Sm2Fe17 Alloy Research Articles

Effect of heat treatment on the structure and magnetic properties of Sm-Fe alloys obtained by mechanical alloying

The effect of heat treatment on the structure and magnetic properties of Sm-Fe alloys obtained by mechanical alloying was investigated. The crystallization temperature of Sm2Fe17, an amorphous alloy obtained by mechanical alloying, was determined using differential scanning calorimetry. Based on these results, various samples were annealed at different isothermal holding temperatures, and those with the best magnetic properties were found. Experimental studies show that decreasing the isothermal holding temperature from 750 °C to 630 °C increases magnetic characteristics nearly four times. The saturation magnetization, romance and coercivity of the Sm2Fe17 powder were 121 emu/g, 28.5 emu/g and 800 Oe, respectively.

Optimization of Nitriding Regimes for Sm2Fe17 Alloy Powder

Currently, the most actively developing area in the field of permanent magnets is development of those based on compounds of rare-earth metals with transition metals. This is due to their unique magnetic properties that surpass those for ferrite and lithium magnets by several factors and makes them irreplaceable with utilization in aero and automobile building, robot technology, computers, etc. Among all of the compounds of iron with rare-earth elements, the greatest iron content and, consequently, highest saturation magnetization applies to R2Fe17 compounds (R is rare-earth element). Regimes are studied for nitriding alloy powders (Sm0.9Zr0.1)Fe17 and Sm2(Fe0.9Co0.1)17 in a nitrogen atmosphere with excess pressure of 15 kPa and temperature of 440–450°C. Dependences are established for phase composition and main magnetic parameters of nitriding regime.

The Pretreatment of Reduction-Diffusion Prepared Sm–Fe Alloy Using CaH2 Before Nitriding Process

The Pretreatment of Reduction-Diffusion Prepared Sm–Fe Alloy Using CaH2 Before Nitriding Process

Preparing Sm2Fe17Cx compound by high-energy ball-milling Sm-Fe alloy in heptane followed by annealing, re-milling and re-annealing

In this paper, we present a new preparation method for Sm2Fe17Cx compound based on solid-liquid reaction. High-energy ball-milled in heptane for 8h, Sm25Fe75 alloy containing SmFe2, SmFe3 and Sm2Fe17 phases disproportionates into SmH2+δ, α-Fe, Fe3C and graphite. H and C atoms come from heptane. Annealed to 850°C under vacuum, SmH2+δ decomposes and Sm-C, Sm2Fe14C, α-Fe are formed. Re-milling for 1.5h in argon and re-annealing at 600°C for 15min promotes the transformation of partial Sm2Fe14C to Sm2Fe17Cx (x: 0.3–1.5) and the formation of nanoscale microstructure. Due to the intergrain exchange coupling between magnetically hard Sm2Fe17Cx and soft Sm2Fe14C/α-Fe, the product behaves like magnet with single magnetically hard phase. Maximum coercivity of 4.4kOe is obtained. Shorter ball-milling time (6h) results in the insufficiency of α-Fe and Fe3C, limiting the formation of Sm2Fe14C and the transformation of Sm2Fe14C to Sm2Fe17Cx. Longer ball-milling time (10h) results in excess of α-Fe in the final product. Both cases reduce the ratio of magnetically hard phase to soft one in the nanocomposite magnet, resulting in the decrease of coercivity.

Effect of boron additions on phase formation and magnetic properties of TbCu7-type melt spun SmFe ribbons

