Order-disorder phase transitions in Fe81Ga19-RE ALLOYS (RE = Dy, Er, Tb, Yb) according to neutron diffraction data

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Resumo

New data on the phase compositions and structural transformations in a number of Fe81Ga19 alloys doped with trace amount (≤ 0.2 at.%) of rare earth elements are presented. The data are obtained in neutron diffraction experiments performed with high resolution and in continuous temperature scanning mode when heated to 900 °C and subsequent cooling. It has been established that structural rearrangements proceed in a generally identical manner both in the original Fe81Ga19 alloy and in its doped analogues. Slow heating and subsequent cooling of the alloys (rate ±2 °C/min) leads to the formation of clusters of the D03 phase with sizes in the range (200–300) Å in the matrix of the disordered A2 phase. The sizes and volume fraction of clusters (~0.3 of the sample volume) weakly depend on the specific composition. The degree of ordering of the clusters atomic structure changes with temperature according to a second-order phase transition and is close to unity at room temperature. The search for structural ordering corresponding to the modified D03 phase, discovered in a number of electron diffraction studies, did not lead to a positive result.

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Sobre autores

A. Balagurov

Joint Institute for Nuclear Research; National Research Technological University “MISiS”

Email: bekarys@jinr.ru
Rússia, Dubna, 141980; Moscow, 119049

B. Yerzhanov

Joint Institute for Nuclear Research

Autor responsável pela correspondência
Email: bekarys@jinr.ru
Rússia, Dubna, 141980

Б. Мухаметулы

Joint Institute for Nuclear Research; Al-Farabi Kazakh National University; Institute of Nuclear Physics of the Ministry of Energy of the Republic of Kazakhstan

Email: bekarys@jinr.ru
Rússia, Dubna, 141980; Almaty, 050040 Kazakhstan; Almaty, 050032 Kazakhstan

N. Samoylova

Joint Institute for Nuclear Research

Email: bekarys@jinr.ru
Rússia, Dubna, 141980

V. Palacheva

Joint Institute for Nuclear Research; National Research Technological University “MISiS”

Email: bekarys@jinr.ru
Rússia, Dubna, 141980; Moscow, 119049

S. Sumnikov

Joint Institute for Nuclear Research; National Research Technological University “MISiS”

Email: bekarys@jinr.ru
Rússia, Dubna, 141980; Moscow, 119049

I. Golovin

Joint Institute for Nuclear Research; National Research Technological University “MISiS”

Email: bekarys@jinr.ru
Rússia, Dubna, 141980; Moscow, 119049

Bibliografia

  1. Summers E.M., Lograsso T.A., Wun-Fogle M.J. Magnetostriction of binary and ternary Fe–Ga alloys // Mater. Sci. 2007. V. 42. P. 9582–9594.
  2. He Y., Jiang C., Wu W., Wang B., Duan H., Wang H., Zhang T., Wang J., Liu J., Zhang Z., Stamenov P., Coey J.M.D., Xu H. Giant heterogeneous magnetostriction in Fe–Ga alloys: Effect of trace element doping // Acta Mater. 2016. V. 109. P. 177–186.
  3. Emdadi A., Palacheva V.V., Balagurov А.M., Bobrikov I.A., Cheverikin V.V., Cifre J., Golovin I.S. Tb-dependent phase transitions in Fe-Ga functional alloys // Intermetallics. 2018. V. 93. P. 55–62.
  4. Jin T., Wang H., Golovin I.S., Jiang C. Microstructure investigation on magnetostrictive Fe100-xGax and (Fe100-xGax)99.8Tb0.2 alloys for 19 ≤ x ≤ 29 // Intermetallics. 2019. V. 115. P. 106628.
  5. Wu Y., Chen Y., Meng Ch., Wang H., Ke X., Wang J., Liu J., Zhang T., Yu R., Coey J.M. D., Jiang C., Xu H. Multiscale influence of trace Tb addition on the magnetostriction and ductility of <100> oriented directionally solidified Fe–Ga crystals // Ph

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2. Fig. 1. Neutron diffraction spectrum of Fe81Ga19Er0.2 alloy measured on HRFD (high resolution) at room temperature. The calculated peak positions (strokes) and Miller indices are given for cell D03.

