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Effect of La addition on high-temperature order-disorder phase transformation in Fe − 18Ga alloy
Intermetallics 111 (2019) 106496
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Effect of La addition on high-temperature order-disorder phase transformation in Fe − 18Ga alloy
T
Meng Suna,b, Yinxing Wua,b, Weibin Jianga, Wang Liua, Xianping Wanga,∗, Yunxia Gaoa, Rui Liua, Ting Haoa, Wen Wenc,∗∗, Qianfeng Fanga a
Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei, 230031, PR China Department of Materials Science and Engineering, University of Science and Technology of China, Hefei, 230026, PR China c Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai, 201204, PR China b
ARTICLE INFO
ABSTRACT
Keywords: Internal friction Order-disorder LaGa2 Zener relaxation Hardness
The microstructure, internal friction (IF) behavior spectra, heat flow curves, and mechanical strength of Fe18Ga-xLa (x = 0.05, 0.1, 0.2, 0.5, and 1.0 at.%) alloys were systematically analyzed in this investigation. In the IF spectra, a relaxation IF peak (Labeled as P1) and a peak related to order-disorder phase transition (Labeled as Ptr) are observed in the temperature range of 400 °C–690 °C. It is found trace La doping has a significant effect on the Ptr peak. With the increase of the La-doped content, the peak of Ptr gradually shifts to a lower temperature and the net peak height decreases. Combining with phase diagram, DSC, Grazing Incidence X-ray diffraction (GIXRD) spectra and SEM, the mechanisms of the reduction of both the critical temperature and the strength of Ptr peak for the Fe-18Ga-xLa alloy are ascribed to the precipitation of LaGa2 phase, which reduces the Ga content gradually in the matrix. Further, the mechanism is verified in Fe-18.1Ga alloy and Fe-19.3Ga alloy. In addition, the trace La doping can significantly improve the mechanical strength of the Fe − 18Ga alloy.
1. Introduction The addition of non-magnetic Ga element to the body-centered cubic (b.c.c) α-Fe is known to yield extremely large magnetostrictive coefficient along [100] direction of λ100 > 260 ppm, with maxima occurring at 17–19 and 27 at.% Ga [1–3]. Recently, the unique magnetostrictive property of Fe − 18Ga alloy is mainly considered to originate from the nanosized tetragonal phase (L16 or L10), a phase of lower symmetry, which associated with order–disorder transition of Ga atoms in the matrix [4,5]. However, it is much difficult to distinguish this structure with the usual characterization methods, such as, X-ray diffraction (XRD), Scanning electron microscope (SEM), and Transmission electron microscopy (TEM), due to the little content and instability [6–8]. Therefore, the accurate and in situ characterization of order-disorder transition of Ga atoms in the matrix for Fe − 18Ga binary alloy is required to help us understand and tune mechanical properties and magnetostriction, which is beneficial for applications of microdisplacement control, energy-harvesters and spintronic devices [9]. IF behavior is particularly sensitive to the phase transition process and internal defects of solid materials. In the last few years, rich IF ∗
phenomena of Fe-Ga-based alloys were discovered due to phase structures, Ga–Ga atom pairs, and phase transitions [10–13]. M. Ishimoto et al. firstly studied the effect of temperature on the IF behaviors of Fe17 at.% Ga alloy, and found there was a high-damping plateau (up to 10−2) over the temperature range of -190-300 °C, which was ascribed to magnetoelastic hysteresis originating from the large magnetostriction [14]. Next, Golovin's group had done a lot of work on the mechanical spectra for Fe-(17–19) at.% Ga based alloy combined with neutron diffraction. Besides the high damping plateau below 300 °C, a phase transition IF peak near 450 °C caused by ordered b.c.c D03 (Fe3Ga, sp. gr. Fm3m) to face-centered cubic (f.c.c) L12 (Fe3Ga, sp. gr. Pm3 m) transition, a relaxational-type IF peak near 500 °C, and a weak frequency independent IF peak near 490 °C were also observed [15–18]. It worth noting that A.E. Boyer et al. proved that the relaxationaltype IF peak belongs to Zener peak rather than grain boundary relaxation peak through the Fe-17.4 at.% Ga single crystal IF experiment, and found that the relaxation magnitude for Fe–Ga binary alloy was proportional to concentration of Ga atoms up to 19 at.%, and then was followed by a pronounced decrease for the alloys with > 20 at.% Ga due to D03 and L12 ordering of Ga atoms in Fe–Ga alloys [17,19]. Besides the Zener relaxation peak, the frequency independent IF peaks
Corresponding author. Corresponding author. E-mail addresses: [email protected] (X. Wang), [email protected] (W. Wen).
∗∗
https://doi.org/10.1016/j.intermet.2019.106496 Received 8 April 2019; Received in revised form 29 April 2019; Accepted 4 May 2019 Available online 14 May 2019 0966-9795/ © 2019 Elsevier Ltd. All rights reserved.
Intermetallics 111 (2019) 106496
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Fig. 1. (a) IF (T =2 K/min, f = 1 Hz, and ε = 3 × 10−5) versus temperature for the as-cast Fe − 18Ga alloy and the Fe-18Ga-0.1La alloy annealed at 900 °C in hydrogen atmosphere, respectively; (b) IF-behaviors of P1 and Ptr peaks after deducting the backgrounds. M. Sun et al..
(Ptr) near 575 °C were observed in our group, which is also particularly sensitive to D03 ordering of Ga atoms in the matrix [20,21]. And it is interesting that quenching from the temperature range of Ptr peaks can improve the magnetostriction of Fe − 18Ga based alloys significantly [20,22]. Therefore, a detailed study of the high-temperature ordering behaviors of Fe − 18Ga based alloys is helpful to design precise heattreatment methods to obtain high functional properties. In recent years, trace rare earth dopants was found can induce giant magnetostriction in Fe–Ga binary alloys [8,23,24]. Especially, 0.2 at.% La doping can produces the largest magnetostriction of up to ∼600 ppm, which was suggested to arise mainly from tetragonal distortion of lower symmetry nano-heterogeneities with fixed Ga–Ga pairs [24]. In this paper, The high-temperature order-disorder phase transition of Fe − 18Ga alloys doped by different La contents were carefully studied by IF spectra and heat flow curves. We found that with the increase of the La content, the critical temperature of high temperature order-disorder phase transition decreases gradually. Combined with phase diagram, GI-XRD spectra, and SEM, it was found that the mechanism of the reduction of the phase transition temperature induced by La doping was ascribed to the precipitation of LaGa2 phase, which reduced the Ga content gradually in the matrix. Furthermore, in order to verify the mechanism of the temperature reduction of the orderdisorder phase transition for Fe − 18Ga alloys doped by La, the IF spectra of Fe-18.1Ga and Fe-19.3Ga binary alloys were studied in detail. In addition, the mechanical strength of Fe-18Ga-xLa was also investigated. The obtained results will contribute to deepen the understanding of D03→A2 order-disorder phase transition in the Fe–Ga based alloys and provide references for the precise design of the preparation process of the Fe–Ga based alloy with high functional properties.
beamline BL14B1 can be found in Refs. [25,26]. The IF behaviors of samples were measured by a computer-controlled automatic inverted torsion pendulum with the force-vibration mode, in which different frequencies (0.2∼5 Hz) were carried out in one measurement run with a heating rate of 2 K/min over a temperature range from RT to 800 °C, then held for 10 min, and finally cooled at a speed of 2 K/min. The sample size in the IF measurement is about 2 × 1 × 23 mm3. The maximum torsion strain amplitude was kept at 3 × 10−5 in all measurements. The whole measuring process was carried out in vacuum (∼10Pa) to avoid oxidation at high temperature. Besides IF tests, differential scanning calorimetry curves (DSC, PerkinElmer, USA) were also carried out to measure the order-disorder phase transition temperatures at a heating/cooling rate of 10 K/min. All hardness tests were performed on the surfaces of Fe-18Ga-xLa samples using a Nano-Indenter G200 mechanical testing device (Agilent) with a displacement resolution of 0.01 nm/s and a strain rate of 0.05 s−1. Average hardness values were calculated from 12 to 17 separate indents, which obtained for contact depths between 1000 nm and 1500 nm, corresponding to a steady-state hardness value. All samples with the size of 10 × 10 × 2 mm3 were mechanically polished before testing to ensure the data stability. 3. Results 3.1. Descriptions of P1 and Ptr peaks Fig. 1a shows the IF-temperature spectra of as-cast Fe − 18Ga and Fe-18Ga-0.1La alloys, respectively. A high damping plateau is observed over the temperature range of RT to 230 °C, and then the IF value decreases rapidly to about 0.003. Besides the high damping plateau, there are two pronounced IF peaks (labeled as P1 at a lower temperature range and Ptr at a higher temperature range) over the temperature range from 300 to 700 °C. It should be noted that the as-cast Fe − 18Ga specimen was wire-cut from a large sample weighing 25 kg by arc melting, while the La-doped sample is wire-cut from a small sample weighing 50 g. Thus, the cooling rate of the small sample after melting is much higher than that of the as-cast Fe − 18Ga alloy, which causes the Ptr peak of the Fe − 18Ga specimen doped by La annealed in hydrogen to be lower than that of the as-cast Fe − 18Ga specimen. Blue and pink dashed lines are IF backgrounds (BGs) for the as-cast Fe − 18Ga alloy and the Fe-18Ga-0.1La alloy, respectively. It is known that an IF background (Qb 1), as a function of temperature (T), can be expressed as [27].
