STRUCTURAL AND MAGNETIC STUDY OF ACTIVE SCREEN PLASMA NITRIDED FE73:5SI13:5B9NB3CU1 AND FE77SI11B9NB2:4CU0:6RIBBONS

Abstract

The comparative study of Active Screen Plasma Nitriding (ASPN) treatment of two Finemet-type alloys with the compositions of Fe73:5Si13:5B9Nb3Cu1 and Fe77Si11B9Nb2:4Cu0:6 was investigated in dierent temperatures ranging from 410C to 560C. Dierential Scanning Calorimetry (DSC), X-Ray Diractometery (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), electrical resistivity, microhardness measurements and magnetic characterization by a Vibrating Sample Magnetometer (VSM) were utilized to characterize the treated samples. The comparison of the DSC data for the alloys suggested that the smaller amount of Nb as a growth inhibitor shifted the crystallization temperatures towards lower temperatures. Thus, the crystalline volume fraction and grain size in each temperature for Fe77Si11B9Nb2:4Cu0:6 alloy increased compared to Fe73:5Si13:5B9Nb3Cu1 alloy. The size of iron nitrides on the surface of the ribbons with the lower Si content was larger. The electrical resistivity for the annealed and nitrided Fe77Si11B9Nb2:4Cu0:6 alloy was lower compared to the annealed and nitrided Fe73:5Si13:5B9Nb3Cu1 alloy, due to the larger grain size and lower Si content of Fe(Si) phase in Fe77Si11B9Nb2:4Cu0:6 alloy. The VSM results showed that the maximum saturation magnetization and coercivity at 440C were obtained in Fe77Si11B9Nb2:4Cu0:6 alloy after nitriding under 75% H2 and 75% N2 gas mixture, respectively.