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. 2023 May 19;8(22):19892–19899. doi: 10.1021/acsomega.3c01823

Effect of Cr-Doping on the Structural and Magnetic Properties of Mechanically Alloyed FeCoNiAlMn1–xCrx High-Entropy Alloy Powder

Danial Nawaid Siddiqui †, Nasir Mehboob ‡,*, Abid Zaman ‡,*, Amnah Mohammed Alsuhaibani §, Ali Algahtani ∥,⊥, Vineet Tirth ∥,⊥, Sarah Alharthi #,, Nora Hamad Al-Shaalan ∇, Mohammed A Amin #
PMCID: PMC10249117  PMID: 37305269

Abstract

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In this work, the new compositions of FeCoNiAlMn1–xCrx, (0.0 ≤ x ≤ 1.0), a high-entropy alloy powder (HEAP), are prepared by mechanical alloying (MA). The influence of Cr doping on the phase structure, microstructure, and magnetic properties is thoroughly investigated through X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometry. It is found that this alloy has formed a simple body-centered cubic structure with a minute face-centered cubic structure for Mn to Cr replacement with heat treatment. The lattice parameter, average crystallite size, and grain size decrease by replacing Cr with Mn. The SEM analysis of FeCoNiAlMn showed no grain boundary formation, depicting a single-phase microstructure after MA, similar to XRD. The saturation magnetization first increases (68 emu/g) up to x = 0.6 and then decreases with complete substitution of Cr. Magnetic properties are related to crystallite size. FeCoNiAlMn0.4Cr0.6 HEAP has shown optimum results with better saturation magnetization and coercivity as a soft magnet.

Introduction

Regarding alloy design, previous studies have shown that the addition of more elements in an alloy leads to the formation of intermetallic compounds with poor physical properties. Recently, this concept regarding alloys has been challenged by high-entropy alloys (HEAs), which were first proposed by Yeh et al.1,2 HEAs are defined as alloys consisting of minimum five principal elements with the concentration of each between 5 and 35%. The HEA tends to form simple solid solution structures instead of intermetallic compounds due to high mixing entropy consisting of face-centered cubic (FCC) and body-centered cubic (BCC) phases. Traditionally, alloy design exploits the boundaries of multi-component phase diagrams, whereas HEA composition focuses on the center of the phase diagram.3 This broadens the compositional space by introducing a variety of material properties that are yet to be investigated. The study on HEAs up to this point has been predicated on their use as structural materials, which can vary in composition and manufacturing conditions.4 Due to its functional qualities, such as corrosion,5 hydrogen storage,6 thermoelectric,7 superconducting,8 magneto caloric,9 and soft magnetism,10 HEAs are gaining attention as functional materials.

Most of the reported studies on HEA preparation involve a liquid processing method like arc melting.11 Murty et al.12 prepared AlCoFeMnNi HEA by casting vacuum arc melting and thereafter formed B2 phase. Similarly, mechanical alloying (MA), a solid-state powder process, is widely used for producing solid solution structures at the nanoscale with unusual properties,13 being an alternate route instead of arc melting and casting for producing HEAs.14 Gómez-Esparza et al.15 prepared the FeCoNiAlCr high-entropy alloy powder (HEAP) by MA, and thereafter, 10 h of milling the same has shown a mixture of solid solution phases of FCC and BCC.

Soft magnetic materials should have high saturation magnetization (Ms) and low magnetic coercivity (Hc) with their application in transformer cores and signal processing equipment like controls and transducers.16 The current research on HEAs has revealed that in addition to having outstanding mechanical properties, these alloys also exhibit good soft magnetic properties.17,18 Zuo et al.18 reported that magnetic HEA AlCoFeMnNi (as-cast) alloy showed a high Ms value of about 148.7 emu/g, while CoFeMnNi (as-cast) had a low Ms of 18.14 emu/g. Therefore, adding Al enhanced its saturation magnetization significantly. A novel soft magnetic material should be developed for meeting the growing performance and technical needs in the field of electronics. The emergence of HEAs opens up new possibilities for creating novel soft magnetic materials.16−18 The soft magnetic characteristics of HEAs made of ferromagnetic materials (Fe, Co, and Ni) are typically quite good. For example, CoFeMn0.25NiAl0.2517 and CoFeMnNiGa18 alloys have high saturation magnetization (101 and 116 emu/g) and low coercivity (3.4 and 28 Oe), respectively. Similarly, the AlxCoCrFeNi alloy is being widely studied to elucidate its micro structural, mechanical,19 anti-corrosive,20 and thermal expansion properties.21 However, its magnetic properties have not been fully explored yet. For instance, the recent measurement of magnetization has shown that the magnetic state of the equimolar alloy FeCrCoNiAlx progressively changes from paramagnetic to ferromagnetic at ambient temperature when Al is added.22

