Decreasing the sensitivity of soft magnetic properties to heat-treatment process parameters by minor Nb alloying in Fe83C4B6.5P5.5Cu1 nanocrystalline alloys

To decrease the sensitivity of high -Bs Fe -based nanocrystalline soft magnetic alloys to heat -treatment process parameters and promote their engineering applications, the effect of Nb addition on the glass -formation ability (GFA), crystallization behavior, soft magnetic properties, and Fe3(B, P) compound phase stability in Fe83_xC4B6.5P5.5Cu1Nbx (x = 0, 0.15, 0.5, 1.0, and 2.0 at. %) alloys were systematically investigated. It was found that Nb addition did not decrease the GFA of this alloy system. Thermophysical analysis indicates that Nb addition has little effect on the first crystallization peak, but it can effectively increase the second crystallization peak, which increases from 785.2 K for the Nb-0 alloy to 803.4 K for the Nb-2.0 alloy. Analyzing the relationship among soft magnetic properties, structure, and heat -treatment process parameters, including annealing temperature (Ta), holding time, and heating rate, confirmed that Nb addition to this alloy system effectively delays the precipitation of the Fe3(B, P) compound phase and decreases the influence of heat -treatment process parameters on soft magnetic properties. The optimal Ta range increases from 50 K for the Nb-0 alloy to 100 K for the Nb-2.0 alloy, and the optimal holding time increases from 6 min for the Nb-0 alloy to 45 min for the Nb-2.0 alloy when annealing at 753 K. The heating rate decreases from the rapid heating for the Nb-0 alloy to 40 K/min for the Nb-2.0 alloy when the Ta = 753 K.