Effect Of Dy Addition Research Articles

Microstructure and magnetic properties of Dy-added Alnico alloys

Alnico permanent alloys are still irreplaceable and show great potential in high temperature applications considering their excellent thermal stability, while the market for Alnico alloys is limited by their low coercivity. Rare-earth addition has been shown to increase the coercivity of Alnico alloys. In this work, the effects of Dy-addition on the crystal structure, microstructure, spinodal decomposition phases and magnetic characteristics of Alnico alloys were systematically investigated. The results indicate that the Dy element forms Dy-rich precipitates and influences the morphology and composition of spinodal decomposition structure. The 0.3 wt% Dy addition improves the coercivity from 132 kA·m−1 for the Dy-free alloys to 141 kA·m−1 for the Dy-added alloys and slightly optimizes the thermal stability. The enhancement of coercivity is attributed to the refined and uniform spinodal decomposition structure by reducing the mismatch degree and coherency strain. However, the magnetic properties of the 0.6 wt% Dy added alloy decrease due to the damaged structure with excessive Dy-rich phases and more connected α1 phases. A method for improving coercivity and thermal stability is suggested.

Effects of Dy Addition on the Mechanical and Degradation Properties of Mg–2Zn–0.5Zr Alloy

As candidates for biomaterials, magnesium and its alloys have promising properties such as biodegradability and biocompatibility. However, their poor mechanical properties and rapid degradation rate limit clinical application; therefore, solving these issues is essential for practical application. Herein, different contents of dysprosium (Dy) (0, 0.5, 1, 1.5, 2, 3 mass%) are added to the Mg–2Zn–0.5Zr biomagnesium alloy to explore its effect on the mechanical and degradation properties. Assessments are conducted using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), immersion, and electrode chemical experiments. The results indicate that the addition of Dy significantly decreases the grain size, and the second phase is (Mg, Dy)7Zn3 with a body‐centered cubic structure. At a Dy content of 1.5 mass%, grain refinement and second‐phase strengthening result in the alloy having relatively good properties, with an ultimate tensile strength (UTS) = 150 ± 14 MPa, yield strength (YS) = 89 ± 3 MPa, and elongation (EL) = 9.2 ± 0.6%. The addition of Dy promotes the formation of a stable protective film and increases the electrode potential of the Mg matrix, resulting in a degradation rate of 0.89 ± 0.12 mm year−1. The results indicate that the alloy with 1.5 mass% Dy content is a promising candidate for using as a biodegradable material.

Effect of Dy addition on magnetocaloric effect in PrCo2 compound

The effect of Dy addition on the structure, magnetic and magnetocaloric properties of polycrystalline PrCo2 compound were investigated by x-ray diffraction (XRD) and magnetic measurements. The powder XRD patterns show that all the Pr1-xDyxCo2 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) samples are linear solid solutions with C15 cubic Laves phase and MgCu2-type structure. With the increases of Dy content, the lattice parameter decreases from 7.3090 Å for PrCo2 to 7.1914 Å for DyCo2, and the Curie temperature increases from 42 K (x = 0.0) to 151 K (x = 1.0). From the Arrott plots, the sample show the first order transition when 0.4 ≤ x ≤ 1.0. The magnetic entropy change of second-order PrCo2 compound is 10.7 J kg−1·K−1. And the magnetic entropy change of Pr0.6Dy0.4Co2 is the minimum of the whole system. After x ≥ 0.4, the magnetic entropy change value gradually increases, up to 10.4 J kg−1·K−1 for first-order DyCo2 compound. The RCP of these compounds was discussed.

Effect of Dy Addition on the Microstructure and Mechanical Property of Ti-Nb-Dy Alloys

The effects of adding rare-earth element Dy on the microstructure, hardness, and elastic modulus of Ti78−x Nb22Dyx (x=0.7, 2, and 5) alloys were investigated experimentally. The microstructure of Ti78−xNb22Dyx alloys consists of matrix (β phase and α″ martensite) and Dy-rich precipitates. The hardness can be increased with adding an appropriate amount of Dy. The elastic modulus decreases gradually with the increase of Dy fraction.

The Effects of Dy Addition on Microstructure and Mechanical Properties of the As-Cast Mg-5Al-3Ca-2Nd Alloys.

