Pseudo-single crystals of Terfenol-D were grown by the cold-crucible Czochralski technique from the nominal compositions of Tb_(0.27)Dy_(0.73)Fe_x and Tb_(0.3)Dy_(0.7)Fe_x (x=1.9, 1.95). The as-grown boules consist of a few well aligned grains with growth direction close to <112> orientation. Both twin boundaries and needle-shaped Widmanstatten precipitates arranged in a crystallographic orientation have been observed. The density of the twins and Widmanstatten precipitates are found to vary with the composition of the start alloys. Detailed microstructural study reveals the existence of many {111} plane stacking faults and numerous interfacial dislocations around the coherent Widmanstatten phases. The density of the stacking faults shows little variation between crystals with different compositions, but depends on the growth rates. Compositional analysis by X-ray wave length dispersive analysis on SEM shows that the as-grown crystals have the iron content shifted towards stoichiometry, RFe_2 (where R stands for rare earth), but the ratio of Tb/Dy was unchanged.Magnetomechanical coupling coefficient (k_(33)) measurement on a Czochralski-grown rod sample shows potentially higher coefficient than samples prepared by other routes. The presence of the Widmanstatten precipitates, twin boundaries and stacking faults strongly degrade the magnetostrictive properties of the crystals by pinning the domain wall rotation. The influence of the microstructural variation of samples prepared with different nominal composition on the magnetostrictive properties is discussed.
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