Effect of Fe addition on the crystallization behaviour and Curie temperature of CoCrSiB-based amorphous alloys

Abstract

The crystallization behaviour and Curie temperature of melt-spun Co 71Àx Fe x Cr 7 Si 8 B 14 (x ¼ 0, 2, 3.2, 4, 6, 8 and 12 at.%) amorphous alloys have been studied. Differential scanning calorimetry (DSC) showed two stages of crystallization. The first stage of crystallization (T X1 ) in the alloy with 6 at.% Fe was the highest and it had the highest activation energy. X-ray diffraction studies revealed that the primary crystalline phase is hcp-(CoCr) 2 Si for Fe-free alloy, whereas (CoFeCr) 2 Si and (CoFeCr) 3 Si phases were formed with the addition of Fe. hcp-Co was also formed along with these phases. The secondary crystalline phases were fcc-Co and various boron-rich phases. The Curie temperature of the alloys also changed with the addition of Fe to the system. Like the primary crystallization temperature, the Curie temperature of the alloys did not vary systematically with the Fe content. The addition of Fe to the Co-based system changes the nearest-neighbour interaction. This changes the exchange interaction between the transition metal elements. Due to the asymmetry in the Bethe-Slater curve, a systematic variation with Fe addition was not observed in the Curie temperature measurement.

Development of Co-Rich Microwires with Graded Magnetic Anisotropy

“…The crystallization, T cr , and Curie, T c , temperatures of the studied microwires, evaluated by the DSC method as described elsewhere [ 66 ], were about 510 and 370 °C, respectively. T cr and T c , values are consistent with the values observed in CoFeCrSiB microwires [ 46 ] and ribbons [ 67 , 68 ] with similar compositions. Consequently, like other Co-rich stress-annealed microwires, the studied microwires annealed at T ann ≤ 300 °C retain amorphous structure after stress-annealing [ 47 , 48 , 49 ].…”

Crystallisation Kinetics of Co75-xMxSi15B10(M = Fe, Mn, Cr and x=0, 5) Amorphous Alloys

“…The value of x at any selected T is calculated from the ratio of the partial area (S) of the crystallization peak at the selected T to the total area (S 0 ) of the crystallization exotherm. Equation (7) indicates that at any fixed temperature, the crystallization mechanism, or the Avrami exponent n, can be obtained from the slopes of the ln(− ln(1 − x)) − ln(β) curves. The Avrami exponent n involves the information regarding the nucleation and growth mechanism in the crystallization process.…”

“…As can be seen from DTA measurements, although Mn substituted sample exhibits only one exothermic peak, the Fe and Cr substituted samples exhibit two distinct exothermic peaks. The presence of two exothermic peaks for Fe and Cr substituted samples could be interpreted as the formation of second crystallization phase and the crystallization process of the alloy proceeds through a multi-stage model [7,11,21]. The activation energy of the crystallization process gives important information regarding the thermal stability of the sample.…”

“…In recent years, Co-and Fe-based amorphous alloys and their crystallization kinetics have been extensively studied due to their excellent physical and mechanical properties, such as high electrical resistivity, small eddy currents, high thermal stability, high corrosion resistance, outstanding mechanical properties, low fabrication cost, and soft magnetic properties along with the ease of machining due to the disordered structure [1][2][3][4][5][6][7][8][9]. These properties also lead to improvements in their electrical and corrosion properties.…”

Electron transport properties of Co71−xFexCr7Si8B14 (x=0, 2, 3.2, 4, 6,8 and 12at%) amorphous alloys during devitrification

“…It is suggested that in this range, the magnon contribution arising out of Co-Co, Co-Fe and Fe-Fe exchange interaction is suppressed by electron-phonon scattering leading to lowering of Curie temperature. Such complex exchange interactions with relative Co-Fe stoichiometric variations have also been explained on the basis of their positions in Bethe-Slater curve [21].…”