Phase transitions in Fe-27Ga alloys: Guidance to develop functionality

Temperature evolution of Fe–27Ga structure: comparison of in situ X-ray and neutron diffraction studies

“…The phase-transition temperatures obtained in the XRD experiment coincide with the XRD results for previous experiments on samples with the same composition (Golovin et al, 2015), where the D0 3 ! L1 2 transition is detected between 412 and 425 C. The neutron data on phase-transition temperatures are in good agreement (within 5 ) with previous neutron studies of alloys with similar compositions (Golovin et al, 2018;Balagurov et al, 2017). Such shifts to lower temperature values in XRD experiments, as well as the sharp rise in peak intensities of the new phases observed in XRD data compared with ND data (at the same temperature-change rate), may indicate that, in general, a new Fe-Ga phase rises from the surface area deep in the sample.…”

“…XRD phase analysis shows that after such cleaning the top side is still characterized by an A2 phase. The absolute values of unit-cell parameters obtained from XRD and ND data at room temperature after cooling and heating [a = 2.90203 (4) Å for A2 phase and a = 2.9219 (4) Å for D0 3 phase] are in good agreement with the rising tendency of the unit-cell parameter with increasing Ga content (Golovin et al, 2019).…”

Anelastic Effects in Fe–Ga and Fe–Ga-Based Alloys: A Review

“…Activation parameters (τ 06 ≈ 2 × 10 −16 s and H 6 = 2.7 eV) suggest a grain boundary mechanism of this peak. Later, a similar peak was reported for Fe–27Ga (2.8 eV) [ 46 , 47 ], and, most recently, the interpretation of this effect as a grain boundary peak was confirmed for Fe–30Ga alloy with activation parameters: τ 0 ≈ 10 −12 s and H ≈ 2.1 eV [ 61 ].…”

“…Our experimental results do not support effectiveness of this method, and we believe that even though this approach helps to increase non-magnetic contribution to damping, it significantly decreases magneto-mechanical component of damping. It is also important to remember that D0 3 and L1 2 phases have opposite signs of magnetostriction; as a result, their saturation magnetostriction decreases and may even be equal to zero [ 46 , 131 , 132 ], which according to the Smith and Birchak approach, leads also to zero magnetomechanical damping. Indeed, most recently published results by another group [ 63 ] clearly confirm that two-phase D0 3 + L1 2 Fe–27Ga alloy may have different damping mechanisms at lower and higher strain amplitude: D0 3 phase with higher magnetic damping than non-magnetic damping plays a dominant role under a lower strain amplitude, while L1 2 phase with higher non-magnetic damping than magnetic damping plays the main role under a higher strain amplitude.…”

“…Our studies of thermally activated (Snoek and Zener relaxations), transient (due to A2 ↔ D0 3 , D0 3 → L1 2 , L1 2 → D0 19 , D0 19 → B2 phase transitions), and amplitude-dependent (damping) effects in Fe–Ga alloys were strengthened by cooperation with colleagues from China, Spain, Switzerland, Taiwan, and the US. Studies of phase transitions were supported by parallel real-time neutron diffraction measurements at JINR, Dubna [ 24 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ]. A review of frequency- and temperature-dependent anelastic effects in Fe–Ga alloys was presented by the author of this paper at the 18th International Conference on Internal Friction and Mechanical Spectroscopy (ICIFMS-18, Brazil, 2018).…”