Melt spun ribbons of a series of SmFe12Bx (x=0.0, 0.5, 0.75, 1.0, 1.25, and 1.5) have been prepared by the melt spinning technique. Sm–Fe–B melt spun ribbons with single phase TbCu7-type structure were prepared from the SmFe12Bx (x=0.5, 0.75, and 1.0) alloys at the surface velocity around 40m/s. The addition of boron not only inhibits the appearance of soft magnetic phase α-Fe, but also enhances the ability of amorphous formation for melt spun Sm–Fe ribbons. The concentration of boron atoms, however, exceeds the limit of the solubility (x>1.0) of Sm–Fe alloys, which does not impede the appearance of α-Fe but accelerates the formation of metastable phase Sm2Fe23B3 that is unfavorable to their magnetic properties. Moreover, it is found that the addition of boron whose concentration is 0.0≤x≤0.75 can stabilize the metastable TbCu7-type structure because of the increase of the lattice parameter ratio c/a. The magnetic properties of as-annealed SmFe12B1.0 melt spun ribbons with an energy product of 2.19MGOe, a coercivity of 2.36kOe and a remanence of 4.8kGs have been achieved. The microstructural characteristics of as-annealed melt spun SmFe12 and SmFe12B1.0 ribbons have been discussed as well. The following sequence of the hyperfine field H(6l)<H(3g)<H(2e) and the isomer shift δ(3g)<δ(6l)<δ(2e) is obtained by the analysis of 57Fe Mossbauer spectra. As the boron content is added gradually, the hyperfine fields of 3g and 6l sites increase slightly due to the competition of the positive electron polarization and the negative polarization. However, the value of H(2e) is almost constant.

Preparation of Sm2Fe17 alloy by reduction–diffusion process

Sm2Fe17 alloy is the intermediate material for the preparation of Sm2Fe17N x (x ≈ 3); thus, the synthesis of pure Sm2Fe17 mother alloy is the key to obtaining high-performance Sm2Fe17N x . Reduction–diffusion (R–D) is a cost-effective method. In this study, the R–D process of synthesizing Sm2Fe17 was analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and X-ray fluorescence (XRF). Furthermore, the influences of the tightness of compacted reactants, the compensation amount of Sm2O3, and the particle size of Fe on the formation of Sm2Fe17 were discussed from the aspects of the three raw materials. The results show that Sm reduced from Sm2O3 reacts with Fe particles to form intermetallic compound Sm2Fe17 directly in the R–D reaction process of preparing Sm2Fe17; the generation of Sm and its migration to the surface of Fe particles control the reaction rate; a proper tightness of compacted reactants is necessary for ensuring the purity of Sm2Fe17 product; pure Sm2Fe17 can be obtained when the compensation of Sm2O3 is 33 % of the stoichiometry; and the sufficiency of the reaction improves with the decrease in the size of Fe powders under the same reaction condition.

Structural transformation and magnetic properties of Sm–Fe alloys with V doping

A systematical investigation was carried out on structure and magnetic properties in SmFe9−x V x (x = 0.4, 0.8, 1.2) compounds prepared by a single-roller quenching method. The high cool-down rate leads to metastable TbCu7 phase in the parent compound, which gradually transforms into equilibrium ThMn12 structure with V-doping content increasing. The Curie temperature increases from 470 to 590 K with V doping, which is consistent with the phase transformation. Surprisingly, simultaneous increase in both coercivity and remanence is resulted by V doping, reaching the highest value of 685 kA·m−1 and 44.8 × 10−3 A·m2·g−1 in x = 1.2 compound, respectively. This phenomenon can be explained by the combination of phase transformation and intergranular exchange coupling through δM-H plots.

Nitrogenation effect of Sm2Fe17 alloys prepared by strip casting technique

Sm2Fe17 alloys prepared by strip casting technique can be directly nitrided to prepare interstitial Sm2Fe17NX compounds without pre-crushing. A phenomenon of spontaneous pulverization in the Sm2Fe17 strips induced by nitrogenation is found. This kind of pulverization may arise from the inter-granular fracture along the Sm-rich grain boundary phase as well as trans-granular fracture of Sm2Fe17 primary phase. Anisotropic Sm2Fe17N2.85 powders with a remanence (Br) of 14.1 kGs, a coercive force (iHc) of 12.1 kOe, and a maximum energy product ((BH)max) of 33 MGOe can be prepared using the nitrided strips.

Study on Preparation of the Precursor of Sm&lt;sub&gt;2&lt;/sub&gt;Fe&lt;sub&gt;17&lt;/sub&gt; Alloy by Oxalate Co-Precipitation

In the oxalate system, some factors of pH values, reactant concentration, feeding method and reaction temperature affecting the grain size and morphology of the precursor of Sm2Fe17 alloy by co-precipitation were investigated. By means of comprehensive experimental and XRD and SEM analysis, the optimum conditions for preparing the precursor of Sm2Fe17 alloy by co-precipitation were obtained and it laid a sound foundation for the subsequent preparation of high-performance magnetic material.

