Analysis of electrical resistivity at first-order transitions (L12 -> D019 -> B2) was for the first time conducted in the Fe-28.1%Ga alloy during heating, cooling, and at isothermal annealing. Phase transitions and alloy structure were additionally controlled in situ using neutron diffraction. The Avrami parameter for the reverse L12 <-> D019 transitions under isothermal conditions was calculated, with an analysis of the morphology of the growing phases conducted similarly to that of the L12 <-> D019 transition in the Fe-26.9Ga alloy from our previous study. The L12 + D019 phases coexistence interval in the Fe-28.1Ga alloy is determined to span 600-615 degrees C, and is in agreement with the phase diagrams proposed by Kubaschewski. The B2 -> D019 and D019 -> L12 transition kinetics vary greatly depending on instant cooling rates.

An analysis of the diffraction spectra of the Fe74Al26 alloy was conducted using a high-resolution neutron diffractometer to determine the size distribution of structurally ordered clusters dispersed within the structurally disordered matrix of the alloy. The Scherrer method was generalized for this purpose, based on the analysis of diffraction peak profiles, determining peak widths at heights of 1/5 and 4/5 of the maximum, and assuming the validity of the gamma distribution for cluster sizes (Pielaszek method). A comparison of results obtained using the Scherrer, Williamson–Hall, and Pielaszek methods was carried out, demonstrating good agreement between them. An algorithm for calculating the log-normal distribution function of cluster/particle sizes is proposed. The experimental data were obtained using a time-of-flight neutron diffractometer, and the analysis was performed for two variants of variable scanning: in crystallographic (direct) (d-scale) and reciprocal (H-scale) spaces, with estimates of possible systematic errors. It was concluded that the determined average sizes possess the necessary degree of stability, meaning they weakly depend on the applied variable scanning and the total number of experimental data points.

Analysis of the first-order transition between D03 and two close-packed phases (L12, D019) in Fe3Ga-type alloy (26.9 %Ga), is carried out at different cooling rates from the range of equilibrium D019 phase and at different cooling rates from the range of equilibrium A2 phase. The structure was controlled by neutron diffraction, SEMEBSD and additionally characterized using VSM and ATP tests. The obtained results clarify kinetics of D019 phase growth and transition to low temperature equilibrium L12 phase. We demonstrated that D019 phase is ferromagnetic at room temperature with very low saturation magnetostriction.

The evolution of the structural phases of the Fe-42.4 at% Ga alloy was studied using neutron diffraction performed with high-intensity continuous scanning in a wide temperature range. The sequence of occurrence of structural states both during heating and subsequent cooling is reported. The structural phases Fe13Ga13, Fe13Ga9, alpha-Fe6Ga5, D03, L12, A2 are present in the alloy and they disappear upon heating above 800 degrees C into the partially ordered B2/A2 phase. The high-temperature Fe13Ga13 intermetallic compound exists in two temperature ranges: 25-580 degrees & Scy; and 770-800 degrees & Scy; during heating and precipitates again during cooling. The persistence of the phase upon cooling down to room temperature is inconsistent with the phase diagram, indicating that the alloy remains in a metastable state after the heating and subsequent cooling. The D03, alpha-Fe6Ga5 and L12 phases are formed during cooling.

To determine the size distribution of structurally ordered clusters dispersed within a structurally disordered alloy matrix, we analyze the diffraction patterns of the Fe74Al26 alloy obtained using a high-resolution neutron diffractometer. This analysis employs the generalized Scherrer method, which involves analyzing diffraction-peak profiles, determining peak widths at heights of 1/5 and 4/5 of the maximum, and assuming a gamma distribution for cluster sizes (Pielaszek method). We compare the results obtained using the Scherrer, Williamson–Hall, and Pielaszek methods, finding them to agree. We propose an algorithm to calculate the log-normal distribution function of cluster/particle sizes. Experimental data are obtained using a time-of-flight neutron diffractometer. The analysis is conducted for two scanning variable options: in the crystallographic (direct) (d scale) and reciprocal (H scale) spaces, and possible systematic errors are evaluated. We conclude that the average sizes determined in this manner possess the necessary degree of stability, showing a weak dependence on the applied scanning variable and the total number of experimental points.