The phase structure and magnetic properties of HEAs are also affected by heat treatment. Karati et al.12 observed that casted AlCoFeMnNi alloy is transformed from the B2 to the BCC + FCC phase after heating for 50 h at 1050 °C, thereby increasing the wider applicability of the alloy by elimination of the brittle intermetallic compound phase. Yang et al.23 studied that Ms of AlCoFeMnNi decreases upon heating at relatively low temperatures but increases upon heating at a temperature of 900 °C and above. Duan et al.24 investigated the phase structure and magnetic properties of the FeCoNiAlCrx alloy powders with different Cr contents prepared by MA and then heating at 500 °C for increasing the crystallinity and reducing residual stress. In this alloy system, mixed FCC and BCC phases were observed after heating. Before heating, Ms ranged between 89.88 and 74.94 emu/g but after heating, Ms increased ranging between 98.69 and 83.04 emu/g. Since the phase structure and magnetic properties vary with heat treatment, it is necessary to probe its influence on the phase structure and magnetic properties of the synthesized HEAP.

In the present study, an effort is made to synthesize and to observe the effect of gradual substitution of Mn by Cr in FeCoNiAlMn (0.0 ≤ x ≤ 1.0) via the MA process to observe the effect of Cr3+ substitution on the structural, microstructural, and magnetic properties of the FeCoNiAlMn1–xCrx HEAP.

Results and Discussion

Phase Structure Analysis

Figure 1 represents the X-ray diffraction (XRD) pattern of milled equi-atomic FeCoNiAlMn HEAP after heating at 500 °C for 4 h. As a result, it shows that the HEAP formed a stable single-phase BCC solid solution structure corresponding to the (110) crystal plane at 2θ angles between 40 and 50°, which is consistent with Liu et al.’s26 analysis, and there is no phase transition in the alloy system during substitution since both the substituted elements Mn and Cr promote the BCC phase. The XRD peaks were observed to slightly shift toward the higher angle with the increasing Cr3+ contents in FeCoNiAlMn1–xCrx with the same stable BCC phase. The shifting of peaks may be associated with replacing the lower ionic radius of Cr3+ (0.61 Å) compared to Mn3+ (0.64 Å).25 However, the observed XRD pattern is consistent with previous reports for FeCoNiAlCr HEA prepared through arc melting observed in the BCC solid solution phase.24

Figure 1.

Figure 1

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XRD pattern of FeCoNiAlMn1–xCrx (x = 0, 0.2, 0.4, 0.6, 0.8, and 1 mole) HEA powder milled for 45 h and vacuum-heated at 500 °C for 4 h.

It was a major single BCC phase system, but it could be that a minute peak might have appeared due to different factors like milling time, temperature, etc. Similarly, the lattice parameters after substitution remained more or less the same, with no major changes being observed because the major phase remained the stable BCC one. However, a slight shift in the peak and peak broadening may probably cause a very negligible change in the calculated parameters.

From the XRD data, the inter-planar space, lattice parameter, crystallite size, and lattice strains of all the samples were calculated.

The inter-planar space and the lattice parameter “a” for the major BCC structure were calculated by Bragg’s eqs 1 and 2, respectively

graphic file with name ao3c01823_m001.jpg 1
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where “n” is the order of diffraction, which is usually taken as n = 1. “λ” is the wavelength of X-rays (here, Cu Kα X-rays were used, having a value of 1.5406 Å). “dhkl”represents the inter-crystalline planar distance with miller indices (hkl). “θ” is the diffraction angle.

The average crystallite size (D) was calculated from the most prominent diffraction peak of the (1 10) plane by using the Scherer’s formula given in eq 3.

graphic file with name ao3c01823_m003.jpg 3

where “k” is the constant having a value of 0.9. “θ” is the peak position. “λ” is the wavelength of the incident X-ray beam for Cu Kα radiations. “β” is full width at half-maximum. The lattice strain (ε) and the dislocation density (δ) developed during MA for milled and vacuum heated alloy powders are calculated through eqs 4 and 5, respectively.

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All the parametric values calculated for the MA HEAPs are represented in Table 1. It is true according to a relation since the dislocation density has an inverse relation with the crystallite size, as shown in eq 5.

