Phase Relationship and Magnetostriction of Tb–Dy–Ho–Fe Alloys
The phase relationship of Tb<sub>0.26</sub>Dy<sub>0.49</sub>Ho<sub>0.25</sub>Fe<sub>x</sub> (1.6 ≤ × ≤ 2.4) alloys in the Tb-Dy-Ho-Fe system was determined by using optical microscopy, X-ray diffraction, and differential thermal analysis. The vertical section of Tb<sub>0.26</sub>Dy<sub>0.49</sub>Ho<sub>0.25</sub>Fe<sub>x</sub> alloys consists of two single-phase regions, namely, L (liquid) and (Tb, Dy, Ho)Fe<sub>2</sub>, and four two-phase regions, namely, L + (Tb, Dy, Ho)Fe<sub>3</sub>, L + (Tb, Dy, Ho)Fe<sub>2</sub>, (Tb, Dy, Ho)Fe<sub>2</sub> + (Tb, Dy, Ho)Fe<sub>3</sub>, and (Tb, Dy, Ho)Fe<sub>2</sub> + (Tb, Dy, Ho). The range between the liquidus and peritectic temperatures for Tb<sub>0.26</sub>Dy<sub>0.49</sub>Ho<sub>0.25</sub>Fe<sub>x</sub> alloys becomes narrow with addition of Ho, which is beneficial to decrease the properitectic (Tb, Dy, Ho)Fe<sub>3</sub> phase. The magnetic field dependence of magnetostriction (λ<sub>//</sub>, λ<sub>⊥</sub>) for Tb<sub>0.26</sub>Dy<sub>0.49</sub>Ho<sub>0.25</sub>Fe<sub>x</sub> alloys has been determined. The magnetostriction quickly increases with increasing magnetic field value when it is less than 240 kA/m. Among the present studied alloys, the sample with x = 1.9 possesses the largest magnetostriction. It has been found that magnetic annealing improves the magnetostriction λ<sub>//</sub> of Tb<sub>0.26</sub>Dy<sub>0.49</sub>Ho<sub>0.25</sub>Fe<sub>1.9</sub> alloy.