The microstructure of the as-cast Mg-5Al-3Ca-2Nd-xDy alloys consists of α-Mg matrix, (Mg, Al)2Ca eutectic phase, Al-Nd and Al-Dy intermetallic compounds. α-Mg matrix morphology was changed from dendritic to equiaxed with the increase Dy addition. And grain size was remarkably refined. As Dy content was increased, yield strength was improved due to the refined grains and the homogeneous distribution of Al-Dy phase.

Effect of Dy addition on microstructure and mechanical properties of Mg-4Y-3Nd-0.4Zr alloy

Minor Dy element was added into a Mg-4Y-3Nd-0.4Zr alloy, and its effects on the microstructure and the mechanical properties at elevated temperatures were investigated. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to observe the microstructures. The results indicated that the as-cast eutectic and isolated cuboid-shaped Mg-RE phases were Mg5RE and Mg3RE17, respectively, and distributed mainly along grain boundaries. After a solution treatment, the eutectic Mg5RE phases were dissolved into the matrix, whereas the Mg3RE17 compound still remained. After peak aging, fine Mg-RE phases were precipitated homogeneously within the matrix of the alloys containing Dy. Dy addition can result in a significant improvement in the tensile strength at both room and elevated temperatures, and a slight decrease in the elongation.

YDy<i><sub>x</sub></i>Ba<sub>2</sub>Cu<sub>3</sub>O<sub>7-δ</sub> Epitaxial Films Prepared by Chemical Solution Deposition

YBa2Cu3O7-δ (YBCO) coated conductors have wide-ranging potential in large scale applications, such as, superconducting maglev trains and superconducting electric cables, but low current carrying capability restrains the practical application of YBCO coated conductors at high temperatures and high magnetic fields. It is crucial to develop YBCO coated conductors with high flux pinning capability. In this paper, epitaxial, dense, smooth and crack-free YDyxBa2Cu3O7-δ (x = 0~0.5) films were prepared on a LaAlO3 (LAO) single crystal substrate via a fluorine-free polymer-assisted metal organic deposition (PA-MOD) method. The effects of Dy addition on the microstructure and superconducting character of YBCO films were investigated. The all films show a strong c-axis orientation and good texture in-plane and out of plane. The Dy addition to the YBCO film hardly affects the critical temperature of YBCO superconductor. The irreversibility fields of YBCO films can be improved with the Dy addition x = 0.5 compared to the pure YBCO film but decreased in the x = 0.3 sample.

Effect of Dy Addition on the Magnetic and Mechanical Properties of Sintered Nd–Fe–B Magnets Prepared by Double-Alloy Powder Mixed Method

Many new approaches have been successfully developed to reduce the Dy content, such as double alloy method, grain refinement and grain boundary diffusion processes [1, 2]. However, as for the mass production of sintered Nd-Fe-B magnets, these methods have some disadvantages in the cost of production. Sintered Nd-Fe-B magnets are very brittle, and easily crack during assembly and machine work and operation, which limit their applications. Many methods including grain boundary toughening and particle dispersion strengthening have been used to enhancing the mechanical properties of sintered Nd-Fe-B magnets to extend their applications. Double-alloy powder mixed method can modify the compositions and realize the microstructure regulation, and be used for mass production of sintered Nd-Fe-B magnets. In the present work, the effect of Dy addition on the magnetic and mechanical properties of sintered Nd-Fe-B magnets prepared by double-alloy powder mixed method was studied.

Thermal stability, magnetic and mechanical properties of Fe–Dy–B–Nb bulk metallic glasses with high glass-forming ability

The effects of Dy addition on the thermal stability, glass-forming ability (GFA), magnetic and mechanical properties of quaternary (Fe0.76−xDyxB0.24)96Nb4 (x = 0–0.07) bulk metallic glasses (BMGs) were investigated. Increasing Dy content from x = 0 to 0.05 extended the supercooled liquid region up to 112 K, allowing the fabrication by copper mold casting of BMGs rods with 5.5 mm in diameter. The high GFA was found to be related to the structure of primary crystalline phase. For the x = 0.05 alloy, the competitive formation process of the complex Fe23B6 and Dy2Fe14B phases enabled to obtain the largest GFA value. Moreover, the Fe–Dy–B–Nb BMGs exhibited good soft-magnetic properties, i.e., high saturation magnetization of 1.18–0.56 T and low coercive force of 1.9–21.6 A/m. In addition, the glassy alloy rods also showed high compressive fracture strengths of 4400–4150 MPa and high Vickers hardness of 1110–1090 kg/mm2.