Table 1. Structural Parametric Values of FeCoNiAlMn1–xCrx MA HEAP.

contents (x) VEC lattice parameter a (Å) crystallite size D (nm) lattice strain ε
0.0 7.40 2.897 13.631 0.139
0.2 6.13 2.894 11.466 0.296
0.4 6.12 2.891 13.265 0.223
0.6 6.06 2.856 13.262 0.259
0.8 6.03 2.858 13.186 0.297
1.0 7.20 2.857 12.982 0.446
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As seen from the parametric values represented in Table 1, no significant change was observed in the lattice constant “a” because of comparable atomic radii of Mn (r = 1.61 Å) and Cr (r = 1.66 Å). The values of lattice parameters for all the HEAPs after heating were very close to those of Fe and Cr.27 However, a significant change appeared in the crystallite size and lattice strains due to compositional variations as well as heating. The crystallite size is in the nano-range from 13.63 to 11.1 nm after heating. The decrease in crystallite size after heating might be due to the increase in the dislocation density; it can be related to eq 5. VEC representing the valence electron concentration by this theoretical phase formation of BCC or FCC solid solution phase is confirmed. Guo et al.36 also investigated the VEC influence on phase stability in a variety of solid solution-producing HEAs containing various alloying elements. According to the rule, BCC phases stabilize at lower VEC in solid solution HEAs; however, FCC phases stabilize at greater VEC. Both FCC and BCC phases exist in the intermediate VEC region. The FCC phase exists quantitatively at VEC ≥ 8, the BCC phase exists at VEC < 6.87, and a combination of both FCC and BCC phases exists at 6.87 ≤ VEC < 8.37 These parameter values before heating are not given because before heating the XRD peaks did not stand out well.

Scanning Electron Microscopy/Energy-Dispersive Spectroscopy Analysis

Particles shapes, sizes, and their distribution within the samples of FeCoNiAlMn1–xCrx (x = 0, 0.2, 0.4, 0.6, 0.8, and 1 mole) HEAP were analyzed by scanning electron microscopy (SEM). The images of each sample were taken with X2000 magnification at a 10 μm scale length as shown in Figure 2. It can be seen from the SEM images that the particles were uniformly distributed and homogenized with a wide range of sizes from ∼1 to 7 μm (particle size was calculated by a software ImageJ). However, most of the particles were below 3 μm, but clusters of large particles were also formed. The shape of the particles also varied from round or spherical to a polygonal shape.23 When Mn was replaced by Cr, the particles of the HEAP became small and stuck together with no voids observed. For all the HEAPs FeCoNiAlMn1–xCrx from x = 0.2 mole till x = 0.8 mole, all the particles showed a well-defined structure with voids; most of the particle sizes observed were <10 μm. However, some large particles were also observed in SEM images. For FeCoNiAlCr, all the particles stuck together and formed a very small particle size of almost 5 μm, which was observed with no voids but with a sponge-like structure.

Figure 2.

Figure 2

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SEM images of FeCoNiAlMn1–xCrx [(a) x = 0, (b) 0.2, (c) 0.4, (d) 0.6, (e) 0.8, and (f) 1 mole] MA HEAP milled for 45 h and vacuum-heated at 500 °C for 4 h.

For the elemental composition analysis of the MA- and vacuum-heated HEAPs, energy-dispersive spectroscopy (EDS) was performed. The EDS of each HEAP is as shown in Figure 3 and compositional analysis is given in adjacent Table 2. It is clear from the EDS spectrum peaks as well as the elemental table that all the elements were present in the alloy powders with no significant foreign element peak. Moreover, it can be observed from the scanned image of vacuum-heated powder samples that each element was more or less uniformly distributed throughout the matrix. However, the wt % of each element varied in different alloy powders.

Figure 3.

Figure 3

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EDX graphs of FeCoNiAlMn1–xCrx [(a) x = 0, (b) 0.2, (c) 0.4, (d) 0.6, (e) 0.8, and (f) 1 mole] MA HEAP milled for 45 h and vacuum-heated at 500 °C for 4 h.

Table 2. Atomic Percentage Composition of FeCoNiAlMn1–xCrx MA HEAP at 45 h and after Vacuum-Heating at 500 °C for 4 ha.

Elements (at. %) x = 0 x = 0.2 x = 0.4 x = 0.6 x = 0.8 x = 1
Al 17.90 15.22 19.78 21.76 18.50 18.90
Cr   7.31 5.59 5.37 13.24 13.41
Mn 20.47 22.40 12.30 8.79 4.78 22.83
Fe 20.08 18.84 19.42 18.78 20.52 23.37
Co 22.04 18.92 22.84 24.66 23 21.49
Ni 19.51 17.31 20.08 20.63 19.96 18.90
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a

There was no oxygen (O) peak observed in the above EDX spectra because MA was carried out in an inert atmosphere in the presence of argon.

