Ferromagnetic element microalloying and clustering effects in high Bs Fe-based amorphous alloys

Fe_(83)(Co_x,Ni_y)(B_(11)Si_2P_3C_1)_(1-x,y/17)(x,y=1–3)amorphous alloys with high saturation magnetic flux density(B_s)and excellent soft-magnetic properties were developed and then the microalloying and clustering effects were explored.The microalloying of Co and Ni improves the B_sfrom 1.65 T to 1.67–1.72 T and 1.66–1.68 T,respectively.The Ni-doped alloys exhibit better soft-magnetic properties,containing a low coercivity(H_c) of about 5.0 A/m and a high Effective permeability(μ_e)of(8–10)×10~3,whereas the microalloying of Co leads to a deteriorative H_c of 5.0–13.0 A/m and a μ_eof(5–8)×10~3.Moreover,microalloying of Ni can increase the ductile-brittle transition(DBT)temperature of the ribbons,while a totally opposite effect is found in the Co-doped alloys.The formation of dense α-Fe(Co,Ni)clusters during annealing process is used to explain the distinct effects of Co and Ni microalloying on the magnetic properties and bending toughness.     

Role of alloying elements in microstructures of beta titanium alloys with carbon additions

Abstract

The effect of 0.2 wt-%C on the microstructure of beta titanium alloys Ti-15X(Fe, Cr, Mn, Mo, Ni, Co, Cu, and V) has been studied using scanning and transmission electron microscopy. It has been found that coarse eutectic TiC_x tends to be formed in beta titanium alloys containing Fe, Cr, Mo, and Mn, and relatively finer homogeneous TiC_x is formed in alloys containing V, Ta, Co, Ni, or Cu. The volume fraction of TiC_x in alloys containing Cu, Co, and Ni is much less than that in other beta titanium alloys. The oxygen content of the matrix is lower than that of Ti₂C in Cr or alloys containing Mn and higher than that of Ti₂C in alloys containing Mo or Ni. These observations are discussed in terms of the role of phase diagrams and the effect of atomic radius of alloying elements on the dimension of interstitial sites in the host alloy and the sublattice of TiC_x.     

Magnetic, Electrical and Thermodynamic Properties of UCuT x Al11−x Alloys Where T = Mn, Fe and x=4 and 5

The structure, magnetic, electrical, and thermodynamic properties of UCuT _x Al_11?x alloys, where T = Mn or Fe and x=4 or 5 are presented. The behavior of the Fe alloys is ferromagnetic-like with the Curie points amounting to 180 and 230 K, and the saturation magnetic moments under magnetic field of 5 T equal to 4.75 and 6.02 μ_B/f.u., respectively, whereas under a magnetic field of about 34 T the magnetic moments amount to 6.9 and 9.0 μ_B/f.u. for the alloys with x=4 and 5, respectively. The Curie points are reflected in the temperature dependence of the specific heat in which the anomalies are found at 180–200 and 230 K for alloys with x=4 and 5, respectively, however, it shows no reflection in the temperature dependence of the electrical resistivity. The field dependence of the magnetization at T=1.9 K for both compounds exhibits considerable hysteresis. There is a pronounced difference between ZFC and FC magnetization in its temperature dependence below the Curie point for materials with x=4 and 5. The Mn alloys exhibit ferrimagnetic-like character for which, supposedly, the interplay of the uranium and manganize sublattices is responsible. Magnetic transitions are determined at T _N =300 (x=4) and 380 K (x=5). However, those anomalies do not find confirmation in the temperature dependence of the specific heat and the electrical resistivity. Magnetic moments determined at T=1.9 K and in a magnetic field of 5 T are very low and in both cases amount to about 0.35 μ_B/f.u. and these values are slightly higher in a magnetic field of 34 T reaching a value of about 1.5 μ_B/f.u. Also for the Mn alloys the clear difference between ZFC and FC magnetization in its temperature dependence below the Curie point is observed.     

