Mithun Palit

Microstructure and magnetostriction of Tb0.3Dy0.7Fe1.95 prepared under different solidification conditions by zoning and modified Bridgman techniques

An intermetallic compound of nominal composition Tb0.3Dy0.7Fe1.95 was conventionally cast in the form of cylindrical rods of 8mm diameter and directionally solidified by zoning at three different growth rates. Compounds of the same nominal composition were also directionally solidified in the form of cylindrical rods of 20mm diameter by modified Bridgman technique, at two different growth rates. The microstructure of the directionally solidified compounds has been investigated as a function of solidification rate and compared with that of conventionally cast compound. The observed microstructural features of these samples have been correlated with the magnetostriction measured on the corresponding samples. Further, by examining the longitudinal sections cut along its cylindrical axis, a correlation of microstructure with magnetostriction has been brought out for each directionally solidified sample as a function of distance from the initially solidified end to the other. It has been observed that a large ...

Microstructure and magnetostriction of melt-spun Fe73Ga27 ribbon

Melt spun ribbon of Fe73Ga27 was prepared and characterized for microstructural features and magnetostriction. The phase equilibria observed from structural investigations have been correlated with Mossbauer studies. The magnetostriction of the melt spun ribbon has been found to be significantly large compared to the bulk sample. The large magnetostriction is attributed to the absence of ordered fcc (L12) phase in the melt spun ribbon, which is otherwise seen in slow cooled bulk Fe73Ga27 alloy.

Magnetic anisotropy and microscopy studies in magnetostrictive Tb-(Fe,Co) thin films

This paper reports the effect of the film thickness on the magnetostrictive behavior of (Fe,Co) rich Tb-(Fe,Co) films grown on Si ⟨100⟩ by electron beam evaporation. Magnetostriction was found to decrease with an increase in film thicknesses. To understand the variation of magnetostriction with the film thickness, detailed structural, microstructural, magnetization, and magnetic microscopy studies were carried out. X-ray diffraction studies indicated the presence of two phases, viz., Tb2 (Fe, Co)17 and Fe-Co phases, for all the films. With the increase in the film thickness, the peak intensity of the Tb2 (Fe, Co)17 phase decreased and that of the Fe-Co phase increased. Magnetization studies showed the presence of strong in-plane anisotropy for all the films. In addition to this, the presence of the out-of-plane component of magnetization was also observed for the films grown with higher thicknesses. This anisotropic behavior was also validated through magnetic microscopy studies carried out along the in-plane and out-of-plane directions employing magneto-optic Kerr microscopy and magnetic force microscopy, respectively. The decrease in magnetostriction was explained on the basis of dual phase formation and complex interplay between the in-plane and out-of-plane magnetic anisotropies present in the film.

Effect of B on the microstructure and magnetostriction of zoned Dy0.7Tb0.3Fe1.95

It had been reported that B has beneficial effects on the magnetostriction of anisotropy compensated Dy0.7Tb0.3Fe2 alloys. In the present work, Dy0.7Tb0.3Fe1.95 and Dy0.7Tb0.3Fe1.95Bx (x=0.1, 0.15, and 0.2) alloys, in the form of 8mm diameter cylindrical rods, were investigated both in the as-cast and zoned conditions. At 5kOe dc magnetic field, magnetostriction of ∼1200 and 900 microstrains was observed for zoned samples with x=0 and 0.1, respectively. For zoned samples with x>0.1 and for the as-cast sample of the parent alloy, magnetostriction of ∼500 microstrains was measured. X-ray diffraction of the zoned x=0 and x=0.1 samples showed a strong prevalence of the ⟨112⟩ and the ⟨110⟩ grain orientations; in contrast, the other samples appeared to possess a random grain orientation. Optical and scanning electron microscopy studies revealed a significant increase in the volume fraction of the RFe3 phase with increasing boron content. This increase in the volume fraction of the (Tb,Dy)Fe3 phase and the reduc...

Design and fabrication of Tonpilz type acoustic transducer using grain oriented Tb-Dy-Fe magnetostrictive material

A Tonpilz type transducer has been designed and fabricated using grain oriented Tb0.3Dy0.7Fe1.95 magnetostrictive rods as active elements. The design include provisions for DC biasing of the active elements with the help of an array of resin-bonded Nd-Fe-B ring magnets, AC drive coil and a pre-stressing mechanism. Resonance frequency of this transducer was found to be 1.6 kHz. A Transmitting Current Response (TCR) of 167 dB ref 1μPa/A at 1 m and a Transmitting Power Response (TPR) of 152 dB ref lμPa/W were achieved. The Source Level (SL) was determined to be 177 dB ref μPa at 1m.

