Orientation Selection and Microstructural Evolution in Directionally Solidified Tb0.3Dy0.7Fe1.95

Abstract

Tb 0.3 Dy 0.7 Fe 1.95 alloy was directionally solidified by using a modified Bridgman technique at a wide range of growth rates of 5 to 100 cm/h. The directionally grown samples exhibited plane front solidification morphology up to a growth rate of 90 cm/h. Typical island banding feature was observed closer to the chilled end, which eventually gave rise to irregular peritectic coupled growth (PCG). The PCG gained prominence with an increase in the growth rate. The texture study revealed formation of strong h311i texture in a lower growth rate regime, h110i and ''rotated h110i'' in an intermediate growth regime, and h112i in a higher growth rate regime. In-depth analysis of the atomic configuration of a solid-liquid interface revealed that the growth texture is influenced by the kinetics of atomic attachment to the solid-liquid interface, which is intimately related to a planar packing fraction and an atomic stacking sequence of the interfacial plane. The mechanism proposed in this article is novel and will be useful in addressing the orientation selection mechanism of topologically closed packed intermetallic systems. The samples grown at a higher growth rate exhibit larger magnetostriction (k) and dk/ dH owing to the absence of pro-peritectic (Tb,Dy)Fe 3 and formation of h112i texture, which lies closer to the easy magnetization direction (EMD).

Recent Advances in Magnetostrictive Tb-Dy-Fe Alloys

“…By comparing the texture at different distances from the onset of solidification, Palit et al [20] found that the transition in the preferred growth direction from <110> to <112> occurred through intermediate <123> texture components. Furthermore, plane-front solidification morphology and irregular peritectic coupled growth were observed in a wide range of solidification rates (5-80 cm/h), while the preferred direction changed from <311> to <110> to <112> at 5-100 cm/h solidification rates [21]. The {111} planes in Figure 2a were composed of two different types of atomic layers, in which one layer was all Fe, which increased the obstacle of atomic arrangement in the growth process.…”

“…Figure 2. Comparison of atomic attachment kinetics at (a) (111) and (b) (311) interfaces; (c) magnetostriction (λ) of directionally solidified samples measured at an applied field of 5 kOe and (d)the plot of slope (dλ/dH) of the initial λ-H plot, plotted as a function of growth rate[21] (Adapted with permission from Ref [21]…”