Magnetic properties of Ni–Co doped barium strontium hexaferrite

A series of Ni–Co substituted barium strontium hexaferrite materials, Ba_0.5Sr_0.5Ni _x Co _x Fe_12–2x O₁₉ (x = 0.0, 0.2, 0.4, 0.6, 0.8 mol%) was synthesized by the sol–gel method. X-ray diffraction analysis has shown that the Ni–Co substitutions maintain in a single hexagonal magnetoplumbite phase. The room temperature magnetic properties and the cation site preferences of Ni–Co substituted ferrite were investigated by VSM. Substitutions led to decrease in coercivity while saturation magnetization remains the almost same. It indicates that the saturation magnetization (52.81–59.8 Am²/kg) and coercivity (69.83–804.97 Oe) of barium strontium hexaferrite samples can be varied over a very wide range by an appropriate amount of Ni–Co doping contents.     

The excellent soft magnetic properties and corrosion behaviour of nanocrystalline FePCCu alloys

The effects of the addition of Cu on the crystallisation behaviour, soft magnetic properties, and corrosion behaviour of Fe_84-xP₉C₇Cu_x (x = 0–1.15) alloys were investigated. The experimental results demonstrate that the glass-forming ability of this alloy was improved and the soft magnetic properties of the alloy system were enhanced by proper Cu addition. FePCCu nanocrystalline alloys with a dispersed α-Fe phase were obtained by appropriately annealing the melt-spun ribbons at 693 K for 2 min. The Fe_83.25P₉C₇Cu_0.75 nanocrystalline alloy exhibited a high saturation magnetic flux density, B _s , of 1.64 T; a low coercivity, H _c , of 3.9 A/m; and a high effective permeability, μ _e , of 21,000 at 1 kHz. These characteristics are superior to corresponding properties of FePC alloys. Furthermore, the corrosion resistance of this nanocrystalline alloy increases when elevating the annealing temperature and was confirmed to be improved with respect to the corresponding amorphous alloy. These results indicate that this alloy is a promising soft magnetic material.     

Study of Electronic Structure,Magnetism, and Half-Metallicity of New Heusler Compounds CsTmO<Subscript>2</Subscript> (Tm = Fe,Co, Ni,and Cu)

The density functional calculations were performed using the full-potential linearized augmented plane wave (FPLAPW) method for new Heusler alloys CsTmO₂ (Tm = Fe, Co, Ni, and Cu). All compounds were stable in FM AlCu₂Mn-type structure. Results revealed that these alloys can be experimentally synthesized according to the calculated cohesive and formation energies. CsTmO₂ (Tm = Fe, Co, Ni, and Cu) alloys in AlCu₂Mn-type and CuHg₂Ti-type structures were half-metallic ferromagnets. The origin of half-metallicity in CsNiO₂ alloy was also discussed. The total magnetic moment of CsTmO₂ (Tm = Fe, Co, Ni, and Cu) alloys in both structures were 3 μ_B per formula unit and obeyed the Slater-Pauling rule (M_tot =?22 ? Z_tot). The relationship between the magnetism and half-metallicity of all compounds and the lattice constants was also studied. The half-metallic character in combined alloys CsTmO₂ (Tm = Fe, Co, Ni, and Cu) improved in comparison with Heusler alloys including transition metals which indicated that they may be good candidates for practical applications in spintronics.     

Composition and phase structure dependence of mechanical and magnetic properties for AlCoCuFeNix high entropy alloys

In this study, the effects of composition and phase constitution on the mechanical properties and magnetic performance of AlCoCuFeNi_x (x = 0.5, 0.8, 1.0, 1.5, 2.0, 3.0 in molar ratio) high entropy alloys (HEAs) were investigated. The results show that Ni element could lead to the evolution from face centered cubic (FCC), body centered cubic (BCC) and ordered BCC coexisting phase structure to a single FCC phase. The change of phase constitution enhances the plasticity but reduces the hardness and strength. One of the interesting points is the excellent soft magnetic properties of AlCoCuFeNi_x HEAs. Soft magnetic performance is dependent on composition and phase transition. AlCoCuFeNi_1.5 alloy, achieving a better balance of mechanical and magnetic properties, could be applied as structure materials and soft magnetic materials (SMMs). High Curie temperature (>900 K) and strong phase stability below 1350 K of AlCoCuFeNi_0.5 alloy confirm its practicability in a high-temperature environment. Atomic size difference (δ) is utilized as the critical parameter to explain the lattice strain and phase transformation induced by Ni addition.     

