Correlation between hereditary structures and properties of an Fe<Subscript>50</Subscript>Cr<Subscript>15</Subscript>Mo<Subscript>14</Subscript>C<Subscript>15</Subscript>B<Subscript>6</Subscript> bulk-amorphous alloy in the solid and liquid states

An attempt is made to find the effect of a hereditary structure on the physicochemical and structural properties of a solid and liquid Fe₅₀Cr₁₅Mo₁₄C₁₅B₆ bulk-amorphous alloy in order to evaluate the possibility of using a precursor, i.e., a solid metal that has a genetic relation to the liquid phase, as an the initial metal of a heat involved in the formation of an amorphous structure. The structural state of the melt is estimated from the temperature dependence of the structural parameters, density, and surface tension with allowance for the validation criterion of the approximation of experimental points R ².     

Influence of heat treatment on the efficiency of impact fragmentation of amorphous alloy Fe<Subscript>73.5</Subscript>Cu<Subscript>1</Subscript>Nb<Subscript>3</Subscript>Si<Subscript>13.5</Subscript>B<Subscript>9</Subscript> ribbons

The mechanism of impact fracture of soft magnetic amorphous alloy Fe_73.5Cu₁Nb₃Si_13.5B₉ ribbons in a disintegrator after heat treatment at a temperature from the range 300–700°C and the fractional composition of the formed powder are studied. The temperature ranges of a change in the mechanism of ribbon fracture are determined. The particle size distribution is shown to change weakly within the revealed temperature ranges.     

Corrosion Behavior of Fe<Subscript>41</Subscript>Co<Subscript>7</Subscript>Cr<Subscript>15</Subscript>Mo<Subscript>14</Subscript>C<Subscript>15</Subscript>B<Subscript>6</Subscript>Y<Subscript>2</Subscript> Bulk Metallic Glass in Sulfuric Acid Solutions

An Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂ bulk metallic glass with a diameter of 5 mm was prepared with the copper-mold-casting method. The corrosion resistance of this amorphous steel in sulfuric-acid solutions was determined by electrochemical measurements. The passive film formed on the surface of the alloy after immersion in the 0.5-mol/l H₂SO₄ solution for 1 week was analyzed by X-ray photoelectron spectroscopy (XPS). Electrochemical measurements show that the corrosion resistance of the amorphous steel in the 1 mol/l-H₂SO₄ solution is superior to a stainless steel (SUS 321), and is almost the same as Ti6Al4V, which shows that the amorphous steel has an excellent corrosion resistance in sulfuric-acid solutions. As the concentration of the sulfuric-acid solutions increases from 0.5 mol/l to 4 mol/l, the corrosion resistance of the amorphous steel decreases. The XPS result reveals that a bilayer structure of protective film formed on the surface of the amorphous steel in a H₂SO₄ solution. The compositions of the inner part of the film are MoO₂, Cr₂O₃, CoO, and FeO, and those of the outer film are MoO₃, Cr(OH)₃, Co(OH)₂, and Fe(OH)₃.     

[(Fe<Subscript>0.5</Subscript>Co<Subscript>0.5</Subscript>)<Subscript>0.75</Subscript>B<Subscript>0.20</Subscript>Si<Subscript>0.05</Subscript>]<Subscript>96</Subscript>Nb<Subscript>4</Subscript> Metallic Glasses with Small Cu Additions

Recently, (Fe-Co)-B-Si-Nb bulk metallic glasses (BMGs) were produced. Such BMGs exhibit high glass-forming ability (GFA) as well as good mechanical and magnetic properties. These alloys combine the advantages of functional and structural materials. The soft magnetic properties can be enhanced by nanocrystallization. To force the nanocrystallization, small content of Cu was added to the starting composition. In this article, {[(Fe_0.5Co_0.5)_0.75Si_0.05B_0.20]_0.96Nb_0.04}_100–x Cu _x glassy alloys (x = 1, 2, and 3) were chosen for investigation. The GFA and the thermal stability of these alloys were evaluated. The effects of crystallization during heat-treatment processes on the phase evolution and the magnetic properties, including M _s , H _c , and T _c , in these alloys were investigated. The phase analyses were done with the help of the X-ray diffraction patterns recorded in situ by using the synchrotron radiation in transmission configuration.     

Phase transitions in the magnetic superconductor (Dy<Subscript>0.8</Subscript>Y<Subscript>0.2</Subscript>)Rh<Subscript>4</Subscript>B<Subscript>4</Subscript>

A new (Dy_0.8Y_0.2)Rh₄B₄ superconductor (the superconducting transition temperature is T _c ≈ 5.5 K), which has an inherent magnetic subsystem whose properties are determined by the crystal structure of the superconductor, is synthesized at a high pressure (∼8 GPa) and t ≈ 1800°. The magnetic sublattice of the (Dy_0.8Y_0.2)Rh₄B₄ compound is found to substantially affect its superconducting properties and, in a number of cases, to lead to their anomalous variations, namely, to the absence of the traditional Meissner effect and an anomalously abrupt increase in magnetic induction B _k2 (upper critical field) upon a transition of the magnetic subsystem into the antiferromagnetic state. Upon cooling from 250 to 1.6 K, the (Dy_0.8Y_0.2)Rh₄B₄ compound undergoes a number of phase transformations, namely, a paramagnet-ferrimagnet transition at a Curie temperature T _C ≈ 30 K, a superconducting transition at T _c ≈ 5.5 K against the background of a ferrimagnetic order, and a ferrimagnet-antiferromagnet transition (the Neel temperature is T _N ≈ 2.8 K) in the retained superconducting state.     