2. Experimental technique The ingots with nominal atomic composition Fe-18Ga-xLa (x = 0.05, 0.1, 0.2, 0.5, and 1.0 at.%) were produced in a vacuum arc melting furnace using pure Fe (99.99 wt%), pure Ga (99.99 wt%) and La (99.9 wt%) under Ar atmosphere. For comparative study, Fe-18.1Ga and Fe-19.3Ga binary alloys were also prepared. All compositions in this paper are indicated in atomic per cent. In order to prevent the burning loss during the smelting process, Ga and La elements have been weighed for 2% excess, and the mater ingots were melted for four times to ensure compositional homogeneity. In addition, all the samples were annealed at 900 °C for 2 h in hydrogen atmosphere before testing, and the cooling rate was 5 K/min. The microstructures were studied by Grazing Incidence X-ray diffraction (GI-XRD) spectra. The X-ray diffraction data were obtained at beamline BL14B1 of the Shanghai Synchrotron Radiation Facility (SSRF) with a wavelength of 0.6887 Å. The detailed information about
Qb 1 = A + Bexp ( C / kT ),
(1)
where A, B and C are constants and k is the Boltzmann constant. After the BG was subtracted from the curves, the IF-behaviors of P1 and Ptr 2
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peaks are shown in Fig. 1b. P1 peak: The establishment of the formation mechanism for P1 peak experienced a tortuous process. In Fe − 13Ga alloy, Golovin et al. first observed that P1 peak was located near 500 °C and the mechanism was suggested to originate from grain boundary relaxation, while Zener peak was suggested to be located at a lower temperature, and the peak was a process IF peak: the peak appeared during the heating process and disappeared during the cooling process. It was considered that the ordering of Ga atoms in the matrix during the cooling process led to the disappearance of Zener peak [10]. With the further study of the IF spectra of Fe − 13Ga specimens, different heat-treatment conditions also had a weak influence on the P1 peak. Therefore, it was suggested that the peak was originated from Zener relaxation, while the activation energy of the process peak was only 0.85 eV and disappeared after annealed at 350 °C. Thus, the mechanism of the process peak was suggested to be dislocation movement, and the relaxation peak caused by the grain boundary was pushed toward the IF peak at a higher temperature [28]. Fang et al. conducted a preliminary study on the IFtemperature spectrum of Fe(Fe80Ga20)99.95(NbC)0.05 alloy. It was also considered that the P1 peak was Zener peak, and the higher temperature peak was suggested as the grain boundary peak based on activation energy [29]. However, the grain boundary peak at a high temperature was not observed in the Fe − 17Ga alloy, and thus the process peak was again recognized as the Zener peak, and the P1 peak was regarded as the grain boundary peak [11]. Further in the study of Fe-18(Ga + Al) alloys, the mechanism of the P1 peak was re-identified as a result of Zener or grain boundary relaxation [15]. Since the P1 peak was not clearly observed in both Fe − 3Ga and Fe − 27Ga, the mechanism of the P1 peak tends to be the Zener relaxation [30]. Further, through the IF experiments for the Fe-17.4Ga single crystal and the Fe–Ga polycrystalline samples with 8–33 at.% Ga, it was found that the P1 peak was still present in the IF spectrum of Fe-17.4Ga single crystal. With the increase of Ga content, the relaxation magnitude gradually increases. After the Ga content reaches 17–19 at.%, the relaxation magnitude decreases rapidly, and disappears when the Ga content reaches to 23–25 at.% [17,19]. These phenomena basically confirm that the mechanism of P1 peak is Zener relaxation. Ptr peak: It can be seen that the IF spectrum for the Fe − 18Ga alloy has a broad IF peak as shown in Fig. 1b, which can be divided into two subpeaks: Ptr1 at a lower temperature and Ptr2 at a higher temperature. In previous studies, we suggested that the formation mechanisms of these two IF peaks originated from D03→(B2) and (B2)→A2, respectively [20]. In the IF spectrum of the Fe − 18Ga specimen doped by La, the Ptr peak for the Fe − 18Ga specimen doped by La is asymmetric after deducting the high temperature IF background. Thus, besides the significant Ptr1 peak, the Ptr2 peak also exists. However, it is difficult to determine the specific transition point of the (B2)→A2 phase transition due to the difficulty of the fitting of the composite Ptr peak, and in this paper, we will discuss the whole Ptr peak caused by order-disorder phase transition D03→(B2)/A2 instead of discussing the Ptr1 and the Ptr2 peak separately. From Fig. 1b, it can be seen that the Ptr peak position shift to a lower temperature when Fe − 18Ga alloy is doped with 0.1 at.% La, which indicates that trace La doping has a significant effect on the Ptr peak position.
peak position of P1 does not change significantly, but the peak position of Ptr decreased gradually from 571 °C to 504 °C. It is noteworthy that the peak strengths of P1 and Ptr seem to increase with the increase of La content, but this phenomenon is not real because the two peaks interfere with each other as the Ptr peak approaches the P1 peak. As for the high damping plateau that mainly originated from magneto-mechanical hysteresis [11], the increase in the La-doped content does not significantly enhance the damping capacity (f = 3 Hz, ε = 3 × 10−5) of Fe-18Ga-xLa alloys, or even there is a slight decrease. P1 peak is attribute to Zener relaxation as described in Ref. [17], and the effects of trace La doping on the peak strength and position are not obvious. The Ptr peak is a frequency-independent IF peak that exhibiting a typical characteristic of a phase transition. Herein, the mechanism of the Ptr peak is suggested to the D03→(B2)/A2 phase transition, because the IF peak induced by (B2)→A2 phase transition is difficult to separate from the whole Ptr peak. As the La content increases, the Ptr peak gradually shifts to a lower temperature, indicating the doping of La will have a significant effect on the order-disorder phase transition. The corresponding mechanism will be further discussed combined with Grazing Incidence X-ray diffraction (GI-XRD) results in the following sections. Fig. 3a shows an example of P1 peak fitting and the estimation method of the net Ptr peak height ( Q Ptr1) for the Fe-18Ga-0.05La sample measured at 1 and 3 Hz, respectively. The IF curve with relaxation mechanism can be well fitted by one or more Debye peaks and background based on a non-liner fitting method [31]. Thus the peak temperature at different measurement frequencies can be precisely determined. For the Debye peak, it can be expressed by the equation for IF [32]
Q
1
=
1+
2 2
=
e
x
1 , + ex
(2)
where Δ is the relaxation strength, is the relaxation time, w is the circular frequency (=2πf, f is the measuring frequency), and x = In ( ). The can be expressed as
=
0 exp(H / kT ),
(3)
where 0 is the pre-exponential factor, H is the activation energy, k is Boltzmann constant, and T is the absolute temperature. Thus, the = 1, and Debye peak is maximum of Debye peak occurs when symmetrical in 1/T scale. With the net peak temperatures at different frequencies, the apparent activation enthalpy H can be evaluated accurately. Fig. 3b shows the Arrhenius plots (natural logarithm of circular frequency ω versus the reciprocal of net peak temperature 1/TP ) for the Fe-18Ga-0.05La sample. The relaxation activation energy H is determined as (3.0 ± 0.2) eV, which is close to the reported results of Zener relaxation in Fe-Ga-Al or Fe–Cr system [15,33]. The relaxation parameters of P1 peaks, the peak positions and the net peak heights of Ptr peaks for Fe-18Ga-xLa (x = 0.05, 0.1, 0.2, 0.5, and 1.0 at. %) samples are shown in Table 1. There are three points worthy of attention: Firstly, with the increase of La content, the activation energy and peak position of P1 IF peak basically remains unchanged. Next, with the increase of Ga content, the IF peak temperature of Ptr peak shifts to a lower temperature regardless of the heating or cooling process. Finally, the peak strength of Ptr peak decreases gradually with the increase of La-doped content during the heating process.
3.2. IF-temperature spectra Fig. 2a–e shows the variations of IF versus temperature for Fe-18GaxLa (x = 0.05, 0.1, 0.2, 0.5, and 1.0 at.%) samples at five different vibration frequencies, the heating rate and the test amplitude were maintained at 2 K/min, 3 × 10−5, respectively. It can be seen from Fig. 2a–e that a high damping plateau with IF value of 0.01 is observed over the temperature range of RT to 230 °C, and then the IF value decreases rapidly to about 0.003. Besides the high damping plateau, the Ptr peak shows obvious asymmetry, suggesting that it is a compound IF peak. With the increase of La content from 0.05 at.% to 1.0 at.%, the
3.3. Heat-flow curves Fig. 4a shows the heat flow curves for Fe-18Ga-xLa samples. An obvious step at around 500 °C and a sharp endothermic peak around 690 °C were observed. The former corresponds well to the Ptr peak related to order-disorder phase transition, and the latter corresponds to the ferro-paramagnetic transition temperature (Tc). With the increase of La-doped content, it can be seen that the step temperature related to 3
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Fig. 2. (a–e) Temperature dependence of the IF (Q−1) for continuous heating for Fe-18Ga-xLa (x = 0.05, 0.1, 0.2, 0.5, and 1.0 at.%, respectively.) samples at five different frequencies of 0.2, 0.5, 1, 3, and 5 Hz. M. Sun et al..
the Ptr peak decreases gradually, while Curie temperature point tends to move slightly to a higher temperature. Fig. 4b shows the variation of order-disorder phase transition point with La-doped content during heating and cooling processes. It can be clearly seen that DSC data are in good agreement with the IF results, and there are obvious thermal hysteresis with the temperature difference of about 40 °C.
on the surface of the material, so it should not be used as a criterion for the precipitation of the second phase. In order to further explore the phase structure distribution in the material, the high-resolution amplification curves of GI-XRD spectra between 10 and 30° are given in Fig. 5b. Compared with the standard diffraction peaks, LaGa2 structure phase is observed in all Fe-18Ga-xLa samples besides A2 and D03 phases. For the Fe-18Ga-xLa alloys, as the La-doped content increases, more LaGa2 structural phases are formed gradually, resulting in a decrease in Ga content in the matrix. On the one hand, the decrease in Ga content will lower the critical temperature of D03→A2 order-disorder phase transition according to the metastable phase diagram [34]. On the other hand, according to the lever principle, after the same preparation process and heat treatment, the decrease of Ga content in the matrix leads to a decrease in the relative content of D03 at room temperature.
