to 0.6, crystallographic structures transform from FCC to FCC + BCC. This in turn decreased the magnetic saturation of FeCoNi(MnAl)_0.6 from 151 to 36 emu/g. Increasing x to 0.6, also raised the values of Hc from 3 to 16 Oe. This behavior was also observed in annealed and cold rolled alloys. Annealing treatment also released the residual stresses and resulted in reduction of Hc values. However, the highest values of Hc was observed in cold rolled samples which ranged from 5 to 25 Oe. The tensile strength of cold rolled and annealed alloys for x values of 0, 0.2, and 0.4, were 510, 635, and 910 Mpa, respectively. Furthermore, the electrical resistance augmented monotonously with an increasing value of x. It is therefore concluded that cold rolled and annealed high entropy alloys of FeCoNi(AlMn)x can present a variety combinations of tensile, magnetic, and electrical behavior when compared to other soft magnetic materials.