Preparation of Sm&lt;sub&gt;2&lt;/sub&gt;Fe&lt;sub&gt;17&lt;/sub&gt; Columnar Grains Ribbons by Rapid Quenching

The ingot of Sm-Fe alloy was prepared by vacuum melting. After a process of coarse crushing, it was made into Sm-Fe ribbons by melt-spinning. By analysis of XRD and SEM, it was confirmed that the ribbons composed of fine Sm2Fe17 columnar grains with almost the same orientation can be obtained under the condition of 5~7m/s surface rotating velocity of Cu wheel, suitable nozzle size, injection pressure, temperature and composition of the Sm-Fe melt to regulate cooling rate and crystallization. The achievement of the ribbons lays a foundation for preparing anisotropic Sm2Fe17Nx magnetic powders by rapid quenching.

Self-organized nanorods in disproportionated Sm2Fe17 and NdFe10.5Mo1.5 alloys

Self-organized rod-like disproportionation microstructures were obtained in Sm2Fe17 alloy by modifying the hydrogenation disproportionation desorption recombination (HDDR) process. The SmH2 nanorods are uniformly embedded in a Fe matrix. All the SmH2 are oriented along the same direction, and show a certain orientation relationship with the Fe matrix. Similar morphology was also observed in the disproportionated products of the NdFe10.5Mo1.5 alloy. However, for both Sm2Fe17 and NdFe10.5Mo1.5 alloys, no crystallographic orientation relationship is found between the recombined grains and the corresponding disproportionated products, and there is no crystal texture in the HDDR treated magnetic powders.

J044041 鉄系薄膜の磁歪の改善([J04404]知的材料・構造システム(4))

Sm-Fe alloy thin films were prepared by DC magnetron sputtering process. The atomic ratio of Sm-Fe film from SmFe2 4 to SmFe2 0 was varied with the Ar gas pressure from 0.2 to 1 Pa. Decreasing of an Ar gas pressure as sputtering gas raised the magnetostriction of SmFe2 2 film. The giant magnetostriction is found in the Sm-Fe and Pd-Fe on the thick sheet of titanium. The thickness enlargement of substrate enhances the magnetstriction value at each magnetic field.

Synthesis of Giant Magnetostrictive Iron-rich Sm-Fe Alloy by Unidirectional Solidification in Microgravity

Synthesis of Giant Magnetostrictive Iron-rich Sm-Fe Alloy by Unidirectional Solidification in Microgravity

ChemInform Abstract: Improvement in the Cast Structure of Sm2Fe17 Alloys by Niobium Additions.

Abstract A technique for producing Sm2Fe7 from cast ingots without the presence of free iron has been developed which involves the addition of between 4 and 5% Nb to the melt. The free iron is thereby replaced by paramagnetic NbFe2. A nitriding procedure for this material in N2 gas to produce Sm2Fe17N3−δ with δ≈0.3 is described.

환원-확산법에 의한 Sm-Fe 합금분말 제조시 Sm2O3첨가량의 영향

To produce alloy powders with only SmFe single phase by reduction-diffusion (R-D) method, the effect of excess samarium oxide on the preparation of Sm-Fe alloy powder during R-D heat treatment was studied. The quantity of samarium oxide was varied from 5% to 50% whereas iron and calcium were taken 0% and 200% in excess of chemical equivalent, respectively. The pellet type mixture of samarium, iron powders and calcium granulars was subjected to heat treatment at 1100 for 5 hours. The R-D treated pellet was moved into deionized water and agitated to separate Sm-Fe alloy powders. After washing them in deionized water several times, the powders were washed with acetic acid to remove the undesired reaction products such as CaO. By these washing and acid cleaning treatment, only 0.03 wt% calcium remained in Sm-Fe alloy powders. It was also confirmed that the content of unreacted -Fe in SmFe matrix gradually decreased as the percentage of samarium oxide is increased. However, there was no significant change above 40% excess samarium oxide.