4. Discussion Fig. 5a shows the GI-XRD profiles for Fe-18Ga-xLa (x = 0.05, 0.2, and 1.0 at.%, respectively) samples. The basic diffraction peaks are (110), (200), and (211), respectively, and all samples exhibit the similar cubic structure as α-Fe. Since GI-XRD spectrum is especially sensitive to the microstructure and stress distribution in the alloy, and the peak splitting observed at the high angle (211) is mainly caused by the stress
Fig. 3. (a) Temperature dependence of IF (Q−1) for an Fe-18Ga-0.05La sample measured at 1 and 3 Hz, respectively. The symbols are experimental data points and solid lines are the total fitting curves. The dotted line and dashed line are fitted background and P1 peak, respectively; (b) The Arrhenius plot of P1 peak for the Fe-18Ga-0.05La sample. M. Sun et al..
4
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with the decrease of Ga content. When the Ga content decreases by 1 at. %, the critical temperature decreases by 50 °C on average, indicating that the order-disorder phase transition temperature can be reduced by up to 100 °C when 1 at.% La is added. But the actual value should be lower than this value, because a small amount of La atoms may still be incorporated into the matrix. In order to further verify the relationship between Ptr IF peak and the Ga content in matrix, the IF-temperature spectra of Fe–Ga binary alloys with different Ga content are given in Fig. 8. It can be seen that the change of trace Ga content can lead to an opposite variation tendency of P1 peak and Ptr peak in the IF spectra: with the increase of Ga content, the Zener peak shifts to a lower temperature, while the Ptr IF peak shifts to a higher temperature. Through the calculation and analysis, the activation energies for the Fe-18.1Ga sample and the Fe19.3Ga sample are (3.0 ± 0.2) eV and (2.9 ± 0.2) eV, respectively. As a result, the P1 peak of the Fe-19.3Ga sample moves slightly toward a lower temperature compared with that of the Fe-18.1Ga sample. In addition, when the Ga content increases to 19.3 at.%, the relaxation magnitude of Zener peak decreases as a whole, which is mainly due to the ordering of D03 phase in the matrix, and thus resulting in the decrease of the nearest neighbor Ga–Ga dipole concentration. For the Ptr peak, combined with the order-disorder phase transition point (∼575 °C) of Fe-18.3Ga alloy [20], it can be seen that the Ptr peak increases with the increase of Ga content in a certain range without element doping. When the Ga content is higher than 21%, other ordered phases may occur during the order-disorder phase transition from D03 to A2, such as L12 and D019 phases, which may interfere with the Ptr peak and even lead to the disappearance of the Ptr peak. Therefore, when La is doped into the Fe − 18Ga binary alloy, the order-disorder phase transition point at high temperature will go down,
Table 1 The apparent activation enthalpy H of P1 peak, the peak position (TPtr) and the net peak height ( Q ptr1) of Ptr for Fe-18Ga-xLa (x = 0.05, 0.1, 0.2, 0.5, and 1.0 at.%) samples. Sample
P1
Ptr
H, eV
0.05 at.% La 0.1 at.% La 0.2 at.% La 0.5 at.% La 1.0 at.% La
3.0 2.9 2.8 3.0 2.9
± ± ± ± ±
0.2 0.2 0.2 0.2 0.2
TPtr ?oC (Heating/cooling)
(Heating, 1Hz)
571/526 561/523 557/515 523/481 504/470
0.40 0.18 0.16 0.09 0.08
1 Q Ptr , ×10
2
On the IF spectrum, the high temperature order-disorder phase transition peak (Ptr) is closely related to the D03 content at room temperature, and thus the net peak height of Ptr decreases. Fig. 6ab gives the macro and micro SEM images for Fe-18Ga − 1La, respectively. It can be seen that a large number of precipitates appear near the grain boundary. Through linear SEM-EDS analysis, the main component of the precipitate is LaGa2 after deducting the background as shown in Fig. 6c, which is in good agreement with the GI-XRD data. Therefore, the addition of La can deprive Ga atoms from the matrix, and one Ga atom can deprive two Ga atoms on average. For example, when 0.05, 0.2, 1 at.% Ga is doped into Fe–Ga alloys, the Ga content in the matrix can be reduced to 18.2, 17.9 and 16.3 at.% Ga at most (the original Ga content in the matrix is 18.3 at.%.). From the metastable phase diagram of Fe–Ga alloy as shown in Fig. 7, it can be seen that the critical temperature of order-disorder phase transition decreases rapidly
Fig. 4. (a) DSC heating curves for Fe-18Ga-xLa (x = 0.05, 0.1, 0.2, 0.5, and 1.0 at.%) samples, and the heating rate was 10 K/min; (b) La-doped content dependence of the critical temperature for the orderdisorder phase transition based on IF and heat flow tests. The solid and hollow data represent heating and cooling, respectively. M. Sun et al..
Fig. 5. (a) Grazing Incidence X-ray diffraction (GI-XRD) spectra (a) and enlarged GI-XRD spectra (b) for Fe-18Ga-xLa (x = 0.05, 0.2, and 1.0 at.%, respectively.) samples. M. Sun et al.. 5
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Fig. 6. Macro (a) and micro (b) SEM images for Fe-18Ga − 1La after annealing at 900 °C for 2 h; (c) Linear SEM-EDS analysis for precipitated phases on the grain boundary. M. Sun et al..
increase first and then almost remain stable with the increase of Ladoped content, and the average hardness remains near 5.36 GPa after the La-doped content reaches x = 0.2 at. %. Therefore, the trace La doping can not only reduce the critical temperature of high-temperature order-disorder phase transition, but also significantly improve the mechanical strength of the matrix, which is more conducive to practical application. 5. Conclusions The high-temperature order-disorder phase transition of Fe − 18Ga alloys doped by different La contents were carefully studied by a computer controlled automatic inverted torsion pendulum. With the increase of La-doped content, the Ptr peak gradually shifts to a lower temperature, and the peak strength gradually decreases. Combined with phase diagram, DSC curves, GI-XRD, and SEM, we find that when the La content increases, the LaGa2 structure phase gradually precipitates, resulting in the decrease of Ga content in the matrix. Thus, the critical temperature of D03→(B2)/A2 order-disorder phase transition shifts to a lower temperature, and the intensity of order-disorder transition is weakened. Furthermore, we have studied the IF spectra of Fe-18.1Ga and Fe-19.3Ga binary alloys. It is found that with the increase of Ga content, the Ptr peak gradually moves to a higher temperature, but the relaxation magnitude of the Zener peak decreases. At the same time, the addition of trace La can bring about a remarkable increase in the hardness of the Fe − 18Ga binary alloy, and the average hardness remains near 5.36 GPa after the La-doped content reaches x = 0.2 at. %. These results will be helpful to deepen the understanding of D03→(B2)/ A2 order-disorder phase transition in the Fe–Ga based alloys and to refine the preparation process to obtain the Fe-Ga-based alloy with high functional properties.
Fig. 7. Metastable phase diagram for Fe–Ga alloy [33]. M. Sun et al..