Magnetic Properties’ Analysis

The magnetic properties of the FeCoNiAlMn and FeCoNiAlMn1–xCrx (x = 0, 0.2, 0.4, 0.6, 0.8, and 1 mole) HEAP vacuum-heated at 500 °C have been investigated by vibrating sample magnetometry. Figure 4 represents M-H loops of FeCoNiAlMn1–xCrx (x = 0, 0.2, 0.4, 0.6, 0.8, and 1 mole) measured at room temperature. All of the alloy powders easily magnetized up to their saturated state with low coercivity, representing soft magnetic behavior. Li et al.26 and Na et al.28 also studied the magnetization exhibiting ferromagnetic behavior in FeCoNiAlMn (x = 0 mole) and FeCoNiAlCr (x = 1 mole) HEA prepared through vacuum arc melting. Magnetic parameters obtained from hysteresis loop saturation magnetization (Ms) remanence (Mr) and coercivity (Hc) of FeCoNiAlMn1–xCrx (x = 0, 0.2, 0.4, 0.6, 0.8, and 1 mole) are given in Table 3. The dependence of saturation magnetization (Ms) and coercivity (Hc) on composition (x) are shown in Figure 5. The amount of atomic magnetic moments per unit volume, which determines a material’s Ms, is mostly influenced by its composition.27 The change in structure would have an impact on Ms once the required composition of a material was established. From the XRD analysis, it is observed that the phase microstructure for x = 0, 0.2, 0.4, 0.6, 0.8, and 1 mole remained the same BCC one. It is observed that Ms increases with Cr concentration up to x = 0.6 and then start decreasing with complete replacement of Mn with Cr, while coercivity decreased with x = 0.2; afterward it increased up to x = 1. However, all samples show soft magnetic behavior (maximum Hc = 192 Oe). The composition-dependent saturation magnetization could be explained by considering the magnetic ordering of Mn and Cr atoms as Mn and Cr are both paramagnetic atoms and in bulk form, and they act as antiferromagnetic elements with antiferromagnetic ordering in some cases. The small increase in saturation magnetization (Ms) with Cr-substitution was because Cr acted as a paramagnetic element with the matrix elements; nevertheless, with the complete replacement of Mn, the magnetic moment of Cr was anti-parallel to (Fe/Co/Ni) (i.e., anti-parallel magnetic coupling)31 such that the magnetization cancelled out in the Cr-containing HEAP,hence reducing the saturation magnetization. The BCC and FCC crystalline structures of HEAP FeCoNiAlMnCr coexist in 0.2 ≤ x ≤ 0.4 and after complete replacement of Cr, the structure again becomes a BCC one. FeCoNi has a high Ms of 149.65 emu/g because of ferromagnetic ordering. However, by adding nonmagnetic or paramagnetic elements such as Mn and Al, for example, FeCoNiAl has Ms of 101.77 emu/g and FeCoNiMn has Ms of 18.14 emu/g. Interestingly the saturation magnetization enhances in the equi-atomic FeCoNiAlMn alloy. However, Hc first decreases at x = 0.2 and then increases again up to x = 1. The coercivity decreases sharply by increasing the Cr concentration from x = 0 to x = 0.2 and then increases with complete Mn replacement with Cr. The coercivity is strongly related to particle size, strain, and dislocation density.29 The Hc is susceptible to different microstructures and lattice deformation. Magnetic domain wall movement and Hc are both impacted by the lattice distortion.30 The atomic radius of Cr is similar to that of Mn as represented in Table 1. Table 3 depicts Hc wrt x; among all, x = 0.4 lattice distortion is the least in MA powders before heating. This might be the reason for the lowest Hc for x = 0.4 and the maximum Ms after MA. As it can be seen from the XRD data and SEM results, the particle size, residual stress–strain, and dislocation density decrease in this range, which reflects that the coupling between ferromagnetic grains increases as the coercivity decreases. Nevertheless, after complete replacement of Cr that is at x = 1, the residual stress–strain increases as the coercivity increases. Nevertheless, our results suggest that all the MA HEAPs are promising candidates for soft magnetic applications.

Figure 4.

Figure 4

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M–H curve of the FeCoNiAlMn1–xCrx (x = 0, 0.2, 0.4, 0.6, 0.8, and 1 mole) HEAP milled for 45 h and vacuum-heated at 500 °C for 4 h.

Table 3. Saturation Magnetization (Ms), (Mr), and Hci (Oe) of the FeCoNiAlMn1–xCrx HEAP Milled for 45 h and Vacuum-Heated at 500 °C for 4 h.

sample (x mole) Ms (emu/g) Mr (emu/g) Hci (Oe)
0.0 62.92 4.06 178.21
0.2 64.60 3.31 130.52
0.4 68.15 3.16 132.02
0.6 68.91 3.08 151.48
0.8 64.63 4.84 187.51
1.0 51.91 5.18 192.01
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Figure 5.

Figure 5

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M–H curve of the FeCoNiAlMn1–xCrx (x = 0, 0.2, 0.4, 0.6, 0.8, and 1 mole) HEAP milled before and after vacuum heating.