The Origin of Coercivity Enhancement of Sintered NdFeB Magnets Prepared by Dy Addition

The effect of Dy addition on the microstructure and magnetic properties of the sintered NdFeB magnets was investigated. The results of the microstructure analysis showed that Dy-free and Dy-doped samples are composed of Nd₂Fe ₁₄B (P42/mnm) and a trace of Nd-rich phase. Dy addition reduces significantly the pole density factor of (004), (006) and (008) crystal faces as estimated by the Horta formula. Accordingly, the coercivity of the Dy-doped sample increases from 2038 kA·m?1 up to 2288 kA·m?1. The Hcj(T)/Ms(T) versus /Ms(T) (Kronmuller-plot) behavior shows that the nucleation is the dominating mechanism for the magnetization reversal in these two kinds of magnets, and two microstructural parameters of αk and Neff are obtained. The Kronmuller-Plot gives evidence for an increase of the αk responsible for an increase of the coercivity as the result of the increase of the magnetic field as the magnetic domain reversed.

Thermal stability and crystallization behavior of (Fe0.75 − xDyxB0.2Si0.05)96Nb4 (x = 0–0.07) bulk metallic glasses

Effects of Dy addition on the glass-forming ability (GFA), thermal stability, and crystallization behavior in (Fe0.75−xDyxB0.2Si0.05)96Nb4 (x=0–0.07) bulk metallic glasses (BMGs) were investigated. The thermal stability of the supercooled liquid was greatly improved by alloying with a small amount of Dy. The largest supercooled liquid region of 100K was achieved for the x=0.04 alloy, leading to the best GFA with a diameter of 4mm. The activation energy for the first crystallization peak increased with the addition of Dy. However, adding more Dy may also increase the frequency factor and change the primary precipitation phase from Fe23B6 phase into DyFe11Si and DyFe3 phases, decreasing the thermal stability of the supercooled liquid. The possible relation between GFA and thermal stability, as well as crystallization behavior is discussed.

Mechanical and functional properties of two-phase Ni53Mn22Co6Ga19 high-temperature shape memory alloy with the addition of Dy

The effects of Dy addition on microstructure, martensitic transformation, mechanical and shape memory properties of the two-phase Ni53Mn22Co6Ga19 high-temperature shape memory alloy were investigated. It is found that a small Dy addition results in the refinement of grain size, which can effectively improve the tensile ductility and strength of the two-phase Ni53Mn22Co6Ga19 alloy. However, a Dy(Ni,Mn)4Ga precipitate forms in the alloys with the Dy addition, and its amount increases with an increase in the Dy addition. This change causes the ductility of the alloys to decrease when the Dy addition is further increased to 0.3 at.%. The results further show that the changes in the martensitic transformation temperature of the studied alloys can be attributed to the combined effects of the tetragonality (c/a) and electron concentration (e/a) of martensite. Additionally, the shape memory effects of the alloys are closely related to the refinement of grain size and the alloy strength. In this study, the (Ni53Mn22Co6Ga19)99.8Dy0.2 alloy exhibits a variety of good properties, including a high martensitic transformation starting temperature of 385.7 °C, a tensile ductility of 10.3% and a shape memory effect of 2.8%.

Effect of Dy addition on mechanical and magnetic properties of Mn-rich Ni–Mn–Ga ferromagnetic shape memory alloys

The effects of partial substitution of rare earth Dy for Ga on the mechanical and magnetic properties of Mn-rich Ni50Mn29Ga21−xDyx (0≤x≤5) ferromagnetic shape memory alloys were investigated in detail. The results show that an appropriate amount of Dy addition significantly improves the mechanical properties of Ni–Mn–Ga alloy. With an increase in Dy content, the compressive strength enhances rapidly at first and then becomes stable when the Dy content is more than 1at.%. However, the compressive strain increases dramatically and reaches a maximum value with 1at.% Dy addition. Further increase in Dy content makes the compressive strain of the alloys decrease gradually. The mechanism of the improved mechanical properties is also discussed. Moreover, Dy doping changes the fracture type from intergranular fracture of Ni–Mn–Ga alloy to transgranular cleavage fracture of Ni–Mn–Ga–Dy alloys. The Curie temperature remains almost unchanged at low Dy content and subsequently decreases.

