Structure and coercivity of nanocrystalline Fe-Si-B-Nb-Cu alloys

Srivastava

et al. 2010

Metall Mater Trans A

Self Cite

Melt-spun ribbons of Fe 99-x-y Zr x B y Cu 1 alloys with x + y = 11 and x + y = 13 were prepared under similar experimental conditions and characterized for structure and soft magnetic properties. Substitution of Zr by B changes the structure of as-spun ribbons from completely amorphous to cellular bcc solid solution coexisting with the amorphous phase at intercellular regions and then to completely dendritic solid solution. The glass forming ability (GFA) of the Fe-Zr-B-Cu system, evaluated from thermodynamic properties such as enthalpy of mixing and mismatch entropy, is found to be in good agreement with the experimental observations. Annealing of all ribbons leads to the precipitation of nanocrystalline bcc a-Fe phase from both amorphous phase and already existing bcc solid solution. A window of alloy compositions that exhibit the best combination of soft magnetic properties (high saturation magnetization and low coercivity) was identified.

Section: Discussionmentioning

confidence: 99%

Structure, Properties, and Glass Forming Ability of Melt-Spun Fe-Zr-B-Cu Alloys with Different Zr/B Ratios

Babu

Srivastava

et al. 2010

Metall Mater Trans A

Self Cite

“…Amorphous ribbons were produced using a vacuum melt spinner by remelting 30 g alloy in a quartz crucible whose bottom is in the form of a slit nozzle with rectangular cross section (10 mm 9 0.5 mm) and ejecting onto a rotating Cu wheel (300 mm diameter). Because the ambient condition has practically no effect on the structure, thermal stability, and magnetic properties of these alloys, [14] all experiments were carried out in air. The following parameters were varied systematically (within the range given in bracket), one at a time keeping other parameters constant:…”

Section: Methodsmentioning

confidence: 99%

“…[13] Detailed investigations were carried out to optimize the structure and soft magnetic properties of Fe-Si-B-Nb-Cu alloys with respect to the composition and process parameters. [14] The kinetics of nanocrystallization have also been studied for the alloys of different compositions. [15,16] The current investigators have observed that amorphous phase forms in the alloy of Fe 68.5 Si 18.5 B 9 Nb 3 Cu 1 composition even at a wheel speed as low as 12 m/s reveal a better glass-forming ability compared with other compositions.…”

Section: Introductionmentioning

confidence: 99%

Effect of Planar Flow Melt Spinning Parameters on Ribbon Formation in Soft Magnetic Fe68.5Si18.5B9Nb3Cu1 Alloy

Srinivas

Phanikumar

et al. 2011

Metall Mater Trans B

Self Cite

The effect of planar flow melt spinning (PFMS) parameters on the continuity, surface quality, and structure of 10-mm-wide Fe 68.5 Si 18.5 B 9 Nb 3 Cu 1 ribbons has been investigated. The change in shape and stability of the melt puddle as a function of the processing parameter was studied using a high-speed imaging system and was correlated to ribbon formation. A window of process parameters for obtaining continuous ribbons with good surface quality has been evaluated. It has been observed that thinner ribbons are found to be more continuous because of higher ductility. The higher melt temperature leads to the formation of crystalline phase in as-spun ribbons, and this deteriorates the soft magnetic properties on annealing. The experimental results are corroborated with the numerical estimates, which suggest that the critical thickness for amorphous phase formation decreases with increasing initial melt temperature.

“…Detailed experimental conditions for the preparation of rapidly solidified ribbons have been reported earlier. [14] As-spun ribbons were sealed in a quartz tube under vacuum (2 9 10 À5 mbar) and annealed at different temperatures (773 K (500°C) to 873 K (600°C)) for 1 hour.…”

Section: Methodsmentioning

confidence: 99%

Influence of Melt-Spinning Parameters on the Structure and Soft Magnetic Properties of (Fe0.65Co0.35)88Zr7B4Cu1 Alloy

Babu

Srivastava

et al. 2010

Metall Mater Trans A

Self Cite

Melt-spun ribbons of (Fe 0.65 Co 0.35 ) 88 Zr 7 B 4 Cu 1 alloy have been prepared at different wheel speeds, namely, 47, 39, 34, and 17 m/s, and subsequently annealed at 773 K (500°C) under controlled atmosphere. Structural and soft magnetic properties have been evaluated using X-ray diffraction, differential scanning calorimetry, transmission electron microscopy, and vibrating sample magnetometer. The structure of as-spun ribbons changes from fully amorphous to partially amorphous/nanocrystalline to fully nanocrystalline (bcc a-Fe(Co) + Fe 2 Zr) on decreasing the wheel speed. Annealing of amorphous ribbons leads to the precipitation of nanocrystalline bcc a-Fe(Co) phase. The Curie temperature (T c ) of the amorphous phase is found to increase with decreasing wheel speed possibly due to the effect of exchange field penetration of nanocrystals present in the amorphous matrix. The saturation magnetization (4pM s ) of as-spun ribbons having partially nanocrystalline bcc a-Fe(Co) phase is high as compared to the ribbons with completely amorphous phase, and it remains almost the same even after annealing. The lowest coercivity has been achieved in the ribbons that are fully amorphous, and the coercivity was found to increase with decreasing wheel speed.