High coercivity Sm–Fe melt-spun ribbon

The results of an investigation of the synthesis of the Sm5Fe17 phase and its magnetic properties are presented. It was found that the Sm5Fe17 phase can be produced by the annealing of a Sm–Fe melt-spun ribbon with a Sm content of 15–27.5 at. %. The coercivity of the annealed melt-spun ribbon was highly dependent on both the annealing temperature and the Sm content of the Sm–Fe alloy. The Sm22.5Fe77.5 melt-spun ribbon annealed at 973 K consisted of the Sm5Fe17 phase and exhibited a large coercivity of over 40 kOe.

The kinetics of hydrogen-induced diffusive phase transformations in Sm&lt;sub align=right&gt;2Fe&lt;sub align=right&gt;17 alloys

The kinetics of hydrogen-induced direct and reverse phase transformations in Sm2Fe17 alloys have been investigated. It is shown that a decrease in temperature leads to a significant slowdown of the direct and reverse phase transformations' evolution. It has been specified that these phase transformations proceed by the mechanism of nucleation and growth. Isothermal kinetic diagrams of both direct and reverse phase transformations have been plotted and the activation energy values for these hydrogen-induced phase transformations have been defined. It is shown that phase transformation kinetics in the interval of the temperatures under study is controlled by a mutual diffusion of the alloy's components.

Synthesis and magnetic properties of Sm 5Fe 17 hard magnetic phase

It was found that Sm–Fe alloys with the Sm5Fe17 phase can be obtained by annealing of the amorphous melt-spun ribbon. Unlike the Nd5Fe17 phase, the hard magnetic Sm5Fe17 phase was found to be the metastable phase. Thermomagnetic studies revealed the Curie temperature of the Sm5Fe17 phase to be 550 K. The resultant annealed melt-spun ribbon exhibited a large coercivity value of 2.9 MA m−1 at room temperature and 5.0 MA m−1 at 4 K.

Fabrication and magnetic properties of Sm3(Fe, Ti)29N x /α-Fe dual-phase nanocomposite permanent magnetic material

Sm3(Fe,Ti)29Nx/α-Fe dual-phase nanometer magnetic material was fabricated through rapid solidification, crystallization and nitridation of Sm-Fe (Ti) alloy. The effect of combination of rapid solidification and Ti alloy addition on the phase formation and microstructure of the Sm-Fe alloy is investigated in this paper. The microstructure of amorphous phase and dual-phase nano-grain crystals before and after crystallization annealing were observed using a high-resolution transmission electron microscope (HREM). The dual-phase nano-grains after annealing were compacted together with a clear interface with the direct exchange-coupling mechanism. Different annealing processes were used to examine the melt-spun alloy. Comparison of the images of SEM showed that annealing at 750 °C for 10 min was most suitable to get homogeneous and nano-grains. No obvious kink was detected in the second quadrant of the hysteresis loop like a single hard magnet, and strong exchange coupling was found between hard magnets and soft magnets.

Preparation of isotropic Sm 2Fe 17N x magnetic powders and their bonded magnets

The isotropic Sm 2Fe 17N x magnetic powders were prepared by Hydrogenation-Disproportion-Desorption-Recombination (HDDR) process. The phase and microstructure evolutionary process of Sm-Fe alloy during the solidification, homogenization, HDDR and nitration processes were investigated by means of XRD, SEM, EDX and AFM. The results show that the homogeneous Sm 2Fe 17 alloy was successfully obtained and the impurity phases and residual stress were well removed by heated at 1050 °C for 24 h. When heated at 800 °C for 1h in H 2 of 0.1 MPa, the alloy turns into SmH x and α-Fe with plenty of nanocrystals. After vacuumized at 800 °C for 2 h the alloy recombines into Sm 2Fe 17 with a crystal grain size of about 85 nm. The lattice constant of the alloy increases and the expanding of the crystal cell reaches 6.28% after nitrified at 500 °C for 5 h. The magnetic property of isotropic bonded Sm 2Fe 17N x magnets is B r = 0.6704 T, H cj = 1015 kA·m −1, ( BH) max = 73.7 kJ·m −3 with a density of 6.04 g·cm −3.