Deformation and fracture of a composite material based on a high-strength maraging steel covered with a melt-quenched Co<Subscript>69</Subscript>Fe<Subscript>4</Subscript>Cr<Subscript>4</Subscript>Si<Subscript>12</Subscript>B<Subscript>11</Subscript> alloy layer

Multifractal analysis is used to study the deformation and fracture of a promising composite material consisting of a wire base made of K17N9M14 maraging steel covered with a surface layer made from a Co₆₉Fe₄Cr₄Si₁₂B₁₁ amorphous alloy. As compared to its components, this material has a substantially better set of the mechanical properties.     

Effect of Planar Flow Melt Spinning Parameters on Ribbon Formation in Soft Magnetic Fe<Subscript>68.5</Subscript>Si<Subscript>18.5</Subscript>B<Subscript>9</Subscript>Nb<Subscript>3</Subscript>Cu<Subscript>1</Subscript> Alloy

The effect of planar flow melt spinning (PFMS) parameters on the continuity, surface quality, and structure of 10-mm-wide Fe_68.5Si_18.5B₉Nb₃Cu₁ ribbons has been investigated. The change in shape and stability of the melt puddle as a function of the processing parameter was studied using a high-speed imaging system and was correlated to ribbon formation. A window of process parameters for obtaining continuous ribbons with good surface quality has been evaluated. It has been observed that thinner ribbons are found to be more continuous because of higher ductility. The higher melt temperature leads to the formation of crystalline phase in as-spun ribbons, and this deteriorates the soft magnetic properties on annealing. The experimental results are corroborated with the numerical estimates, which suggest that the critical thickness for amorphous phase formation decreases with increasing initial melt temperature.     

Effect of the liquid phase on the formation of orthorhombic boride during the crystallization of Fe<Subscript>82</Subscript>B<Subscript>18</Subscript> amorphous ribbons

Amorphous Fe₈₂B₁₈ ribbons prepared by melt quenching from different temperatures have been studied during step-by-step heating. Depending on the quenching temperature, the crystallization of the ribbons was shown to occur via different mechanisms, namely, with and without the formation of the orthorhombic Fe₃B^orth boride. This is related to different structural states of the melt used for the preparation of the rapidly quenched ribbons. The appearance of the orthorhombic Fe₃B^orth boride is preceded by the crystallization of the amorphous component with the formation of the Fe₃B^tet boride having a distorted body-centered tetragonal lattice.     

Reduction of Fe<Subscript>2</Subscript>MoO<Subscript>4</Subscript> by hydrogen gas

In the present work, the reduction kinetics of iron molybdate (Fe₂MoO₄) by hydrogen gas was investigated by thermogravimetric analyses (TGA). Both isothermal and nonisothermal experiments were conducted. By using fine particles, very shallow powder bed, and high hydrogen flow rate, the study could be focused on the chemical reaction. The activation energy obtained from the isothermal experiments was found to be 173.5 kJ/mol, which was in reasonable agreement with the value of 158.3 kJ/mol obtained from the nonisothermal experiments. The reduction product was found to be an intermetallic compound, Fe₂Mo, of microcrystalline structure.     

Structure and mechanical properties of iron subjected to surface severe plastic deformation by friction: I. Structure formation

Depth-sensing indentation is used to study the effect of grain refinement to submicro- and nanograins on the mechanical properties (hardness, plasticity, Young’s modulus) of armco iron subjected to severe plastic deformation by attrition in argon. In contrast to fcc metals, where the hardness increases and the plasticity decreases as the grain size decreases to 20 nm, the hardness of bcc iron decreases from 5.8 to 3.7 GPa and plasticity δ _A increases from 0.82 to 0.87 as the grain size decreases from 50 to 20 nm.     

Effect of alloying additions on the structure and mechanical properties of Fe<Subscript>3</Subscript>Al -1C intermetallic alloy

Effect of titanium and nickel on the structure and properties of Fe₃Al intermetallic alloy containing about 1.0wt.% C have been investigated. The composition of the alloying element was substituted for Iron. The alloys were prepared by melting commercial grade raw materials iron, aluminum, titanium or nickel in air induction furnace with flux cover (AIMFC). Further these ingots were refined by electroslag refining (ESR) process. These ingots could be successfully hot-worked using conventional hot-forging and hot-rolling techniques. The hot-worked material was sound and free from cracks. ESR hot-rolled alloys were examined using optical microscopy, X-ray diffraction (XRD), scanning electron micrograph (SEM) to understand the microstructure of these alloys. The electron probe micro analysis (EPMA) studies were carried out to determine the matrix and precipitate compositions and to identify the phases present in the alloys. The base alloy and the alloy containing Ni exhibited a two-phase microstructure of Fe₃AlC_0.5 precipitates in Fe₃Al matrix. The alloy containing Ti exhibits three-phase microstructure, the additional phase being TiC precipitate. Ti addition resulted in no improvement in strength at room temperature and at 873 K whereas Ni addition has resulted in greater improvement in strength at room temperature and at 873 K and also improved the creep life significantly from 66 hrs to 111 hrs.     