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3. Fig. 2. Profiles of the diffraction peak 400 of Fe81Ga19 alloy(Dy, Tb)0.1, measured on HRFD (high resolution) before (curve 1, diamonds) and after (curve 2, crosses) slow heating. Curve 3 (triangles) is the profile of the peak 300 (d = 1.386 Å) of the standard polycrystal La11B6. The peaks are normalized in amplitude and aligned in interplane distance.

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4. Fig. 3. Williamson–Hall construction for the widths of the fundamental diffraction peaks of Fe81Ga19(Dy, Tb)0.1 alloy in the states before heating (rhombuses) and after cooling (triangles). Miller indices of peaks are indicated. The numbers indicate the values of the microstresses of these two states. The dashed line is a contribution from the diffractometer resolution function. The dot errors are close to the size of the characters.

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5. Fig. 4. Neutron diffraction spectra of Fe81Ga19 alloy(Dy, Tb)0.1, measured on HRFD (average resolution) at room temperature before slow heating to 900 °C (a) and after cooling (b) to CT. The positions of the peaks of phases D03 and A1 (on the spectrum after cooling) are indicated.

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6. Fig. 5. Williamson–Hall construction for widths of superstructural diffraction peaks of Fe81Ga19(Dy, Tb)0.1 alloy in the state after heating–cooling. The calm line is a contribution from the resolution function of the diffractometer. Point errors are statistical.

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7. Fig. 6. Diffraction spectra of Fe81Ga19Dy01 alloy measured during its reheating to 900 °C (+2 °C/min) and subsequent cooling to CT (-2 °C/min). The axis of temperature is from bottom to top, the axis of interplanar distances is from left to right. The initial state of the alloy is phase A2, upon cooling, clusters of the ordered phase D03 were formed in the matrix of phase A2 and A1 is present in a small amount. Miller indices of peaks belonging to phases A2 and D03 are given for cell D03. The measurement time of one spectrum is 1 min, in total the 2D map contains about 900 spectra.

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8. Fig. 7. Dependence on the temperature of the diffuse background averaged over the interval d = (2.6–2.8) Å, measured during heating and cooling of the Fe81Ga19Dy0 alloy.1. The change in the slope of the dependence correlates with the formation of clusters of the ordered phase D03.

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9. Fig. 8. Temperature dependences of the intensities of the main (400) and superstructural (311) diffraction peaks of the D03 phase of Fe81Ga19Er0.2 alloy at its two heats (up to 900 °C) and cooling. The dependencies for the 1st and 2nd heats and the 2nd cooling (1st, 2nd) are shown. The dependencies for the 1st cooling are not shown, as they are almost identical to the 2nd cooling. The intensity scales for the main and superstructural peaks are different.

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10. Fig. 9. Temperature dependences of the intensities of the main (220) and superstructural (311) diffraction peaks of Fe81Ga19Dy0.1 alloy during its first (a) and second (b) heating and cooling. The intensity scales for the main and superstructural peaks are different.

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11. Fig. 10. Dependence on the temperature of the unit cell parameter (right scale) of Fe81Ga19 alloy during its heating and subsequent cooling and the intensities of the main (220) and superstructural (311) peaks (left scale) during cooling (transition A2 → A2 + D03). Inclined lines are a description of experimental points by a linear function in a certain temperature range. The figures indicate the temperature coefficient of linear expansion (in units of 10-5 1/K).

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12. Fig. 11. Temperature dependence of the intensity of the superstructural (311) peak (left scale) and its width (right scale) of the Fe81Ga19Er0.2 alloy during its second heating (a) and subsequent cooling (b). The variations indicated at the points are statistical. The lines are shown for clarity.

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13. Figure 12. Neutron diffraction spectrum of Fe81Ga19(Dy, Tb)0.1 alloy, measured in the region of large dhkl after cooling of the alloy. The scale along the ordinate axis has been increased. The main and superstructural peaks of phase D03 (111, 200, 220, 311) and peaks of phase A1 (111, 200) are present. There are no peaks of the m-D03 (110, 211) phase in the marked dhkl intervals.

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