Generally, the magnetic properties including Ms and Hc of a material depend on different factors. According to Wei et al.,27Ms is predominantly determined by the composition and atomic-level structures and is less responsive to microstructures such as grain size and shape. Unlike Ms, Hc is likely to be impurity- and subsequent heat treatment-sensitive.35 The movement of magnetic domain walls is affected by the lattice deformation induced by Mn and Cr, leading to changes in Hc. When the composition of MA HEAPs is varied by increasing the amount of Cr (with a magnetic moment of 3.05 μB) and decreasing the amount of Mn (with a magnetic moment of 5.17 μB), magnetic centers are generated in the bulk phase, causing fluctuations in Ms during substitution. Substituting Cr for Mn as an impurity and heating for crystallization also contribute to fluctuations in Hc.

Similarly, another reason might be that since coercivity depends on magnetic domains, grain boundaries, and also particle size, the variations in these factors ultimately cause variation in the coercivity. A smaller nano-metric microstructure enhances the magnetic properties of the HEAPs because exchange correlation increases as the number of magnetic moments increases on the surface; as particle size decreases, so the number of magnetic moments on the surface increases.

The results of many studies show that the magnetic properties of particles are strongly affected by magnetic anisotropy. Overall, magnetic properties are the equilibrium of magnetic anisotropies and interparticle interactions, for example, exchange and dipolar interactions. Therefore, in order to analyze the anisotropy factors, the M–H loops measured at room temperature were used to find the effective magnetic anisotropy theoretically by applying the law of approach to magnetic saturation also known as law of saturation (LAS).32−34

graphic file with name ao3c01823_m006.jpg

where M is the magnetization with respect to the applied field H and Ms is the saturation magnetization for H approaching infinity. The constant A is an inhomogeneous parameter, and the term A/H describes the influence of crystal defects, vacancies, lattice distortion, and local concentration fluctuations, which cause hindrance in the movement of magnetization vectors due to domain wall interactions with these factors. The second constant B is the magnetic anisotropy parameter, and the term B/H2 is concerned with magneto-crystalline anisotropy. The last term represents the spontaneous magnetization (χ is the magnetic susceptibility), whereas the spontaneous magnetization is connected with the Curie temperature. Since our measurements were at room temperature, which are well below the Curie temperature, this term is neglected. Through this LAS, Ms of the HEAPs were calculated theoretically.

Conclusions

In this study, FeCoNiAlMn1–xCrx (x = 0, 0.2, 0.4, 0.6, 0.8, and 1 mole) HEAP has been prepared by MA, and the effect of gradual substitution and heating on the phase structure, microstructure, and magnetic properties of the alloy has been analyzed. It has been observed that there is no phase transition; thus, obtaining the same BCC solid solution phase after gradual substitution during MA and the same single-phase microstructure was observed during substitution. However, only the crystallization of the alloy powder improved after heating and grain growth developed. The magnetic properties of both substituted and heated HEAPs after MA showed the same soft magnetic properties. But saturation magnetization and coercivity both showed fluctuations after substitution and heating. The reason for these fluctuations in magnetic properties was that saturation magnetization is dependent on composition, so the changes in composition caused saturation magnetization to fluctuate. However, coercivity is dependent on distortion that was induced during substitution, causing it fluctuate. So, the saturation magnetization of the MA alloyed powders is affected by compositional variations, while microstructural change, heating, and domain wall movement affected the coercivity during the substitution of Mn by Cr.

Experimental Methods

Synthesis of HEAPs

High-purity elemental powders of iron (Fe), cobalt (Co), nickel (Ni), aluminum (Al), and manganese (Mn) were used as raw materials for MA using the ball-milling method. These powders have purity >99.9% with initial particle sizes of about 150, 50, <50, 40–75, and <50 μm for each element, respectively. The elemental powders were mechanically alloyed using a PQ-N04 type planetary high energy ball mill in an inert atmosphere of Ar gas, and no oxidation occurred during the entire MA process. The total volume of the ball mill container was about 50 mL with 5 and 7 mm diameter stainless steel balls used as grinding media. The premixed powders were mechanically alloyed with a ball to powder weight ratio of 6:1 at 500 rpm milling speed for producing equi-atomic FeCoNiAlMn HEAP. First, only FeCoNiAlMn HEAP was prepared through MA, which lasted for 45 h. Afterward, a new milling process was conducted for each composition of FeCoNiAlMn1–xCrx with respective molar ratios (x = 0.2, 0.4, 0.6, 0.8, and 1) under the same conditions for 45 h. The ball mill container and its balls were washed with ethanol for about 30 min before starting a new milling process to remove impurities. The milling process consisted of a sequence of 25 min forward cycles, followed by a 2 min stop, a 25 min reverse cycle, and another 2 min stop. This complete cycle was repeated for 45 h to achieve continuous milling with minimum heat accumulation. To achieve perfect crystallization of the alloyed powders, FeCoNiAlMn1–xCrx (x = 0, 0.2, 0.4, 0.6, 0.8, and 1 mole) samples were heated to a high temperature of approximately 500 °C for 4 h in a horizontal vacuum quenching furnace (Model WZC 60) at a vacuum pressure of 1 × 10–3 pascal. The samples were heated under vacuum conditions and then cooled down to 250 °C in a vacuum cooling chamber. During the vacuum heat treatment process, the alloyed powders were placed in a ceramic crucible covered with a ceramic lid.