Study of Electronic,Mechanical, Magnetic,and Optical Properties of Mg<Subscript>0.75</Subscript>TM<Subscript>0.25</Subscript>S/Se (TM = Fe,Co, Ni): A First Principle Approach

A systematic study of the magnetism, mechanical, and optical behaviors of Mg_0.75TM_0.25S/Se (TM = Fe, Co, Ni) ordered alloys was conducted using the full-potential linearized augmented plane wave plus local orbital method. The ferromagnetic (FM) and antiferromagnetic (AFM) ground state energy differences and enthalpy of formation scrutinized their dynamical stability in the FM state. The elastic parameters decided their mechanical stability, ductile behavior, and partial ionic and covalent characters. Moreover, the calculated band structures and density of states revealed the type and origin of magnetism in terms of exchange splitting energies and exchange constants. The Fe- and Ni-doped MgS/Se alloys exhibited half metallic ferromagnetic (HMF) characteristics, while the Co-doped MgS/Se alloy depicted ferromagnetic semiconducting characters. A reduction in the magnetic moments of the transition metals was observed compared with their free space value, which is due to strong p-d hybridization. Furthermore, the optical spectrum showed the maximum light absorbed in the visible and in the UV region of the electromagnetic spectrum, which makes them potential candidates for optoelectronic and spintronic device applications.     

Magnetization reversal and tunable exchange bias behavior in Mn-substituted NiCr<Subscript>2</Subscript>O<Subscript>4</Subscript>

Single phase samples of Ni(Cr_1?xMn _x )₂O₄ (x = 0–0.50) were synthesized by using sol–gel route. Investigation of structural, magnetic, exchange bias and magnetization reversal properties was carried out in the bulk samples of Ni(Cr_1?xMn _x )₂O₄. Rietveld refinement of the X-ray diffraction patterns recorded at room temperature reveals the tetragonal structure for x = 0 sample with I4₁/amd space group and cubic structure for x ≥ 0.05 samples with \( {\text{Fd}\bar{3}\text{m}} \) space group. Magnetization measurements show that all samples exhibit ferrimagnetic behavior, and the transition temperature (T_C) is found to increase from 73 K for x = 0 to 138 K for x = 0.50. Mn substitution induces magnetization reversal behavior especially for 30 at% of Mn in NiCr₂O₄ system with a magnetic compensation temperature of 45 K. This magnetization reversal is explained in terms of different site occupation of Mn ions and the different temperature dependence of the magnetic moments of different sublattices. Study of exchange bias behavior in x = 0.10 and 0.30 samples reveals that they exhibit negative and tunable positive and negative exchange bias behavior, respectively. The magnitudes of maximum exchange bias field of these samples are found to be 640 and 5306 Oe, respectively. Exchange bias in x = 0.10 sample originates from the anisotropic exchange interaction between the ferrimagnetic and the antiferromagnetic components of magnetic moment. The tunable exchange bias behavior in x = 0.30 sample is explained in terms of change in domination of one sublattice moment over the other as the temperature is varied.     

Impact of Mn Substitution at Ru Site in?RuSr2(Eu1.4Ce0.6)Cu2O10?�� Magneto-Superconductor

We report the effect of Mn ion substitution on the structural, superconducting and magnetic properties of polycrystalline Ru_1?x Mn _x Sr₂(Eu_1.4Ce_0.6)Cu₂O_10??? system with x=0.0 to 0.50. All the samples crystallizes with tetragonal structure in I4/mmm space group. RuSr₂(Eu_1.4Ce_0.6)Cu₂O_10??? (EuRu-1222) is a reported magneto-superconductor with magnetic ordering at 100 K and superconductivity occurs at ?40 K. The exact nature of Ru spin magnetic ordering is still being debated and no conclusion has been reached yet. Here, we found the superconducting transition temperature T _c=15 K from the dc magnetization measurements for undoped sample. It is observed that the superconducting transition temperature decreases with the Mn doping at Ru site. DC magnetic susceptibility measurements exhibited ferromagnetic like transition for all the synthesized samples. It was also observed that the net magnetic moment decreases gradually with Mn doping, though not monotonically. It seems that doping of Mn in EuRu-1222 at Ru site enhance the AFM ordering of Ru spins and suppress the FM component. Our results point out possible coupling between superconductivity and magnetism.     