Investigation on the Microstructure, Texture and Magnetostriction of Directionally Solidified Alloys

Effect of V addition on the microstructure and magnetostriction of directionally solidified Tb0.3Dy0.7Fe1.95 has been investigated. The microstructure of V added alloys (Tb0.3Dy0.7 with , 0.025, 0.05, and 0.075) indicate that Fe-50 at.% V is formed as primary phase, which subsequently undergoes spinodal decomposition. The spinodially decomposed Fe-rich phase reacts with the liquid and forms the matrix phase, (Tb,Dy)Fe2. The V-rich spinodally decomposed product, on the other hand, exists as remnant phase without undergoing any metallurgical transformation. Texture studies indicate that the grains of (Tb,Dy)Fe2 show /rotated and orientations for all compositions investigated in the directionally solidified condition. An improvement in magnetostriction has been noticed for small addition of V and with further addition the magnetostrictive property decreases. The formation of additional phases containing vanadium is attributed to be the reason when V is added in higher concentration levels.

Favorable Effect of Ho Addition on the Microstructure and Magnetostriction of Textured Tb0.3Dy0.7Fe1.95

This paper reports the effect of Ho on the microstructure, texture and magnetostrictive properties of Tb0.3Dy0.7-xHoxFe1.95 (with x = 0, 0.05, 0.1, 0.15 and 0.2) alloys. The alloys were vacuum induction melted and directionally solidified by modified Bridgman technique. Ho addition has been found to improve the magnetostriction at lower concentration due to absence of deleterious pro-peritectic (Tb,Dy)Fe3 phase. The static strain co-efficient is found to be better in Ho added alloys and the prevalence of strong and texture is attributed to be the reason.

Evolution of Texture during Directional Solidification of Giant Magnetostrictive Tb0.3Dy0.7Fe1.95 Alloy

The development of preferred grain orientation has been investigated in the directionally solidified samples of Tb0.3Dy0.7Fe1.95 as a function of pulling speed viz. 10, 40, 70 and 100 cm/h. The study indicates that at lower solidification rate (10 cm/h) growth of and texture components are preferred, whereas, texture component becomes dominant at higher pulling rate (100 cm/h). However, as the solidification progresses, growth of texture component is observed subduing the other components. Consequently, the magnetostriction improves from 1100 to 1350 micro-strains with higher pulling speed.

Structural And Magnetic Properties Of Ho1−xTbxFe1.95[x = 0.0,0.25, 0.5, 0.75 And 1.0]

Alloys of Ho1−xTbxFe1.95 [x = 0, 0.25, 0.5, 0.75 and 1] were prepared and investigated for the structural and magnetic properties. A three phase microstructure consisting of Laves phase (Ho,Tb)Fe2 as matrix, and (Ho,Tb)Fe3 and (Ho,Tb)‐rich as minor phases has been observed for alloys x>0.5. For alloys x⩽0.5, the (Ho,Tb)Fe3 phase is non‐existent. The lattice parameter and Curie temperature of the alloys are found to increase with Tb addition. At ambient condition, the easy magnetization direction lies along 〈100〉 for HoFe1.95 (x = 0) and changes to 〈111〉 for Tb substituted alloys [x = 0.25–1].

Structural And Magnetic Properties Of Dy0.7Tb0.3Fex [x = 2, 3]

Alloys of Dy0.7Tb0.3Fex [x = 2, 3] were prepared and investigated for structural and magnetic properties. A three phase microstructure consisting of (Dy,Tb)Fe2, (Dy,Tb)Fe3 and (Dy,Tb)‐rich phases were found for the alloy x = 2, whereas a two phase microstructure consisting of (Dy,Tb)Fe3 and (Dy,Tb)6Fe23 was found for the alloy x = 3. The saturation magnetization, Curie temperature and the magnetostriction were found to be lower for the Fe‐rich alloy (x = 3) as compared to the alloy x = 2. The anisotropy also was found to be lower for x = 3 which explains the reason for lower magnetostriction.