Anelastic relaxation in the temperature range from 0 to 300°C (0.1-30Hz) in ternary Fe-26(Al+Ga)-0.1Tb alloys is experimentally studied and analysed with respect to binary Fe3Al and Fe3Ga intermetallic compounds. The Snoek-type relaxation due to cyclic stress-induced carbon atom jumps between octahedral interstices in the α-Fe based solid solution (Fe-C-Al,Ga) is recorded and analysed. The Snoek-type effect in the ternary Fe-26(Al+Ga)-0.1Tb alloys has a higher activation energy (up to ∼1.2eV) in comparison to α-Fe-C (0.83eV). The relaxation effect demonstrated significant broadening with respect to Debye peak with a single relaxation time and splitting into two separated peaks at a certain ratio Al/Ga. Snoek-type effect provides a unique opportunity to measure C atom diffusivity at relatively low temperatures. Influence of the chemical composition and the measuring frequency on the activation parameters in Fe-26(Al+Ga)-0.1Tb alloys are reported and analysed to estimate the impact of Al and Ga atoms on C atom diffusivity in α-Fe based solid solution.

The formation of nanoprecipitates in the Fe81Ga19 alloy doped with Tb (similar to 0.1 at. %) was studied by small-angle neutron scattering (SANS). Measurements at room temperature for several samples pre-aged at a fixed temperature in the range of (300-700)degrees C revealed a dilute system of precipitates with a characteristic size at nanoscale (<1000 & Aring;) growing with an increase in ageing temperature. In situ measurements during isothermal ageing at 300 degrees C for 3 h revealed fast (order of 10 min) formation of precipitates. SANS analysis is consistent with the results of neutron diffraction experiments, which suggest the microstructure of this alloy as a matrix of disordered atomic structure (A2 phase) with embedded precipitates of the structurally and magnetically ordered D0(3) phase.

An analysis of the first order transition kinetics between D03 and L12 phases in Fe3Ga-type alloy is carried out. Structure and magnetostriction of the samples were carefully controlled by SEM-EBSD analysis and magnetostriction tests after different heat treatments, and additionally in in situ regime by VSM and DSC. C-shaped curves for time-temperature-transition (TTT) diagram based on the results of the EBSD analysis of Fe-27Ga alloy are constructed in the temperature range between 400 and 550 degrees C. TTT diagram shows that the nucleation rate for L12 phase increases in the sequence 400 -> 475 -> 550 degrees C, while the growth rate reaches a maximum at about 500-525 degrees C. Effect of D03 <-> L12 thermocycling on the kinetic of the D03 -> L12 transition is studied for the first time. The amount of the L12 phase after sample re-quenching and subsequent annealing at the same annealing temperature and time, significantly increases compared with the first cycle quenching and subsequent annealing, demonstrating memory effect of previous transitions.

The high-resolution Fourier diffractometer (HRFD) has been in routine operation since 1994 at the long-pulse neutron source, the IBR-2 reactor, in Dubna. Its fast Fourier chopper provides probably the best compromise between very high resolution in reciprocal space (Δd/d ≈ 0.001) and the intensity. For further improving intensity of TOF-diffraction pattern, a wide-aperture ring backscattering detector (BSD) has been developed on the basis of ZnS(Ag)/6LiF scintillator. BSD is designed in the form of 6 concentric rings, each of which is subdivided into 12 identical parts. The main parameters of the detector are the following: range of scattering angles is 2θ = (133 - 175) degrees, covered solid angle is Ωd ≈ 2.0 sr, average percentage absorption efficiency gets closer to 85%, geometrical contribution to resolution function does not exceed Δd/d = 0.0005. In the report the concept of the detector is described and its data acquisition system is presented. The start of operation of the detector at the HRFD is scheduled for 2024.

