Effects of Cr element doping on microstructure and performance of quinary FeCoNiSiB multi-principal element alloys

This research focused on the influences of Cr element doping on the microstructure, thermal stability, microhardness, soft magnetic, and anti-corrosion properties of FeCoNiSiB multi-principal element alloys. The as-received Fe-Co-Ni-Si-B-Cr alloy ribbons made by melt-spinning technique could maintain amorphous nature. The glass-transition temperature and onset crystallization temperature become lower with the addition of Cr, and the highest values are 782.0 K and 821.5 K, respectively. When the Cr content reaches 3at.%, the alloy owns the best soft magnetic performance with the saturation magnetic flux density of similar to 0.578 T and coercivity of similar to 5.5 A<middle dot>m-1 among the studied melt-spun ribbon samples. The microhardness of all alloy ribbons reduces with an increasing Cr content on the whole, and the values are 810 HV0.5 or above. The corrosion behavior of these multi-principal element amorphous alloys containing Cr was also investigated in detail. As the Cr content increases, the corrosion resistance becomes superior and the specimens present the obvious passive regions in 3.5wt.% NaCl solution. The glassy ribbons with 8at.% Cr have the highest self-corrosion potential of -0.340 V and pitting potential of 0.288 V as well as the widest passive region of 0.628 V. Besides, the corroded micrographs of alloy ribbons immersed in corrosive environment lasting 100 h are also presented, which further confirms the above-mentioned experimental results. This research deepens the understanding about the role of Cr element in the microstructure and a series of physical and chemical properties of Fe-Co-Ni-Si-B-Cr multi-principal element amorphous alloys.