Reversible structural relaxation of amorphous Ni70TM5Si10B15 (TM = V,Cr, Mn,Fe, Co,Ni) alloys

The structural relaxation of amorphous Ni₇TM₅Si₁₀B₁₅ (TM = V, Cr, Mn, Fe, Co, Ni) alloy was investigated by the electrical resistance measurement under isochronal annealing. The reference Ni₇₅Si₁₀B₁₅ alloy showed no reversible changes in electrical resistance. All alloys other than TM = Ni exhibited a reversible change which is peculiar to the chemical short-range ordering. Only in TM = Cr alloy was the reversible part predominantly observed after pre-annealing, and in other alloys the irreversible change was also seen. The degree of reversible change below 623 K was in the order Fe > V > Cr > Co > Mn. This origin is discussed on the basis of Ni-TM correlation, which is considered to play an important role in ordering, and TM-metalloid correlation, which is considered to hinder the formation of an ordered phase.     

The effect of Ni additions on the oxidation behaviour of Co–Re–Cr high-temperature alloys

Abstract

The present study focused on the influence of Ni on the microstructure and oxidation behaviour of Co–Re–Cr-based alloys. Alloys with three different Ni contents were tested in laboratory air at 800–1100 °C. A refinement and a reduction of the σ phase volume fraction as well as a change in the matrix microstructure were observed. Thermogravimetric measurements showed that the alloys with higher Ni contents possess a better oxidation resistance when exposed to higher temperatures. All alloys suffered from continuous mass loss during oxidation at 800 °C due to the formation of porous oxides scales, consisting of Co₃O₄, Co(Ni)O and Ni-doped CoCr₂O₄, which allow the evaporation of Re-oxides. At 900–1100 °C, only the alloy with 25 at. % Ni showed parabolic oxidation kinetics after a short period of transient oxidation. This is a result of the fast formation of a protective Cr₂O₃ layer. It was also found that exposure to air at 1000 °C leads to a phase transformation of the bulk material; an oxidation-induced formation of fine hexagonal close-packed (hcp) grains was observed near the oxide scales. It is supposed that the improved oxidation resistance of Ni-containing Co–Re–Cr alloys is a result of enhanced Cr diffusion caused by the Ni addition. The extensive formation of the fcc phase in the alloy matrix had a detrimental effect on the oxidation behaviour of the Ni-containing Co–Re–Cr-based alloys.     

On the effect of cobalt doping on thermoelastic martensitic transformations in ferromagnetic Heusler Ni50 − x Co x Mn29Ga21 magnetically controlled shape memory alloys

The phase composition, structure, magnetic and thermoelastic martensitic transformations, and physical properties (magnetic susceptibility, magnetization, electric resistivity) in multicomponent magnetic Ni_{50 ? x} Co _x Mn₂₉Ga₂₁ alloys (with a Co content of x = 0, 1, 2, 3, and 10 at %) exhibiting a magnetically controlled shape memory effect are studied. The critical temperatures of the magnetic transitions and thermoelastic martensitic transformations are determined. It is shown that the studied alloys in the austenitic state are substitutional solid solutions based on a quasi-ternary L2₁ superstructure (Ni, Co)₅₀Mn₂₉Ga₂₁.     