Characterizations of the Powder Alloy Samples

The phase structure of equi-atomic FeCoNiAlMn HEAP with gradual substitution of Mn by Cr in the form of FeCoNiAlMn1–xCrx (x = 0, 0.2, 0.4, 0.6, 0.8, and 1 mole) HEAP and following the MA was analyzed by PANalytical model X’pert PRO Origin X-ray diffractometer with Cu Kα X-ray radiation (λ = 1.54 Å). The 2θ scan has been done between the range of 10–70° with a scanning rate of 0.05° s–1 under a working voltage of 40 kV and current of 30 mA. The microstructure, particle size, and elemental composition of the alloyed powders were investigated through SEM (JSM-6490LV JEOL, Japan-2008). The magnetic property measurements for the as-synthesized HEAPs have been conducted using a Lakeshore Vibrating Sample Magnetometer 3 tesla at room temperature. Magnetization curves have been recorded for −10,000 to +10,000 Oe applied magnetic fields. Phase structure, microstructure, and magnetic properties of the alloy powders after vacuum heat treatment have also been studied and compared with milled HEAPs.

Acknowledgments

The authors extend their appreciation to the Deanship of Scientific Research at King Khalid University Abha 61421, Asir, Kingdom of Saudi Arabia, for funding this work through the Large Groups Project under grant number RGP.2/142/44. The authors would like to thank Princess Nourah bint Abdulrahman University Researchers Supporting Project number (PNURSP2023R9), Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia, for supporting this project.

The authors declare no competing financial interest.

