Effect of Ti on structure and soft magnetic properties of Si-rich Finemet-type nanocrystalline Fe73.5Cu1Nb3-xSi17.5B5Tix alloys

Highlights: • Substitution of Nb by Ti can reduce the T_x1 and enlarge the ΔT_x. • Fe_73.5Cu₁Nb₂Si_17.5B₅Ti₁ alloy exhibits high μ_i of 18,000 and low H_c of 0.54 Oe. • Magnetic properties were analysed in terms of the relationship between H_c and μ_i. • Soft magnetic properties will deteriorate when Nb is completely replaced by Ti. • The reasons of variation of permeability at high temperature were analyzed. - Abstract: Fe_73.5Cu₁Nb_3-xSi_17.5B₅Ti_x (x = 0, 1, 2, 3) amorphous alloys were prepared by the single roller melt spinning method. The effects of Ti substitution for Nb on the crystallization behavior, microstructure and soft magnetic properties were investigated. Compared to the previously reported Finemet alloy, the onset primary crystallization temperature T_x1 becomes lower which has dropped from 803K to 758K. The crystallization temperature interval ΔT_x increases from 468K to 488K as the x increases from 0 to 3. However, the Curie temperature of amorphous phase shows a downward tendency with the increase of Ti content. Compared to the previously reported Finemet alloy, the μ_i increases obviously to more than 18,000 at x = 1, the H_c decreases from 0.59 Oe to 0.54 Oe. When Ti replaces Nb completely, the optimum annealing temperature range for precipitating single soft magnetic phase is enlarged, but the permeability at room- and high-temperature is deteriorated, the reason of which was also analysed.