Structural and Magnetic Properties of Transition Metal-Adsorbed MoS<Subscript>2</Subscript> Monolayer

The electronic and magnetic properties of transition metal (TM) atoms (TM = Co, Cu, Mn Fe, and Ni) adsorbed on a MoS₂ monolayer are investigated by density functional theory (DFT). Magnetism appears in the case of Co, Mn, and Fe. Among the three magnetic cases, the Co-adsorbed system has the most stable structure. Therefore, we further study the interaction in the two-Co-adsorbed system. Our results show that the interaction between the two Co atoms is always ferromagnetic (FM) and the p–d hybridization mechanism results in such ferromagnetic states. However, the FM interaction is obviously suppressed by increasing the Co–Co distance, which could be well explained by the Zener–Ruderman–Kittel–Kasuya–Yosida (RKKY) theory. Moreover, similar magnetic behavior is observed in the two-Mn-adsorbed system and a longrange FM state is shown. Such interesting phenomena suggest promising applications of TM-adsorbed MoS₂ monolayer in the future.     

Influence of head-tip morphology on contact properties for microconnector of Ni–Co alloy

To examine experimentally the influence of head-tip morphology on electrical and mechanical properties at the contact with a phosphor bronze, cantilever-type microconnectors of Ni–Co alloys were prepared by an electroplating technique. Here, the mol fraction y of Co in the Ni–Co alloy is 0.178, 0.204, 0.233 and 0.299. Among these alloys, the Vickers hardness is H _V = 510, 518, 525 and 478 for y = 0.178, 0.204, 0.233 and 0.299, respectively. Since the Vickers hardness is the maximum for y = 0.233, the Ni–0.233Co alloy may indicate the best wear-resistance. The loading and unloading manipulations were repeated to measure electrical resistance at the mechanical contact between the Ni–0.233Co microconnector and the phosphor bronze up to 10³ times. The repetitive measurement was conducted for microconnectors with thickness of 45 μm and head-tip curvature radii of r = 5, 25, 50 and 200 μm. Even at the initial repetition, the reliable electrical contact is actualized for r = 5 μm but not for r = 25–200 μm. The experimental result was quantitatively analyzed using a mechanical model. The analysis provides that the impression depth z of the head-tip into the phosphor bronze at the contact is mostly inversely proportional to r for r ≥ 5 μm. When r is measured in mm, the proportionality coefficient is 6 × 10^?7 mm². As a consequence, the most reliable electrical contact of the Ni–Co microconnector with r = 5 μm is ascribable to the largest impression depth of the head-tip into the phosphor bronze.     

Microstructure and martensitic transformation and mechanical properties of cast Ni rich NiTiCo shape memory alloys

Abstract

The influence of Co additions on the microstructure, second phase precipitates, phase transformation and mechanical properties of cast Ni_51?xTi₄₉Co_x (x?=?0, 0·5, 1·5 and 4 at-%) shape memory alloys was investigated. At the expense of Ni, Co added to NiTi alloy significantly increases the martensitic transformation temperature. The matrix phase in the microstructure of Ni₅₁Ti₄₉Co₀ alloy is the austenite phase (B2) in addition to martensite phase (B19′) and precipitates of NiTi intermetallic compounds. However, the parent phase in the other three alloys, Ni_50·5Ti₄₉Co_0·5, Ni_49·5Ti₄₉Co_1·5 and Ni₄₇Ti₄₉Co₄, is martensite. Ti₂Ni phase was found in the microstructures of the all investigated alloys; however, Ni₃Ti₂ phase precipitated only in the NiTi alloy with 0 at-%Co. The volume fraction of Ti₂Ni phase decreased by the additions of 0·5 and 1·5 at-%Co, while it is slightly increased with 4 at-%Co. The hardness value of NiTi alloy is affected by Co additions.     