which is also suitable for Fe-(16–19)Ga alloys doped with other rare earth elements, such as Tb, Dy, Er [35–37]. These results will contribute to deepen the understanding of D03→A2 order-disorder phase transition in the Fe–Ga based alloys. Mechanical strength of Fe-18Ga-xLa (x = 0.05, 0.1, 0.2, 0.5, and 1.0 at.%) alloys annealed at 900 °C for 2 h under hydrogen atmosphere was investigated by nano-indentation hardness testing. Fig. 9 shows the variation trend of average hardness versus La-doped content. It can be seen that the addition of trace La can bring about a remarkable increase in the hardness of the Fe − 18Ga binary alloy. The average hardness
Fig. 8. Temperature dependence of IF curves with a temperature range of 300–700 °C for the Fe-18.1Ga (a) and Fe-19.3Ga (b) alloys, respectively. M. Sun et al.. 6
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Comp. 509 (32) (2011) 8165–8170. [11] I.S. Golovin, J. Cifre, Structural mechanisms of anelasticity in Fe–Ga-based alloys, J. Alloy. Comp. 584 (2014) 322–326. [12] I.S. Golovin, V.V. Palacheva, A.I. Bazlov, J. Cifre, J. Pons, Structure and anelasticity of Fe3Ga and Fe3(Ga, Al) type alloys, J. Alloy. Comp. 644 (2015) 959–967. [13] I.S. Golovin, V.V. Palacheva, A. Emdadi, D. Mari, A. Heintz, А.M. Balagurov, I.A. Bobrikov, Anelasticity of phase transitions and magnetostriction in Fe-(27-28%) Ga alloys, Mater. Res. 21 (2018). [14] M. Ishimoto, H. Numakura, M. Wuttig, Magnetoelastic damping in Fe–Ga solidsolution alloys, Mater. Sci. Eng. A 442 (1) (2006) 195–198. [15] I.S. Golovin, V.V. Palacheva, V.Y. Zadorozhnyy, J. Zhu, H. Jiang, J. Cifre, T.A. Lograsso, Influence of composition and heat treatment on damping and magnetostrictive properties of Fe–18%(Ga+ Al) alloys, Acta Mater. 78 (2014) 93–102. [16] A.A. Emdadi, J. Cifre, O.Y. Dementeva, I.S. Golovin, Effect of heat treatment on ordering and functional properties of the Fe–19Ga alloy, J. Alloy. Comp. 619 (2015) 58–65. [17] S.A.E. Boyer, M. Gerland, A. Rivière, J. Cifre, V.V. Palacheva, A.V. Mikhaylovskaya, I.S. Golovin, Anelasticity of the Fe-Ga alloys in the range of Zener relaxation, J. Alloy. Comp. 730 (2018) 424–433. [18] I.S. Golovin, A.M. Balagurov, W.C. Cheng, J. Cifre, D.A. Burdin, I.A. Bobrikov, V.V. Palacheva, N. Yu Samoylova, E.N. Zanaeva, In situ studies of atomic ordering in Fe-19Ga type alloys, Intermetallics 105 (2019) 6–12. [19] I.S. Golovin, V.V. Palacheva, J. Cifre, C. Jiang, Mechanical spectroscopy of Fe-Ga alloys at elevated temperatures, J. Alloy. Comp. 785 (2019) 1257–1263. [20] M. Sun, X.P. Wang, L. Wang, H. Wang, W.B. Jiang, W. Liu, T. Hao, R. Gao, Y.X. Gao, T. Zhang, L. Wang, Q.F. Fang, C.S. Liu, High-temperature order-disorder phase transition in Fe-18Ga alloy evaluated by internal friction method, J. Alloy. Comp. 750 (2018) 669–676. [21] M. Sun, X.P. Wang, W.B. Jiang, H. Wang, Y.X. Gao, T. Hao, L. Wang, Q.F. Fang, C.S. Liu, Correlation between thermal history and high-temperature order–disorder phase transition in Fe–18Ga alloy, Mater. Lett. 239 (2019) 147–150. [22] N. Rahman, J. Gou, X. Liu, T. Ma, M. Yan, Enhanced magnetostriction of Fe81Ga19 by approaching an instable phase boundary, Scripta Mater. 146 (2018) 200–203. [23] T.I. Fitchorov, S. Bennett, L. Jiang, G. Zhang, Z. Zhao, Y. Chen, V.G. Harris, Thermally driven large magnetoresistance and magnetostriction in multifunctional magnetic FeGa–Tb alloys, Acta Mater. 73 (2014) 19–26. [24] Y.K. He, X.Q. Ke, C.B. Jiang, N.H. Miao, H. Wang, Coey, J.M.D. Coey, Y.Z. Wang, H.B. Xu, Interaction of trace rare‐earth dopants and nanoheterogeneities induces giant magnetostriction in Fe-Ga alloys, Adv. Funct. Mater. 28 (20) (2018) 1800858. [25] T.Y. Yang, W. Wen, G.Z. Yin, X.L. Li, M. Gao, Y.L. Gu, L. Li, Y. Liu, H. Lin, X.M. Zhang, B. Zhao, T.K. Liu, Y.G. Yang, Z. Li, X.T. Zhou, X.Y. Gao, Introduction of the X-ray diffraction beamline of SSRF, Nucl. Sci. Tech. 26 (2015) 020101. [26] M. Gao, Y. Gu, L. Li, Z. Gong, X. Gao, W. Wen, Facile usage of a MYTHEN 1K with a Huber 5021 diffractometer and angular calibration in operando experiments, J. Appl. Crystallogr. 49 (2016) 1182–1189. [27] P.R. Bevington, Data Reduction and Error Analysis for the Physical Science, McGraw-Hill), New York, 1969, p. p235. [28] I.S. Golovin, A. Rivière, Mechanisms of anelasticity in Fe–13Ga alloy, Intermetallics 19 (4) (2011) 453–459. [29] M. Fang, J. Zhu, I.S. Golovin, J. Li, C. Yuan, X. Gao, Internal friction in (Fe80Ga20)99.95(NbC)0.05 alloy at elevated temperatures, Intermetallics 29 (2012) 133–139. [30] I.S. Golovin, Anelasticity of Fe–Ga based alloys, Mater. Des. 88 (2015) 577–587. [31] L.X. Yuan, Q.F. Fang, Nonlinear fitting of the internal friction data and its application on the bamboo grain boundary relaxation pure Al, Acta Met. Sinica 34 (1998) 1016–1020 (in Chinese). [32] A.S. Nowick, B.S. Berry, Anelastic Relaxation in Crystalline Solids, Academic Press, New York, 1972. [33] M. Hirscher, U. Brossmann, R. Henes, Measurement of the Zener relaxation in highpurity FeCr single crystals, Mater. Trans. 41 (1) (2000) 82–86. [34] O. Ikeda, R. Kainuma, I. Ohnuma, K. Fukamichi, K. Ishida, Phase equilibria and stability of ordered bcc phases in the Fe-rich portion of the Fe–Ga system, J. Alloy. Comp. 347 (1–2) (2002) 198–205. [35] C. Meng, H. Wang, Y. Wu, J. Liu, C. Jiang, Investigating enhanced mechanical properties in dual-phase Fe-Ga-Tb alloys, Sci. Rep. 6 (2016) 34258. [36] T. Jin, W. Wu, C. Jiang, Improved magnetostriction of Dy-doped Fe83Ga17 meltspun ribbons, Scripta Mater. 74 (2014) 100–103. [37] R. Barua, P. Taheri, Y. Chen, A. Koblischka-Veneva, M. Koblischka, L. Jiang, V. Harris, Giant enhancement of magnetostrictive response in directionally-solidified Fe83Ga17Erx compounds, Materials 11 (6) (2018) 1039.
Fig. 9. The variations of Vickers hardness versus La-doped content for Fe-18GaxLa (x = 0.05, 0.1, 0.2, 0.5, and 1.0 at.%, respectively.) samples. M. Sun et al..
Acknowledgements This work is supported by the National Key Research and Development Program of China (No. 2017YFA0402800) and the National Natural Science Foundation of China (Grant Nos. U1732121, 5171181, 1175255, 5171184, 11735015, 51801203). The authors also thank beamlines BL14B1 of SSRF (Shanghai Synchrotron Radiation Facility) for providing the beam time. References [1] A.E. Clark, J.B. Restorff, M. Wun-Fogle, T.A. Lograsso, D.L. Schlagel, Magnetostrictive properties of body-centered cubic Fe-Ga and Fe-Ga-Al alloys, IEEE Trans. Magn. 36 (5) (2000) 3238–3240. [2] N. Srisukhumbowornchai, S. Guruswamy, Large magnetostriction in directionally solidified FeGa and FeGaAl alloys, J. Appl. Phys. 90 (11) (2001) 5680–5688. [3] A.E. Clark, K.B. Hathaway, M. Wun-Fogle, J.B. Restorff, T.A. Lograsso, V.M. Keppens, G. Petculescu, R.A. Taylor, Extraordinary magnetoelasticity and lattice softening in bcc Fe-Ga alloys, J. Appl. Phys. 93 (10) (2003) 8621–8623. [4] T.A. Lograsso, A.R. Ross, D.L. Schlagel, A.E. Clark, M. Wun-Fogle, Structural transformations in quenched Fe–Ga alloys, J. Alloy. Comp. 350 (1–2) (2003) 95–101. [5] J. Boisse, H. Zapolsky, A.G. Khachaturyan, Atomic-scale modeling of nanostructure formation in Fe–Ga alloys with giant magnetostriction: cascade ordering and decomposition, Acta Mater. 59 (7) (2011) 2656–2668. [6] T.A. Lograsso, E.M. Summers, Detection and quantification of D03 chemical order in Fe–Ga alloys using high resolution X-ray diffraction, Mater. Sci. Eng. A 416 (1) (2006) 240–245. [7] S. Bhattacharyya, J.R. Jinschek, A. Khachaturyan, H. Cao, J.F. Li, D. Viehland, Nanodispersed DO3-phase nanostructures observed in magnetostrictive Fe–19%Ga Galfenol alloys, Phys. Rev. B 77 (10) (2008) 104107. [8] Y.K. He, C.B. Jiang, W. Wu, B. Wang, H.P. Duan, H. Wang, T.L. Zhang, J.M. Wang, J.H. Liu, Z.L. Zhang, P. Stamenov, J.M.D. Coey, H.B. Xu, Giant heterogeneous magnetostriction in Fe–Ga alloys: effect of trace element doping, Acta Mater. 109 (2016) 177–186. [9] I.S. Golovin, A.M. Balagurov, W.C. Cheng, J. Cifre, D.A. Burdin, I.A. Bobrikov, V.V. Palachevaa, N. Yu Samoylov, E.N. Zanaeva, In situ studies of atomic ordering in Fe-19Ga type alloys, Intermetallics 105 (2019) 6–12. [10] I.S. Golovin, Z. Belamri, D. Hamana, Internal friction, dilatometric and calorimetric study of anelasticity in Fe–13 at.% Ga and Fe–8 at.% Al–3 at.% Ga alloys, J. Alloy.