Currently, the dominant model for the formation of enhanced magnetostriction of Fe-Ga alloys is based on the assumption of the presence of microscopic inclusions with a tetragonal L60 structure in the cubic matrix of the alloy. However, no evidence for the presence of this phase in the bulk of the alloys in amounts sufficient to have a noticeable effect on the magnitude of magnetostriction has been obtained so far. To test this hypothesis, a detailed scanning of the reciprocal space of Fe81Ga19Tb0.1 and Fe73Ga27 single crystals was carried out at ESRF at high photon flux stations. In particular, it was possible to reliably record superstructure diffraction peaks, the intensity of which was at a level of 2 x 10-6 from the intensity of the fundamental peaks. Nevertheless, neither the presence of superstructure diffraction peaks obviously belonging to the L60 phase nor the tetragonal splitting of the fundamental diffraction peaks into components, which could indicate the presence of this phase in the samples, was detected. Similar results were obtained using complementary methods (electron and neutron diffraction). Based on the performed analysis of the background level in the places of the expected positions of superstructure peaks of the L60 phase, it was found that the volume fraction of this phase in the Fe81Ga19Tb0.1 alloy cannot exceed 0.2%. The presence of a previously discovered X phase with hexagonal or orthorhombic symmetry in a crystal with 27 at. % Ga was confirmed.

New data on phase states and structural phase transitions in alloys Fe73Ga27 doped with Dy, Er, Tb, and Yb in an amount of about 0.5 at

The results of high-precision electro-resistivity measurements, rho(T), for Fe-18.5%Ga alloy over a wide temperature range are presented. An anomaly in the rho(T) temperature behavior is detected and it is proved that it correlates well with the change in the unit cell lattice parameter of the alloy and with the results obtained from measuring magnetization, dilatometry and positron annihilation. From the neutron diffraction data, it follows that the detected anomaly is associated with the formation of a cluster-like microstructure of the alloy: in the structurally disordered A2 matrix, regions with partially ordered D03 phase are formed. Interpretation of this non-monotonic behaviour of rho(T) is discussed.

Phase transitions between structurally ordered phases in Fe-Ga alloys have been studied upon their heating to 850 C and subsequent cooling to room temperature by neutron diffraction in real-time mode. The transitions between four types of phases have been analyzed: D03 -> L12 (both cubic phases), L12 F iota D019 (cubic - hexagonal), D019 F iota A2 (hexagonal - cubic). It has been established that all phase transitions include stage of the formation of a disordered state and have a combined, diffusive-displacive nature. The diffusion stages are necessary for the disordering and ordering of the structure, the displacive stage provides a change in the type of the crystal lattice. It can be concluded that the formation of an intermediate disordered state followed by a transition to the final equilibrium state is less energy-consuming than the direct transition to the final state. During the observed transformations, no traces of predicted intermediate structurally ordered tetragonal phases were found. These results may provide new insight into the microscopic basis for the formation of enhanced magnetostriction in Fe-Ga alloys.

Abstract—New data on the phase compositions and structural transformations in a number of Fe81Ga19 alloys doped with trace amounts (≤0.2 at

Analysis of the first-order transition between D03 and two close-packed phases (L12, D019) in Fe3Ga-type alloy (26.9%Ga), is carried out at different cooling rates from the range of equilibrium D019 phase and at different cooling rates from the range of equilibrium A2 phase. The structure was controlled by neutron diffraction, SEM-EBSD and additionally characterized using VSM and ATP tests. The obtained results clarify kinetics of D019 phase growth and transition to low temperature equilibrium L12 phase. We demonstrated that D019 phase is ferromagnetic at room temperature with very low saturation magnetostriction.

Anelastic relaxation at elevated temperatures (300-600 degrees C) in binary and ternary Fe-20(Al+Ga) alloys is experimentally studied and analyzed. Two transient effects due to the irreversible annihilation of quenched vacancies and reversible order (short range D03 & LRARR; disorder A2) transition overlap with thermally activated Zener relaxation due to reorientation of substitution atoms under the stress applied. 'Map' of these effects at heating and cooling for sub-resonance Hertz-range frequencies is built to demonstrate similarities between binary Fe-Al, Fe-Ga, and ternary Fe-Al-Ga alloys. Influence of chemical composition and measuring frequency on these effects and their combination is analyzed. Zener relaxation in the ternary alloy is discussed in terms of contribution from Al-Al, Ga-Ga, and Al-Ga atom pairs.