Soft-ferromagnetic bulk glassy alloys with large magnetostriction and high glass-forming ability

The effect of Dy addition on the glass-forming ability (GFA), magnetostriction as well as soft-magnetic properties and fracture strength in FeDyBSiNb glassy alloys was investigated. In addition to the increase of supercooled liquid region from 55 to 100 K, the addition of Dy is effective in approaching alloy to an eutectic point and increasing the saturation magnetostrction (λs). Accordingly, bulk glassy alloy (BGA) rods with diameters up to 4 mm were produced, which exhibit a large λs as high as 65×10-6. Besides, the BGA system exhibits superhigh fracture strength of 4000 MPa, combined with good soft-magnetic properties.

CYCLIC OXIDATION BEHAVIORS OF EB-PVD Dy DOPED β-NiAl COATINGS AT 1100°C

β- NiAl as a promising oxidation resistant coating material due to it high melting point and good oxidation resistant, however it reveals poor cyclic oxidation performance. In this paper, reactive element Dy doped β- NiAl coatings were prepared by electron beam physical vapor deposition (EB-PVD). Dy doping led to the grain refinement microstructure and Dy segregated mainly at grain boundaries. Cyclic oxidation behaviors of the coatings at 1100°C were investigated. The 0.05at.% Dy and 0.1at.% Dy doped coatings exhibited lower oxidation rate and better cyclic oxidation performance, as compared to the undoped coating. The effects of Dy addition on the morphologies and growth mechanism of the oxide scale were discussed.

Effect of Dy addition on the microstructure and martensitic transformation of a Ni-rich TiNi shape memory alloy

The effect of rare earth element Dy addition on the microstructure and martensitic transformation behavior of Ti 49.3Ni 50.7 shape memory alloy was investigated by optical microscope (OM), scanning electronic microscope (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results show that the microstructure of TiNiDy ternary alloy consists of Ti 2Ni phase, DyNi phase and the matrix. One-step martensitic transformation is observed in quenched TiNiDy ternary alloys, which is the same as that in quenched TiNi binary alloys. The martensitic transformation temperatures increase evidently with Dy addition, and the maximum increase of M s is about 110 °C.

Electrical Properties of Dy2O3-Doped BaTiO3

The effects of Dy addition on the electrical properties of BaTiO3 have been studied by analyzing equilibrium electrical conductivity as a function of temperature, oxygen partial pressure (Po2) and composition. In(Ba1-xDyx)TiO3+0.5x, the conductivity follows the -1/4th power dependence of Po2 at high oxygen activities, which supports the notion that cation vacancies are generated to compensate for Dy donors, and is nearly independent of Po2 where electron compensation prevails at a low Po2. The incorporation of “Dy3+” ion into Ti sites up to 2.0 mol% showed the typical acceptor-doped behavior of the Dy3+ ion. Curie temperature (Tc) was systematically decreased when the Dy3+ ion was incorporated into Ti sites.

Effect of Dy Addition on the Thermal Stability and Magnetic Properties of the Fe–Co–Nd–B Amorphous Alloys with Supercooled Liquid Region

The thermal stability, crystallized structure and magnetic properties of rapidly solidified Fe-Co-Nd-B amorphous alloys with Dy addition have been investigated. The supercooled liquid region (ΔT x ) of an amorphous Fe 66.5 Co 10 Nd 3.5 B 20 alloy increases from 40 to 45 K by the addition of 0.5 at%Dy. Both the amorphous alloys with and without Dy addition after optimum annealing are composed mainly of Fe 3 B, Nd 2 Fe 14 B and α-(Fe, Co) phases. By the addition of the small amount of Dy, the coercivity (i H c ) and maximum energy product (B H) max are greatly enhanced, though the remanence (B r ) slightly decreases, The B r , i H c and (B H) max after optimum annealing are 1.27 T, 187 kA/m and 86 kJ/m 3 , respectively, for the Fe 66.5 Co 10 Nd 3.5 B 20 alloy and 1.24 T, 263 kA/m and 92 kJ/m 3 , respectively, for the Fe 66.5 Co 9.5 Nd 3.5 Dy 0.5 B 20 alloy.