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Effect of La addition on high-temperature order-disorder phase transformation in Fe − 18Ga alloy
T
Meng Suna,b, Yinxing Wua,b, Weibin Jianga, Wang Liua, Xianping Wanga,∗, Yunxia Gaoa, Rui Liua, Ting Haoa, Wen Wenc,∗∗, Qianfeng Fanga a
Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei, 230031, PR China Department of Materials Science and Engineering, University of Science and Technology of China, Hefei, 230026, PR China c Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai, 201204, PR China b
ARTICLE INFO
ABSTRACT
Keywords: Internal friction Order-disorder LaGa2 Zener relaxation Hardness
The microstructure, internal friction (IF) behavior spectra, heat flow curves, and mechanical strength of Fe18Ga-xLa (x = 0.05, 0.1, 0.2, 0.5, and 1.0 at.%) alloys were systematically analyzed in this investigation. In the IF spectra, a relaxation IF peak (Labeled as P1) and a peak related to order-disorder phase transition (Labeled as Ptr) are observed in the temperature range of 400 °C–690 °C. It is found trace La doping has a significant effect on the Ptr peak. With the increase of the La-doped content, the peak of Ptr gradually shifts to a lower temperature and the net peak height decreases. Combining with phase diagram, DSC, Grazing Incidence X-ray diffraction (GIXRD) spectra and SEM, the mechanisms of the reduction of both the critical temperature and the strength of Ptr peak for the Fe-18Ga-xLa alloy are ascribed to the precipitation of LaGa2 phase, which reduces the Ga content gradually in the matrix. Further, the mechanism is verified in Fe-18.1Ga alloy and Fe-19.3Ga alloy. In addition, the trace La doping can significantly improve the mechanical strength of the Fe − 18Ga alloy.
1. Introduction The addition of non-magnetic Ga element to the body-centered cubic (b.c.c) α-Fe is known to yield extremely large magnetostrictive coefficient along [100] direction of λ100 > 260 ppm, with maxima occurring at 17–19 and 27 at.% Ga [1–3]. Recently, the unique magnetostrictive property of Fe − 18Ga alloy is mainly considered to originate from the nanosized tetragonal phase (L16 or L10), a phase of lower symmetry, which associated with order–disorder transition of Ga atoms in the matrix [4,5]. However, it is much difficult to distinguish this structure with the usual characterization methods, such as, X-ray diffraction (XRD), Scanning electron microscope (SEM), and Transmission electron microscopy (TEM), due to the little content and instability [6–8]. Therefore, the accurate and in situ characterization of order-disorder transition of Ga atoms in the matrix for Fe − 18Ga binary alloy is required to help us understand and tune mechanical properties and magnetostriction, which is beneficial for applications of microdisplacement control, energy-harvesters and spintronic devices [9]. IF behavior is particularly sensitive to the phase transition process and internal defects of solid materials. In the last few years, rich IF ∗
phenomena of Fe-Ga-based alloys were discovered due to phase structures, Ga–Ga atom pairs, and phase transitions [10–13]. M. Ishimoto et al. firstly studied the effect of temperature on the IF behaviors of Fe17 at.% Ga alloy, and found there was a high-damping plateau (up to 10−2) over the temperature range of -190-300 °C, which was ascribed to magnetoelastic hysteresis originating from the large magnetostriction [14]. Next, Golovin's group had done a lot of work on the mechanical spectra for Fe-(17–19) at.% Ga based alloy combined with neutron diffraction. Besides the high damping plateau below 300 °C, a phase transition IF peak near 450 °C caused by ordered b.c.c D03 (Fe3Ga, sp. gr. Fm3m) to face-centered cubic (f.c.c) L12 (Fe3Ga, sp. gr. Pm3 m) transition, a relaxational-type IF peak near 500 °C, and a weak frequency independent IF peak near 490 °C were also observed [15–18]. It worth noting that A.E. Boyer et al. proved that the relaxationaltype IF peak belongs to Zener peak rather than grain boundary relaxation peak through the Fe-17.4 at.% Ga single crystal IF experiment, and found that the relaxation magnitude for Fe–Ga binary alloy was proportional to concentration of Ga atoms up to 19 at.%, and then was followed by a pronounced decrease for the alloys with > 20 at.% Ga due to D03 and L12 ordering of Ga atoms in Fe–Ga alloys [17,19]. Besides the Zener relaxation peak, the frequency independent IF peaks
Corresponding author. Corresponding author. E-mail addresses: [email protected] (X. Wang), [email protected] (W. Wen).
∗∗
https://doi.org/10.1016/j.intermet.2019.106496 Received 8 April 2019; Received in revised form 29 April 2019; Accepted 4 May 2019 Available online 14 May 2019 0966-9795/ © 2019 Elsevier Ltd. All rights reserved.
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Fig. 1. (a) IF (T =2 K/min, f = 1 Hz, and ε = 3 × 10−5) versus temperature for the as-cast Fe − 18Ga alloy and the Fe-18Ga-0.1La alloy annealed at 900 °C in hydrogen atmosphere, respectively; (b) IF-behaviors of P1 and Ptr peaks after deducting the backgrounds. M. Sun et al..
(Ptr) near 575 °C were observed in our group, which is also particularly sensitive to D03 ordering of Ga atoms in the matrix [20,21]. And it is interesting that quenching from the temperature range of Ptr peaks can improve the magnetostriction of Fe − 18Ga based alloys significantly [20,22]. Therefore, a detailed study of the high-temperature ordering behaviors of Fe − 18Ga based alloys is helpful to design precise heattreatment methods to obtain high functional properties. In recent years, trace rare earth dopants was found can induce giant magnetostriction in Fe–Ga binary alloys [8,23,24]. Especially, 0.2 at.% La doping can produces the largest magnetostriction of up to ∼600 ppm, which was suggested to arise mainly from tetragonal distortion of lower symmetry nano-heterogeneities with fixed Ga–Ga pairs [24]. In this paper, The high-temperature order-disorder phase transition of Fe − 18Ga alloys doped by different La contents were carefully studied by IF spectra and heat flow curves. We found that with the increase of the La content, the critical temperature of high temperature order-disorder phase transition decreases gradually. Combined with phase diagram, GI-XRD spectra, and SEM, it was found that the mechanism of the reduction of the phase transition temperature induced by La doping was ascribed to the precipitation of LaGa2 phase, which reduced the Ga content gradually in the matrix. Furthermore, in order to verify the mechanism of the temperature reduction of the orderdisorder phase transition for Fe − 18Ga alloys doped by La, the IF spectra of Fe-18.1Ga and Fe-19.3Ga binary alloys were studied in detail. In addition, the mechanical strength of Fe-18Ga-xLa was also investigated. The obtained results will contribute to deepen the understanding of D03→A2 order-disorder phase transition in the Fe–Ga based alloys and provide references for the precise design of the preparation process of the Fe–Ga based alloy with high functional properties.
beamline BL14B1 can be found in Refs. [25,26]. The IF behaviors of samples were measured by a computer-controlled automatic inverted torsion pendulum with the force-vibration mode, in which different frequencies (0.2∼5 Hz) were carried out in one measurement run with a heating rate of 2 K/min over a temperature range from RT to 800 °C, then held for 10 min, and finally cooled at a speed of 2 K/min. The sample size in the IF measurement is about 2 × 1 × 23 mm3. The maximum torsion strain amplitude was kept at 3 × 10−5 in all measurements. The whole measuring process was carried out in vacuum (∼10Pa) to avoid oxidation at high temperature. Besides IF tests, differential scanning calorimetry curves (DSC, PerkinElmer, USA) were also carried out to measure the order-disorder phase transition temperatures at a heating/cooling rate of 10 K/min. All hardness tests were performed on the surfaces of Fe-18Ga-xLa samples using a Nano-Indenter G200 mechanical testing device (Agilent) with a displacement resolution of 0.01 nm/s and a strain rate of 0.05 s−1. Average hardness values were calculated from 12 to 17 separate indents, which obtained for contact depths between 1000 nm and 1500 nm, corresponding to a steady-state hardness value. All samples with the size of 10 × 10 × 2 mm3 were mechanically polished before testing to ensure the data stability. 3. Results 3.1. Descriptions of P1 and Ptr peaks Fig. 1a shows the IF-temperature spectra of as-cast Fe − 18Ga and Fe-18Ga-0.1La alloys, respectively. A high damping plateau is observed over the temperature range of RT to 230 °C, and then the IF value decreases rapidly to about 0.003. Besides the high damping plateau, there are two pronounced IF peaks (labeled as P1 at a lower temperature range and Ptr at a higher temperature range) over the temperature range from 300 to 700 °C. It should be noted that the as-cast Fe − 18Ga specimen was wire-cut from a large sample weighing 25 kg by arc melting, while the La-doped sample is wire-cut from a small sample weighing 50 g. Thus, the cooling rate of the small sample after melting is much higher than that of the as-cast Fe − 18Ga alloy, which causes the Ptr peak of the Fe − 18Ga specimen doped by La annealed in hydrogen to be lower than that of the as-cast Fe − 18Ga specimen. Blue and pink dashed lines are IF backgrounds (BGs) for the as-cast Fe − 18Ga alloy and the Fe-18Ga-0.1La alloy, respectively. It is known that an IF background (Qb 1), as a function of temperature (T), can be expressed as [27].