A new resource-saving,low chromium and low nickel duplex stainless steel 15Cr–xAl–2Ni–yMn

A new family of resource-saving, low Cr and low Ni duplex stainless steels, with compositions of 15Cr–xAl–2Ni–yMn (x = 1.2–2.8, y = 8–12, wt.%) has been developed by examining the effect of Al and Mn on microstructure, mechanical property and corrosion property. The results show that 15Cr–1.2Al–2.0Ni–8Mn and 15Cr–2.0Al–2.0Ni–10Mn alloys have a balanced ferrite–austenite relation and that 15Cr–2.8Al–2.0Ni–12Mn alloy has a primary ferrite phase structure. The ferrite volume fraction increases with the solution treatment temperature and Al content while decreases with Mn content. No precipitate was found after solution-treated at 750 °C for 30 min. 15Cr–1.2Al–2.0Ni–8Mn alloy has a strong strain hardening effect, and 15Cr–2.0Al–2.0Ni–10Mn alloy has a good TRIP effect. Both of the 15Cr–1.2Al–2.0Ni–8Mn and 15Cr–2.0Al–2.0Ni–10Mn alloys have excellent impact toughness at low temperature with the impact energy higher than 125 J at −40 °C. The pitting corrosions always occur in austenite phase. Among the designed alloys, 15Cr–1.2Al–2.0Ni–8Mn and 15Cr–2.0Al–2.0Ni–10Mn are found to be excellent alloys with a proper phase proportion and a better combination of superior mechanical property and good pitting corrosion resistance.     

Correlation of microstructure and magnetic properties in Cu–Co–Ni alloys

The present study concerns correlation of microstructure and magnetic properties of nanocrystalline binary 50Cu–50Co and ternary 50Cu–25Co–25Ni (wt%) alloys prepared by ball milling and subsequent isothermal annealing of the ball milled alloys. High resolution transmission electron microscopic (HR-TEM) investigation has shown deformation-induced microstructural features. Field emission scanning electron microscopy (FE-SEM) has revealed a distinct change in morphology of as-milled CuCoNi alloys after annealing. Differential scanning calorimetric (DSC) and X-ray diffraction (XRD) analysis have revealed that annealing of the CuCoNi alloy above 350 °C results into precipitation of nanocrystalline Co (fcc) in the CuNi matrix by spinodal decomposition. It is also demonstrated that isothermal annealing of the ball milled alloys in the temperature range between 350 and 650 °C significantly influence the magnetic properties, e.g. coercivity (H_c), remanence (M_r) and magnetic saturation (M_s) due to annihilation of defects such as stacking and twin fault along with dissolution and/or precipitation of magnetic phases in the Cu-rich matrix.     

Nanostructured electrode materials for Ni-MH x batteries prepared by mechanical alloying

Nanocrystalline TiFe- and Mg₂Ni-type alloys were prepared by mechanical alloying followed by annealing. The structure and electrochemical properties of these materials were studied. The properties of hydrogen host materials can be modified substantially by alloying to obtain the desired storage characteristics. It was found that the respective replacement of Fe in TiFe by Ni and Mn improved not only the discharge capacity but also the cycle life of these electrodes. On the other hand, a partial substitution of Mg by Mn in Mg_2?x M _x Ni alloy leads to an increase in discharge capacity, at room temperature. Furthermore, the effect of the nickel and graphite coating on the structure of the nanocrystalline alloys and the electrodes characteristics were investigated. In Mg₂Ni-type alloy mechanical coating with graphite effectively reduced the degradation rate of the studied electrode materials.     

Synthesis of Fe–Co alloy and cobalt–magnetite composites doped with Nd3+ by using iron disproportionation

Iron–cobalt alloy and cobalt–magnetite composites doped with Nd³⁺ (Co _x Fe_1?x /Co _y Fe_1?y Nd _z Fe_2?z O₄) in which the Fe alloy has either a bcc or a fcc structure and the oxide is a spinel phase, have been synthesized by using the disproportionation of Fe(OH)₂ and the reduction of Co(II) by Fe⁰ in a concentrated KOH solution. Powder X-ray diffraction, scanning electron microscope and vibrating sample magnetometer were employed to characterize the crystallite sizes, structure, morphology and magnetic properties of the composites. And the effect of the Co(II)/Fe(II) ratio (0 ≤ Co/Fe ≤ 1), concentration of KOH, reaction time and substitution Fe³⁺ ions by Nd³⁺ ions on structure, magnetic properties of the composites were investigated. From the perspective of thermodynamics, we explain the postulated mechanism of the disproportionation reaction.