In situ neutron diffraction and internal friction were combined for the comparative analysis of structural and functional properties of Fe-26Al alloy. Three different alloy states were studied: after rapid solidifica-tion in graphite mold, after annealing at 900 degrees C (0.5 h) and water quenching, after annealing at 450 degrees C (24 h) and slow cooling. Structural phase states and microstructure types were determined. The obtained results make it possible establishing the relationship between the thermal treatments, microstructure, phase transformations on the one hand and anelastic (internal friction) properties on the other.(c) 2022 Elsevier B.V. All rights reserved.

A detailed neutron diffraction study of a stoichiometric Fe3Ge alloy with different initial states in a wide temperature range (up to 1000 K) made it possible to accurately reveal the features of magnetic and structural phase transformations in it. The use of complementary x-ray diffraction and analysis of neutron diffraction patterns by the Rietveld method allowed reliably separating the nuclear and magnetic contributions to the intensity of the diffraction peaks and performing refinement of the Fe3Ge magnetic state characteristics. Both main phases appearing in Fe3Ge are ferromagnetic with T-C = 629 K (hexagonal, D0(19)) and T-C = 714 K (cubic, L-12). In D0(19), the presence of a spin-flip transition (T-sf = 385 K) was confirmed and the temperature dependence of the components of magnetic moment along the hexagonal axis and in the basal plane was obtained. It was shown that the transformation between ordered L1(2) and D0(19) structural states, predicted by the equilibrium-phase diagram, includes three steps: two diffusional stages (L1(2) -> A1, A3 -> D0(19)) and one displacive stage (A1 -> A3). The obtained structural data suggest that in Fe-Ge, as well as in Fe-Ga alloy, direct transitions between ordered phases are impossible. They should include a transition between disordered states.

The evolution in phase composition of as-cast Fe-(31-35) at% Ga alloys during continuous heating up to 850 degrees C with subsequent cooling was studied. Based on the results obtained by neutron diffraction, con-clusions were drawn about clearly distinguishable stages of phase formation during heating and cooling of metastable high-gallium alloys. Upon heating, the phase composition of studied alloys was found to change in a similar way, namely: BCC + Fe13Ga9 (absent in Fe-31.1 at% Ga) -> BCC+ Fe13Ga9 + L12 -> BCC + L12 + alpha- Fe6Ga5 -> B2 + alpha-Fe6Ga5 -> B2. Upon cooling, the following sequence of phase states was realized in Fe-32.9Ga and Fe-34.4 at% Ga alloys: B2 -> B2 + alpha-Fe6Ga5 -> D03 + L12 + alpha-Fe6Ga5. Fe-31.1 at% Ga alloy was found to be characterized by the sequence: B2 -> B2 + L12 -> D03 + L12 + Fe13Ga9. (c) 2022 Elsevier B.V. All rights reserved.

We report on experimental investigations of a Ni2.36Mn0.64Ga Heusler alloy, which transforms to tetragonal martensite at cooling below Ms ≈ 271°С. The evolution of lattice constants was tracked by in situ neutron diffraction measurements. It was found that the martensite tetragonality c/a gradually decreases during heating from room temperature to austenite transition start temperature As ≈ 272°С. The phenomenon of martensite stabilization was investigated by differential scanning calorimetry utilizing three different protocols of the martensite aging. It was found that the martensite aging at a constant temperature T = 255°С merely shifts the reverse transformation to higher temperatures, while the reverse transformation temperature interval (Af – As) remains the same (≈ 30°C) independently of aging time. On the other hand, a multistep aging at different temperatures starting from T = 255°С not only shifts the reverse transformation temperature, but makes the transformation temperature interval narrower down to As – Af ≈ 10°C.