2. Experimental technique The ingots with nominal atomic composition Fe-18Ga-xLa (x = 0.05, 0.1, 0.2, 0.5, and 1.0 at.%) were produced in a vacuum arc melting furnace using pure Fe (99.99 wt%), pure Ga (99.99 wt%) and La (99.9 wt%) under Ar atmosphere. For comparative study, Fe-18.1Ga and Fe-19.3Ga binary alloys were also prepared. All compositions in this paper are indicated in atomic per cent. In order to prevent the burning loss during the smelting process, Ga and La elements have been weighed for 2% excess, and the mater ingots were melted for four times to ensure compositional homogeneity. In addition, all the samples were annealed at 900 °C for 2 h in hydrogen atmosphere before testing, and the cooling rate was 5 K/min. The microstructures were studied by Grazing Incidence X-ray diffraction (GI-XRD) spectra. The X-ray diffraction data were obtained at beamline BL14B1 of the Shanghai Synchrotron Radiation Facility (SSRF) with a wavelength of 0.6887 Å. The detailed information about
Qb 1 = A + Bexp ( C / kT ),
(1)
where A, B and C are constants and k is the Boltzmann constant. After the BG was subtracted from the curves, the IF-behaviors of P1 and Ptr 2
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peaks are shown in Fig. 1b. P1 peak: The establishment of the formation mechanism for P1 peak experienced a tortuous process. In Fe − 13Ga alloy, Golovin et al. first observed that P1 peak was located near 500 °C and the mechanism was suggested to originate from grain boundary relaxation, while Zener peak was suggested to be located at a lower temperature, and the peak was a process IF peak: the peak appeared during the heating process and disappeared during the cooling process. It was considered that the ordering of Ga atoms in the matrix during the cooling process led to the disappearance of Zener peak [10]. With the further study of the IF spectra of Fe − 13Ga specimens, different heat-treatment conditions also had a weak influence on the P1 peak. Therefore, it was suggested that the peak was originated from Zener relaxation, while the activation energy of the process peak was only 0.85 eV and disappeared after annealed at 350 °C. Thus, the mechanism of the process peak was suggested to be dislocation movement, and the relaxation peak caused by the grain boundary was pushed toward the IF peak at a higher temperature [28]. Fang et al. conducted a preliminary study on the IFtemperature spectrum of Fe(Fe80Ga20)99.95(NbC)0.05 alloy. It was also considered that the P1 peak was Zener peak, and the higher temperature peak was suggested as the grain boundary peak based on activation energy [29]. However, the grain boundary peak at a high temperature was not observed in the Fe − 17Ga alloy, and thus the process peak was again recognized as the Zener peak, and the P1 peak was regarded as the grain boundary peak [11]. Further in the study of Fe-18(Ga + Al) alloys, the mechanism of the P1 peak was re-identified as a result of Zener or grain boundary relaxation [15]. Since the P1 peak was not clearly observed in both Fe − 3Ga and Fe − 27Ga, the mechanism of the P1 peak tends to be the Zener relaxation [30]. Further, through the IF experiments for the Fe-17.4Ga single crystal and the Fe–Ga polycrystalline samples with 8–33 at.% Ga, it was found that the P1 peak was still present in the IF spectrum of Fe-17.4Ga single crystal. With the increase of Ga content, the relaxation magnitude gradually increases. After the Ga content reaches 17–19 at.%, the relaxation magnitude decreases rapidly, and disappears when the Ga content reaches to 23–25 at.% [17,19]. These phenomena basically confirm that the mechanism of P1 peak is Zener relaxation. Ptr peak: It can be seen that the IF spectrum for the Fe − 18Ga alloy has a broad IF peak as shown in Fig. 1b, which can be divided into two subpeaks: Ptr1 at a lower temperature and Ptr2 at a higher temperature. In previous studies, we suggested that the formation mechanisms of these two IF peaks originated from D03→(B2) and (B2)→A2, respectively [20]. In the IF spectrum of the Fe − 18Ga specimen doped by La, the Ptr peak for the Fe − 18Ga specimen doped by La is asymmetric after deducting the high temperature IF background. Thus, besides the significant Ptr1 peak, the Ptr2 peak also exists. However, it is difficult to determine the specific transition point of the (B2)→A2 phase transition due to the difficulty of the fitting of the composite Ptr peak, and in this paper, we will discuss the whole Ptr peak caused by order-disorder phase transition D03→(B2)/A2 instead of discussing the Ptr1 and the Ptr2 peak separately. From Fig. 1b, it can be seen that the Ptr peak position shift to a lower temperature when Fe − 18Ga alloy is doped with 0.1 at.% La, which indicates that trace La doping has a significant effect on the Ptr peak position.
peak position of P1 does not change significantly, but the peak position of Ptr decreased gradually from 571 °C to 504 °C. It is noteworthy that the peak strengths of P1 and Ptr seem to increase with the increase of La content, but this phenomenon is not real because the two peaks interfere with each other as the Ptr peak approaches the P1 peak. As for the high damping plateau that mainly originated from magneto-mechanical hysteresis [11], the increase in the La-doped content does not significantly enhance the damping capacity (f = 3 Hz, ε = 3 × 10−5) of Fe-18Ga-xLa alloys, or even there is a slight decrease. P1 peak is attribute to Zener relaxation as described in Ref. [17], and the effects of trace La doping on the peak strength and position are not obvious. The Ptr peak is a frequency-independent IF peak that exhibiting a typical characteristic of a phase transition. Herein, the mechanism of the Ptr peak is suggested to the D03→(B2)/A2 phase transition, because the IF peak induced by (B2)→A2 phase transition is difficult to separate from the whole Ptr peak. As the La content increases, the Ptr peak gradually shifts to a lower temperature, indicating the doping of La will have a significant effect on the order-disorder phase transition. The corresponding mechanism will be further discussed combined with Grazing Incidence X-ray diffraction (GI-XRD) results in the following sections. Fig. 3a shows an example of P1 peak fitting and the estimation method of the net Ptr peak height ( Q Ptr1) for the Fe-18Ga-0.05La sample measured at 1 and 3 Hz, respectively. The IF curve with relaxation mechanism can be well fitted by one or more Debye peaks and background based on a non-liner fitting method [31]. Thus the peak temperature at different measurement frequencies can be precisely determined. For the Debye peak, it can be expressed by the equation for IF [32]
Q
1
=
1+
2 2
=
e
x
1 , + ex
(2)
where Δ is the relaxation strength, is the relaxation time, w is the circular frequency (=2πf, f is the measuring frequency), and x = In ( ). The can be expressed as
=
0 exp(H / kT ),
(3)
where 0 is the pre-exponential factor, H is the activation energy, k is Boltzmann constant, and T is the absolute temperature. Thus, the = 1, and Debye peak is maximum of Debye peak occurs when symmetrical in 1/T scale. With the net peak temperatures at different frequencies, the apparent activation enthalpy H can be evaluated accurately. Fig. 3b shows the Arrhenius plots (natural logarithm of circular frequency ω versus the reciprocal of net peak temperature 1/TP ) for the Fe-18Ga-0.05La sample. The relaxation activation energy H is determined as (3.0 ± 0.2) eV, which is close to the reported results of Zener relaxation in Fe-Ga-Al or Fe–Cr system [15,33]. The relaxation parameters of P1 peaks, the peak positions and the net peak heights of Ptr peaks for Fe-18Ga-xLa (x = 0.05, 0.1, 0.2, 0.5, and 1.0 at. %) samples are shown in Table 1. There are three points worthy of attention: Firstly, with the increase of La content, the activation energy and peak position of P1 IF peak basically remains unchanged. Next, with the increase of Ga content, the IF peak temperature of Ptr peak shifts to a lower temperature regardless of the heating or cooling process. Finally, the peak strength of Ptr peak decreases gradually with the increase of La-doped content during the heating process.
3.2. IF-temperature spectra Fig. 2a–e shows the variations of IF versus temperature for Fe-18GaxLa (x = 0.05, 0.1, 0.2, 0.5, and 1.0 at.%) samples at five different vibration frequencies, the heating rate and the test amplitude were maintained at 2 K/min, 3 × 10−5, respectively. It can be seen from Fig. 2a–e that a high damping plateau with IF value of 0.01 is observed over the temperature range of RT to 230 °C, and then the IF value decreases rapidly to about 0.003. Besides the high damping plateau, the Ptr peak shows obvious asymmetry, suggesting that it is a compound IF peak. With the increase of La content from 0.05 at.% to 1.0 at.%, the
3.3. Heat-flow curves Fig. 4a shows the heat flow curves for Fe-18Ga-xLa samples. An obvious step at around 500 °C and a sharp endothermic peak around 690 °C were observed. The former corresponds well to the Ptr peak related to order-disorder phase transition, and the latter corresponds to the ferro-paramagnetic transition temperature (Tc). With the increase of La-doped content, it can be seen that the step temperature related to 3
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Fig. 2. (a–e) Temperature dependence of the IF (Q−1) for continuous heating for Fe-18Ga-xLa (x = 0.05, 0.1, 0.2, 0.5, and 1.0 at.%, respectively.) samples at five different frequencies of 0.2, 0.5, 1, 3, and 5 Hz. M. Sun et al..
the Ptr peak decreases gradually, while Curie temperature point tends to move slightly to a higher temperature. Fig. 4b shows the variation of order-disorder phase transition point with La-doped content during heating and cooling processes. It can be clearly seen that DSC data are in good agreement with the IF results, and there are obvious thermal hysteresis with the temperature difference of about 40 °C.
on the surface of the material, so it should not be used as a criterion for the precipitation of the second phase. In order to further explore the phase structure distribution in the material, the high-resolution amplification curves of GI-XRD spectra between 10 and 30° are given in Fig. 5b. Compared with the standard diffraction peaks, LaGa2 structure phase is observed in all Fe-18Ga-xLa samples besides A2 and D03 phases. For the Fe-18Ga-xLa alloys, as the La-doped content increases, more LaGa2 structural phases are formed gradually, resulting in a decrease in Ga content in the matrix. On the one hand, the decrease in Ga content will lower the critical temperature of D03→A2 order-disorder phase transition according to the metastable phase diagram [34]. On the other hand, according to the lever principle, after the same preparation process and heat treatment, the decrease of Ga content in the matrix leads to a decrease in the relative content of D03 at room temperature.