Fabrication and characterizations of new glassy Co<Subscript>71</Subscript>Ti<Subscript>24</Subscript>B<Subscript>5</Subscript> alloy powders and subsequent hot pressing into a fully dense bulk glass

A single glassy phase of Co₇₁Ti₂₄B₅ alloy has been synthesized by high-energy ball milling the elemental powders at room temperature, using the mechanical alloying method. The synthetic glassy powder obtained after 130 ks of ball milling exhibits good soft magnetic properties with a polarization magnetization and coercivity values of 1.01 T and 2.86 kA/m, respectively. This ternary glassy alloy in which its glass transition temperature (T _g ) lies at a rather high temperature (805 K) crystallizes at 868 K through a single sharp exothermic peak with an enthalpy change of crystallization (ΔH _x ) of −3.28 kJ/mol. The supercooled liquid region before crystallization, ΔT _x of the synthesized glassy powders shows a large value (63 K) for a ternary system. The reduced glass transition temperature (ratio between T _g and liquidus temperatures, T _l (T _g /T _l )) was found to be 0.55. The end product of the glassy powder (130 ks) was compacted in an argon gas atmosphere at 835 K with a pressure of 780 MPa, using the hot-pressing technique. The consolidated sample is fully dense (∼99.5 pct) and maintains its chemically homogeneous glassy structure. The measured polarization magnetization and coercivity values of as-consolidated powders are measured and found to be 0.96 T and 2.92 kA/m, respectively. The Vickers microhardness of the bulk glassy Co₇₁Ti₂₄B₅ sample is measured and found to be in the range between 7.32 and 7.46 GPa.     

Electrochemical Behavior of an Amorphous and Nanocrystalline Fe<Subscript>79</Subscript>P<Subscript>13</Subscript>Si<Subscript>5</Subscript>V<Subscript>3</Subscript> Alloy in a Damp SO<Subscript>2</Subscript>-Contaminated Atmosphere

The electrochemical behavior of amorphous and nanocrystalline soft magnetic Fe₇₉P₁₃Si₅V₃ alloy in a 0.1 M Na₂SO₄ solution has been studied. Mössbauer studies show that the electrochemical characteristics of the alloy are comparable with those of an Finemet Fe₇₇Si₁₃B₇Nb_2.1Cu_0.9 alloy, whereas the studied alloy is inexpensive and can be prepared using natural alloy ferrophosphorus containing vanadium and silicon.     

Experimental Investigation and Thermodynamic Modeling of the B<Subscript>2</Subscript>O<Subscript>3</Subscript>-FeO-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-Nd<Subscript>2</Subscript>O<Subscript>3</Subscript> System for Recycling of NdFeB Magnet Scrap

NdFeB magnet scrap is an alternative source of neodymium that could have a significantly lower impact on the environment than current mining and extraction processes. Neodymium can be readily oxidized in the presence of oxygen, which makes it easy to recover neodymium in oxide form. Thermochemical data and phase diagrams for neodymium oxide containing systems is, however, very limited. Thermodynamic modeling of the B₂O₃-FeO-Fe₂O₃-Nd₂O₃ system was hence performed to obtain accurate phase diagrams and thermochemical properties of the system. Key phase diagram experiments were also carried out for the FeO-Nd₂O₃ system in saturation with iron to improve the accuracy of the present modeling. The modified quasichemical model was used to describe the Gibbs energy of the liquid oxide phase. The Gibbs energy functions of the liquid phase and the solids were optimized to reproduce all available and reliable phase diagram data, and thermochemical properties of the system. Finally the optimized database was applied to calculate conditions for selective oxidation of neodymium from NdFeB magnet waste.     

Orientation Relationship Between Magnetic Domains and Twins in Ni<Subscript>52</Subscript>Fe<Subscript>17</Subscript>Ga<Subscript>27</Subscript>Co<Subscript>4</Subscript> Magnetic Shape Memory Alloy

The orientation relationship between magnetic domain and twins in the directional solidified Ni₅₂Fe₁₇Ga₂₇Co₄ magnetic shape memory alloy was analyzed by electron backscatter diffraction and magnetic force microscopy. The twin interface plane was determined to be \( \{ \bar{1}10\} \) plates. The magnetic domains walls with a misorientation about 5 deg belong to low angle boundaries. According to the orientation relationship between twins and magnetic domains, the intersection angle on the observed surface can be estimated.