References

  1. Yeh J. W.; Chen S. K.; Lin S. J.; Gan J. Y.; Chin T. S.; Shun T. T.; Tsau C. H.; Chang S. Y. Nanostructured high-entropy alloys with multiple principal elements: novel alloy design concepts and outcomes. Adv. Eng. Mater. 2004, 6, 299–303. 10.1002/adem.200300567. [DOI] [Google Scholar]
  2. Tong C. J.; Chen Y. L.; Yeh J. W.; Lin S. J.; Chen S. K.; Shun T. T.; Tsau C. H.; Chang S. Y. Microstructure characterization of Al x CoCrCuFeNi high-entropy alloy system with multiprincipal elements. Metall. Mater. Trans. A 2005, 36, 881–893. 10.1007/s11661-005-0283-0. [DOI] [Google Scholar]
  3. Miracle D. B.; Senkov O. N. A critical review of high entropy alloys and related concepts. Acta Mater. 2017, 122, 448–511. 10.1016/j.actamat.2016.08.081. [DOI] [Google Scholar]
  4. Praveen S.; Kim H. S. High-entropy alloys: potential candidates for high-temperature applications–an overview. Adv. Eng. Mater. 2018, 20, 1700645. 10.1002/adem.201700645. [DOI] [Google Scholar]
  5. Qiu Y.; Thomas S.; Gibson M. A.; Fraser H. L.; Birbilis N. Corrosion of high entropy alloys. npj Mater. Degrad. 2017, 1, 15. 10.1038/s41529-017-0009-y. [DOI] [Google Scholar]
  6. Sahlberg M.; Karlsson D.; Zlotea C.; Jansson U. Superior hydrogen storage in high entropy alloys. Sci. Rep. 2016, 6, 36770. 10.1038/srep36770. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Karati A.; Nagini M.; Ghosh S.; Shabadi R.; Pradeep K. G.; Mallik R. C.; Murty B. S.; Varadaraju U. V. Ti2NiCoSnSb-a new half-Heusler type high-entropy alloy showing simultaneous increase in Seebeck coefficient and electrical conductivity for thermoelectric applications. Sci. Rep. 2019, 9, 5331. 10.1038/s41598-019-41818-6. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Koželj P.; Vrtnik S.; Jelen A.; Jazbec S.; Jagličić Z.; Maiti S.; Feuerbacher M.; Steurer W.; Dolinšek J. Discovery of a superconducting high-entropy alloy. Phys. Rev. Lett. 2014, 113, 107001. 10.1103/physrevlett.113.107001. [DOI] [PubMed] [Google Scholar]
  9. Belyea D. D.; Lucas M. S.; Michel E.; Horwath J.; Miller C. W. Tunable magnetocaloric effect in transition metal alloys. Sci. Rep. 2015, 5, 15755. 10.1038/srep15755. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Gao M. C.; Miracle D. B.; Maurice D.; Yan X.; Zhang Y.; Hawk J. A. High-entropy functional materials. J. Mater. Res. 2018, 33, 3138–3155. 10.1557/jmr.2018.323. [DOI] [Google Scholar]
  11. Jiang L.; Lu Y.; Wu W.; Cao Z.; Li T. Microstructure and mechanical properties of a CoFeNi2V0. 5Nb0. 75 eutectic high entropy alloy in as-cast and heat-treated conditions. J. Mater. Sci. Technol. 2016, 32, 245–250. 10.1016/j.jmst.2015.08.006. [DOI] [Google Scholar]
  12. Karati A.; Guruvidyathri K.; Hariharan V. S.; Murty B. S. Thermal stability of AlCoFeMnNi high-entropy alloy. Scr. Mater. 2019, 162, 465–467. 10.1016/j.scriptamat.2018.12.017. [DOI] [Google Scholar]
  13. Suryanarayana C. Mechanical alloying and milling. Prog. Mater. Sci. 2001, 46, 1–184. 10.1016/s0079-6425(99)00010-9. [DOI] [Google Scholar]
  14. Chen Z.; Chen W.; Wu B.; Cao X.; Liu L.; Fu Z. Effects of Co and Ti on microstructure and mechanical behavior of Al0. 75FeNiCrCo high entropy alloy prepared by mechanical alloying and spark plasma sintering. Mater. Sci. Eng., A 2015, 648, 217–224. 10.1016/j.msea.2015.08.056. [DOI] [Google Scholar]
  15. Gómez-Esparza C. D.; Baldenebro-López F.; González-Rodelas L.; Baldenebro-López J.; Martínez-Sánchez R. Series of nanocrystalline NiCoAlFe (Cr, Cu, Mo, Ti) high-entropy alloys produced by mechanical alloying. Mater. Res. 2016, 19, 39–46. 10.1590/1980-5373-mr-2015-0668. [DOI] [Google Scholar]
  16. Zhang Y.; Zuo T.; Cheng Y.; Liaw P. K. High-entropy alloys with high saturation magnetization, electrical resistivity and malleability. Sci. Rep. 2013, 3, 1455. 10.1038/srep01455. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Li P.; Wang A.; Liu C. T. A ductile high entropy alloy with attractive magnetic properties. J. Alloys Compd. 2017, 694, 55–60. 10.1016/j.jallcom.2016.09.186. [DOI] [Google Scholar]
  18. Zuo T.; Gao M. C.; Ouyang L.; Yang X.; Cheng Y.; Feng R.; Chen S.; Liaw P. K.; Hawk J. A.; Zhang Y. Tailoring magnetic behavior of CoFeMnNiX (X= Al, Cr, Ga, and Sn) high entropy alloys by metal doping. Acta Mater. 2017, 130, 10–18. 10.1016/j.actamat.2017.03.013. [DOI] [Google Scholar]
  19. Kao Y. F.; Chen S. K.; Chen T. J.; Chu P. C.; Yeh J. W.; Lin S. J. Electrical, magnetic, and Hall properties of AlxCoCrFeNi high-entropy alloys. J. Alloys Compd. 2011, 509, 1607–1614. 10.1016/j.jallcom.2010.10.210. [DOI] [Google Scholar]