4. Discussion Fig. 5a shows the GI-XRD profiles for Fe-18Ga-xLa (x = 0.05, 0.2, and 1.0 at.%, respectively) samples. The basic diffraction peaks are (110), (200), and (211), respectively, and all samples exhibit the similar cubic structure as α-Fe. Since GI-XRD spectrum is especially sensitive to the microstructure and stress distribution in the alloy, and the peak splitting observed at the high angle (211) is mainly caused by the stress
Fig. 3. (a) Temperature dependence of IF (Q−1) for an Fe-18Ga-0.05La sample measured at 1 and 3 Hz, respectively. The symbols are experimental data points and solid lines are the total fitting curves. The dotted line and dashed line are fitted background and P1 peak, respectively; (b) The Arrhenius plot of P1 peak for the Fe-18Ga-0.05La sample. M. Sun et al..
4
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with the decrease of Ga content. When the Ga content decreases by 1 at. %, the critical temperature decreases by 50 °C on average, indicating that the order-disorder phase transition temperature can be reduced by up to 100 °C when 1 at.% La is added. But the actual value should be lower than this value, because a small amount of La atoms may still be incorporated into the matrix. In order to further verify the relationship between Ptr IF peak and the Ga content in matrix, the IF-temperature spectra of Fe–Ga binary alloys with different Ga content are given in Fig. 8. It can be seen that the change of trace Ga content can lead to an opposite variation tendency of P1 peak and Ptr peak in the IF spectra: with the increase of Ga content, the Zener peak shifts to a lower temperature, while the Ptr IF peak shifts to a higher temperature. Through the calculation and analysis, the activation energies for the Fe-18.1Ga sample and the Fe19.3Ga sample are (3.0 ± 0.2) eV and (2.9 ± 0.2) eV, respectively. As a result, the P1 peak of the Fe-19.3Ga sample moves slightly toward a lower temperature compared with that of the Fe-18.1Ga sample. In addition, when the Ga content increases to 19.3 at.%, the relaxation magnitude of Zener peak decreases as a whole, which is mainly due to the ordering of D03 phase in the matrix, and thus resulting in the decrease of the nearest neighbor Ga–Ga dipole concentration. For the Ptr peak, combined with the order-disorder phase transition point (∼575 °C) of Fe-18.3Ga alloy [20], it can be seen that the Ptr peak increases with the increase of Ga content in a certain range without element doping. When the Ga content is higher than 21%, other ordered phases may occur during the order-disorder phase transition from D03 to A2, such as L12 and D019 phases, which may interfere with the Ptr peak and even lead to the disappearance of the Ptr peak. Therefore, when La is doped into the Fe − 18Ga binary alloy, the order-disorder phase transition point at high temperature will go down,
Table 1 The apparent activation enthalpy H of P1 peak, the peak position (TPtr) and the net peak height ( Q ptr1) of Ptr for Fe-18Ga-xLa (x = 0.05, 0.1, 0.2, 0.5, and 1.0 at.%) samples. Sample
P1
Ptr
H, eV
0.05 at.% La 0.1 at.% La 0.2 at.% La 0.5 at.% La 1.0 at.% La
3.0 2.9 2.8 3.0 2.9
± ± ± ± ±
0.2 0.2 0.2 0.2 0.2
TPtr ?oC (Heating/cooling)
(Heating, 1Hz)
571/526 561/523 557/515 523/481 504/470
0.40 0.18 0.16 0.09 0.08
1 Q Ptr , ×10
2
On the IF spectrum, the high temperature order-disorder phase transition peak (Ptr) is closely related to the D03 content at room temperature, and thus the net peak height of Ptr decreases. Fig. 6ab gives the macro and micro SEM images for Fe-18Ga − 1La, respectively. It can be seen that a large number of precipitates appear near the grain boundary. Through linear SEM-EDS analysis, the main component of the precipitate is LaGa2 after deducting the background as shown in Fig. 6c, which is in good agreement with the GI-XRD data. Therefore, the addition of La can deprive Ga atoms from the matrix, and one Ga atom can deprive two Ga atoms on average. For example, when 0.05, 0.2, 1 at.% Ga is doped into Fe–Ga alloys, the Ga content in the matrix can be reduced to 18.2, 17.9 and 16.3 at.% Ga at most (the original Ga content in the matrix is 18.3 at.%.). From the metastable phase diagram of Fe–Ga alloy as shown in Fig. 7, it can be seen that the critical temperature of order-disorder phase transition decreases rapidly
Fig. 4. (a) DSC heating curves for Fe-18Ga-xLa (x = 0.05, 0.1, 0.2, 0.5, and 1.0 at.%) samples, and the heating rate was 10 K/min; (b) La-doped content dependence of the critical temperature for the orderdisorder phase transition based on IF and heat flow tests. The solid and hollow data represent heating and cooling, respectively. M. Sun et al..
Fig. 5. (a) Grazing Incidence X-ray diffraction (GI-XRD) spectra (a) and enlarged GI-XRD spectra (b) for Fe-18Ga-xLa (x = 0.05, 0.2, and 1.0 at.%, respectively.) samples. M. Sun et al.. 5
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Fig. 6. Macro (a) and micro (b) SEM images for Fe-18Ga − 1La after annealing at 900 °C for 2 h; (c) Linear SEM-EDS analysis for precipitated phases on the grain boundary. M. Sun et al..
increase first and then almost remain stable with the increase of Ladoped content, and the average hardness remains near 5.36 GPa after the La-doped content reaches x = 0.2 at. %. Therefore, the trace La doping can not only reduce the critical temperature of high-temperature order-disorder phase transition, but also significantly improve the mechanical strength of the matrix, which is more conducive to practical application. 5. Conclusions The high-temperature order-disorder phase transition of Fe − 18Ga alloys doped by different La contents were carefully studied by a computer controlled automatic inverted torsion pendulum. With the increase of La-doped content, the Ptr peak gradually shifts to a lower temperature, and the peak strength gradually decreases. Combined with phase diagram, DSC curves, GI-XRD, and SEM, we find that when the La content increases, the LaGa2 structure phase gradually precipitates, resulting in the decrease of Ga content in the matrix. Thus, the critical temperature of D03→(B2)/A2 order-disorder phase transition shifts to a lower temperature, and the intensity of order-disorder transition is weakened. Furthermore, we have studied the IF spectra of Fe-18.1Ga and Fe-19.3Ga binary alloys. It is found that with the increase of Ga content, the Ptr peak gradually moves to a higher temperature, but the relaxation magnitude of the Zener peak decreases. At the same time, the addition of trace La can bring about a remarkable increase in the hardness of the Fe − 18Ga binary alloy, and the average hardness remains near 5.36 GPa after the La-doped content reaches x = 0.2 at. %. These results will be helpful to deepen the understanding of D03→(B2)/ A2 order-disorder phase transition in the Fe–Ga based alloys and to refine the preparation process to obtain the Fe-Ga-based alloy with high functional properties.
Fig. 7. Metastable phase diagram for Fe–Ga alloy [33]. M. Sun et al..