  20. Kao Y. F.; Lee T. D.; Chen S. K.; Chang Y. S. Electrochemical passive properties of AlxCoCrFeNi (x= 0, 0.25, 0.50, 1.00) alloys in sulfuric acids. Corros. Sci. 2010, 52, 1026–1034. 10.1016/j.corsci.2009.11.028. [DOI] [Google Scholar]
  21. Chou H. P.; Chang Y. S.; Chen S. K.; Yeh J. W. Microstructure, thermophysical and electrical properties in AlxCoCrFeNi (0≤x≤2) high-entropy alloys. Mater. Sci. Eng., B 2009, 163, 184–189. 10.1016/j.mseb.2009.05.024. [DOI] [Google Scholar]
  22. Huang S.; Li W.; Li X.; Schönecker S.; Bergqvist L.; Holmström E.; Varga L. K.; Vitos L. Mechanism of magnetic transition in FeCrCoNi-based high entropy alloys. Mater. Des. 2016, 103, 71–74. 10.1016/j.matdes.2016.04.053. [DOI] [Google Scholar]
  23. Yang C.; Zhang J.; Li M.; Liu X. Soft-magnetic high-entropy AlCoFeMnNi alloys with dual-phase microstructures induced by annealing. Acta Metall. Sin. 2020, 33, 1124–1134. 10.1007/s40195-020-01086-0. [DOI] [Google Scholar]
  24. Duan Y.; Wen X.; Zhang B.; Ma G.; Wang T. Optimizing the electromagnetic properties of the FeCoNiAlCrx high entropy alloy powders by composition adjustment and annealing treatment. J. Magn. Magn. Mater. 2020, 497, 165947. 10.1016/j.jmmm.2019.165947. [DOI] [Google Scholar]
  25. Shannon R. D. Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallogr., Sect. A: Cryst. Phys., Diffr., Theor. Gen. Crystallogr. 1976, 32, 751–767. 10.1107/s0567739476001551. [DOI] [Google Scholar]
  26. Li P.; Wang A.; Liu C. T. Composition dependence of structure, physical and mechanical properties of FeCoNi (MnAl) x high entropy alloys. Intermetallics 2017, 87, 21–26. 10.1016/j.intermet.2017.04.007. [DOI] [Google Scholar]
  27. Wei R.; Sun H.; Chen C.; Han Z.; Li F. Effect of cooling rate on the phase structure and magnetic properties of Fe26. 7Co28. 5Ni28. 5Si4. 6B8. 7P3 high entropy alloy. J. Magn. Magn. Mater. 2017, 435, 184–186. 10.1016/j.jmmm.2017.04.017. [DOI] [Google Scholar]
  28. Na S. M.; Yoo J. H.; Lambert P. K.; Jones N. J. Room-temperature ferromagnetic transitions and the temperature dependence of magnetic behaviors in FeCoNiCr-based high-entropy alloys. AIP Adv. 2018, 8, 056412. 10.1063/1.5007073. [DOI] [Google Scholar]
  29. Bittner F.; Freudenberger J.; Schultz L.; Woodcock T. G. The impact of dislocations on coercivity in L10-MnAl. J. Alloys Compd. 2017, 704, 528–536. 10.1016/j.jallcom.2017.02.028. [DOI] [Google Scholar]
  30. Han L.; Maccari F.; Souza Filho I. R.; Peter N. J.; Wei Y.; Gault B.; Gutfleisch O.; Li Z.; Raabe D. A mechanically strong and ductile soft magnet with extremely low coercivity. Nature 2022, 608, 310–316. 10.1038/s41586-022-04935-3. [DOI] [PMC free article] [PubMed] [Google Scholar]
  31. Jung C.; Kang K.; Marshal A.; Pradeep K. G.; Seol J. B.; Lee H. M.; Choi P. P. Effects of phase composition and elemental partitioning on soft magnetic properties of AlFeCoCrMn high entropy alloys. Acta Mater. 2019, 171, 31–39. 10.1016/j.actamat.2019.04.007. [DOI] [Google Scholar]
  32. Yi L.; Zhang T.; Zhang B.; Xu Y.; Piao H.; Pan L. Induced magnetic anisotropy of Ni42Co8Mn39Sn11 Heusler alloy under magnetic-field-annealing. J. Magn. Magn. Mater. 2020, 495, 165843. 10.1016/j.jmmm.2019.165843. [DOI] [Google Scholar]
  33. Zhang H.; Zeng D.; Liu Z. The law of approach to saturation in ferromagnets originating from the magnetocrystalline anisotropy. J. Magn. Magn. Mater. 2010, 322, 2375–2380. 10.1016/j.jmmm.2010.02.040. [DOI] [Google Scholar]
  34. Rafique M. Y.; Pan L. Q.; Javed Q. u. a.; Iqbal M. Z.; Qiu H. M.; Farooq M. H.; Guo Z. G.; Tanveer M. Growth of monodisperse nanospheres of MnFe2O4 with enhanced magnetic and optical properties. Chin. Phys. B 2013, 22, 107101. 10.1088/1674-1056/22/10/107101. [DOI] [Google Scholar]
  35. Chiriac H.; Tomut M.; Neagu M. Improving the magnetic properties of nanocrystalline Fe73. 5Cu1Nb3Si13. 5B9 by heat treatment of the melt. Nanostruct. Mater. 1999, 12, 851–854. 10.1016/s0965-9773(99)00250-0. [DOI] [Google Scholar]
  36. Ke G. Y.; Chen S. K.; Hsu T.; Yeh J. W. FCC and BCC equivalents in as-cast solid solutions of AlxCoyCrzCu0. 5FevNiw high-entropy alloys. Ann. Chim. 2006, 31, 669–684. 10.3166/acsm.31.669-684. [DOI] [Google Scholar]
  37. Jin X.; Marioni M.; Bono D.; Allen S. M.; O’handley R. C.; Hsu T. Y. Empirical mapping of Ni–Mn–Ga properties with composition and valence electron concentration. J. Appl. Phys. 2002, 91, 8222–8224. 10.1063/1.1453943. [DOI] [Google Scholar]

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