which is also suitable for Fe-(16–19)Ga alloys doped with other rare earth elements, such as Tb, Dy, Er [35–37]. These results will contribute to deepen the understanding of D03→A2 order-disorder phase transition in the Fe–Ga based alloys. Mechanical strength of Fe-18Ga-xLa (x = 0.05, 0.1, 0.2, 0.5, and 1.0 at.%) alloys annealed at 900 °C for 2 h under hydrogen atmosphere was investigated by nano-indentation hardness testing. Fig. 9 shows the variation trend of average hardness versus La-doped content. It can be seen that the addition of trace La can bring about a remarkable increase in the hardness of the Fe − 18Ga binary alloy. The average hardness
Fig. 8. Temperature dependence of IF curves with a temperature range of 300–700 °C for the Fe-18.1Ga (a) and Fe-19.3Ga (b) alloys, respectively. M. Sun et al.. 6
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Comp. 509 (32) (2011) 8165–8170. [11] I.S. Golovin, J. Cifre, Structural mechanisms of anelasticity in Fe–Ga-based alloys, J. Alloy. Comp. 584 (2014) 322–326. [12] I.S. Golovin, V.V. Palacheva, A.I. Bazlov, J. Cifre, J. Pons, Structure and anelasticity of Fe3Ga and Fe3(Ga, Al) type alloys, J. Alloy. Comp. 644 (2015) 959–967. [13] I.S. Golovin, V.V. Palacheva, A. Emdadi, D. Mari, A. Heintz, А.M. Balagurov, I.A. Bobrikov, Anelasticity of phase transitions and magnetostriction in Fe-(27-28%) Ga alloys, Mater. Res. 21 (2018). [14] M. Ishimoto, H. Numakura, M. Wuttig, Magnetoelastic damping in Fe–Ga solidsolution alloys, Mater. Sci. Eng. A 442 (1) (2006) 195–198. [15] I.S. Golovin, V.V. Palacheva, V.Y. Zadorozhnyy, J. Zhu, H. Jiang, J. Cifre, T.A. Lograsso, Influence of composition and heat treatment on damping and magnetostrictive properties of Fe–18%(Ga+ Al) alloys, Acta Mater. 78 (2014) 93–102. [16] A.A. Emdadi, J. Cifre, O.Y. Dementeva, I.S. Golovin, Effect of heat treatment on ordering and functional properties of the Fe–19Ga alloy, J. Alloy. Comp. 619 (2015) 58–65. [17] S.A.E. Boyer, M. Gerland, A. Rivière, J. Cifre, V.V. Palacheva, A.V. Mikhaylovskaya, I.S. Golovin, Anelasticity of the Fe-Ga alloys in the range of Zener relaxation, J. Alloy. Comp. 730 (2018) 424–433. [18] I.S. Golovin, A.M. Balagurov, W.C. Cheng, J. Cifre, D.A. Burdin, I.A. Bobrikov, V.V. Palacheva, N. Yu Samoylova, E.N. Zanaeva, In situ studies of atomic ordering in Fe-19Ga type alloys, Intermetallics 105 (2019) 6–12. [19] I.S. Golovin, V.V. Palacheva, J. Cifre, C. Jiang, Mechanical spectroscopy of Fe-Ga alloys at elevated temperatures, J. Alloy. Comp. 785 (2019) 1257–1263. [20] M. Sun, X.P. Wang, L. Wang, H. Wang, W.B. Jiang, W. Liu, T. Hao, R. Gao, Y.X. Gao, T. Zhang, L. Wang, Q.F. Fang, C.S. Liu, High-temperature order-disorder phase transition in Fe-18Ga alloy evaluated by internal friction method, J. Alloy. Comp. 750 (2018) 669–676. [21] M. Sun, X.P. Wang, W.B. Jiang, H. Wang, Y.X. Gao, T. Hao, L. Wang, Q.F. Fang, C.S. Liu, Correlation between thermal history and high-temperature order–disorder phase transition in Fe–18Ga alloy, Mater. Lett. 239 (2019) 147–150. [22] N. Rahman, J. Gou, X. Liu, T. Ma, M. Yan, Enhanced magnetostriction of Fe81Ga19 by approaching an instable phase boundary, Scripta Mater. 146 (2018) 200–203. [23] T.I. Fitchorov, S. Bennett, L. Jiang, G. Zhang, Z. Zhao, Y. Chen, V.G. Harris, Thermally driven large magnetoresistance and magnetostriction in multifunctional magnetic FeGa–Tb alloys, Acta Mater. 73 (2014) 19–26. [24] Y.K. He, X.Q. Ke, C.B. Jiang, N.H. Miao, H. Wang, Coey, J.M.D. Coey, Y.Z. Wang, H.B. Xu, Interaction of trace rare‐earth dopants and nanoheterogeneities induces giant magnetostriction in Fe-Ga alloys, Adv. Funct. Mater. 28 (20) (2018) 1800858. [25] T.Y. Yang, W. Wen, G.Z. Yin, X.L. Li, M. Gao, Y.L. Gu, L. Li, Y. Liu, H. Lin, X.M. Zhang, B. Zhao, T.K. Liu, Y.G. Yang, Z. Li, X.T. Zhou, X.Y. Gao, Introduction of the X-ray diffraction beamline of SSRF, Nucl. Sci. Tech. 26 (2015) 020101. [26] M. Gao, Y. Gu, L. Li, Z. Gong, X. Gao, W. Wen, Facile usage of a MYTHEN 1K with a Huber 5021 diffractometer and angular calibration in operando experiments, J. Appl. Crystallogr. 49 (2016) 1182–1189. [27] P.R. Bevington, Data Reduction and Error Analysis for the Physical Science, McGraw-Hill), New York, 1969, p. p235. [28] I.S. Golovin, A. Rivière, Mechanisms of anelasticity in Fe–13Ga alloy, Intermetallics 19 (4) (2011) 453–459. [29] M. Fang, J. Zhu, I.S. Golovin, J. Li, C. Yuan, X. Gao, Internal friction in (Fe80Ga20)99.95(NbC)0.05 alloy at elevated temperatures, Intermetallics 29 (2012) 133–139. [30] I.S. Golovin, Anelasticity of Fe–Ga based alloys, Mater. Des. 88 (2015) 577–587. [31] L.X. Yuan, Q.F. Fang, Nonlinear fitting of the internal friction data and its application on the bamboo grain boundary relaxation pure Al, Acta Met. Sinica 34 (1998) 1016–1020 (in Chinese). [32] A.S. Nowick, B.S. Berry, Anelastic Relaxation in Crystalline Solids, Academic Press, New York, 1972. [33] M. Hirscher, U. Brossmann, R. Henes, Measurement of the Zener relaxation in highpurity FeCr single crystals, Mater. Trans. 41 (1) (2000) 82–86. [34] O. Ikeda, R. Kainuma, I. Ohnuma, K. Fukamichi, K. Ishida, Phase equilibria and stability of ordered bcc phases in the Fe-rich portion of the Fe–Ga system, J. Alloy. Comp. 347 (1–2) (2002) 198–205. [35] C. Meng, H. Wang, Y. Wu, J. Liu, C. Jiang, Investigating enhanced mechanical properties in dual-phase Fe-Ga-Tb alloys, Sci. Rep. 6 (2016) 34258. [36] T. Jin, W. Wu, C. Jiang, Improved magnetostriction of Dy-doped Fe83Ga17 meltspun ribbons, Scripta Mater. 74 (2014) 100–103. [37] R. Barua, P. Taheri, Y. Chen, A. Koblischka-Veneva, M. Koblischka, L. Jiang, V. Harris, Giant enhancement of magnetostrictive response in directionally-solidified Fe83Ga17Erx compounds, Materials 11 (6) (2018) 1039.
Fig. 9. The variations of Vickers hardness versus La-doped content for Fe-18GaxLa (x = 0.05, 0.1, 0.2, 0.5, and 1.0 at.%, respectively.) samples. M. Sun et al..
Acknowledgements This work is supported by the National Key Research and Development Program of China (No. 2017YFA0402800) and the National Natural Science Foundation of China (Grant Nos. U1732121, 5171181, 1175255, 5171184, 11735015, 51801203). The authors also thank beamlines BL14B1 of SSRF (Shanghai Synchrotron Radiation Facility) for providing the beam time. References [1] A.E. Clark, J.B. Restorff, M. Wun-Fogle, T.A. Lograsso, D.L. Schlagel, Magnetostrictive properties of body-centered cubic Fe-Ga and Fe-Ga-Al alloys, IEEE Trans. Magn. 36 (5) (2000) 3238–3240. [2] N. Srisukhumbowornchai, S. Guruswamy, Large magnetostriction in directionally solidified FeGa and FeGaAl alloys, J. Appl. Phys. 90 (11) (2001) 5680–5688. [3] A.E. Clark, K.B. Hathaway, M. Wun-Fogle, J.B. Restorff, T.A. Lograsso, V.M. Keppens, G. Petculescu, R.A. Taylor, Extraordinary magnetoelasticity and lattice softening in bcc Fe-Ga alloys, J. Appl. Phys. 93 (10) (2003) 8621–8623. [4] T.A. Lograsso, A.R. Ross, D.L. Schlagel, A.E. Clark, M. Wun-Fogle, Structural transformations in quenched Fe–Ga alloys, J. Alloy. Comp. 350 (1–2) (2003) 95–101. [5] J. Boisse, H. Zapolsky, A.G. Khachaturyan, Atomic-scale modeling of nanostructure formation in Fe–Ga alloys with giant magnetostriction: cascade ordering and decomposition, Acta Mater. 59 (7) (2011) 2656–2668. [6] T.A. Lograsso, E.M. Summers, Detection and quantification of D03 chemical order in Fe–Ga alloys using high resolution X-ray diffraction, Mater. Sci. Eng. A 416 (1) (2006) 240–245. [7] S. Bhattacharyya, J.R. Jinschek, A. Khachaturyan, H. Cao, J.F. Li, D. Viehland, Nanodispersed DO3-phase nanostructures observed in magnetostrictive Fe–19%Ga Galfenol alloys, Phys. Rev. B 77 (10) (2008) 104107. [8] Y.K. He, C.B. Jiang, W. Wu, B. Wang, H.P. Duan, H. Wang, T.L. Zhang, J.M. Wang, J.H. Liu, Z.L. Zhang, P. Stamenov, J.M.D. Coey, H.B. Xu, Giant heterogeneous magnetostriction in Fe–Ga alloys: effect of trace element doping, Acta Mater. 109 (2016) 177–186. [9] I.S. Golovin, A.M. Balagurov, W.C. Cheng, J. Cifre, D.A. Burdin, I.A. Bobrikov, V.V. Palachevaa, N. Yu Samoylov, E.N. Zanaeva, In situ studies of atomic ordering in Fe-19Ga type alloys, Intermetallics 105 (2019) 6–12. [10] I.S. Golovin, Z. Belamri, D. Hamana, Internal friction, dilatometric and calorimetric study of anelasticity in Fe–13 at.% Ga and Fe–8 at.% Al–3 at.% Ga alloys, J. Alloy.
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