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[en] Through this work we study the influence of the thickness of boron paste in the growth of Fe2B boride layer during the paste boriding thermochemical treatment applied on AISI 1045 steel. Different thickness of boron paste over the material surface with constant temperature and time show the variability of the diffusion coefficient of boron in Fe2B phase depending, basically, on the boron potential at the external surface of the substrate. The mobility of boron in the formed phase is determined by the balance mass equation that considers the concentration profiles in the corresponding interphases layer-substrate, the thermodynamic equilibrium in the growth of the iron boride layer and the experimental results obtained during the process
[en] Study of surface treatment of steels by boron trifluoride with sand to obtain a hard Fe2B coating
[fr]Mise au point d'une methode de traitement de surface des aciers par le trifluorure de bore en presence de sable pour obtenir une couche de Fe2B sur les aciers
[en] The anisotropy of the Nd_2Fe_1_4B powder is originated during the creation of a fine Fe2B lamellar structure in the disproportionation step. The aspect ratio (A/R) of Fe2B structure increased from 3.37 ± 1.5 to 6.69 ± 3.2 during phase decomposition for 0 ∼ 60 min at 820 ℃ (P_H_2 = 10 kPa). The Fe_2B having high A/R ratio recombined Nd_2Fe_1_4B, which is close to the single domain, and the magnetic properties are also improved with increasing A/R ratio.
[en] A ferrous compound material was synthesized in this work, by the air auto-combustion of mixtures of powdered ferroboron and ferrotitanium, compacted under pressures of 79 and 93 MPa and preheated to a temperature of about 1000oC. The synthesized compounds were characterized by XRD analysis, and macro and micro-hardness tests. The formation of titanium diboride was found in all the synthesized test pieces (au)
[en] Kinetics of single boride needle growth during iron and steel boriding (Fe2B phase) is considered. Boride needle growth in axial and radial directions are determined by similar parameters, therewith decrease of axial growth rate results in increase of the radial growth rate. Decrease of the needle growth rate in axial direction (increase of radial growth) occurs: by increase of initial carbon content (C10) in steel; by increase of boron diffusion coefficient in boride (Dr); by decrease of carbon diffusion coefficient in solid solution (D11); by decrease of carbon equilibrium concentration in solid solution at boride interface (C1P)
[en] Calculations based on different micromagnetic models were carried out in order to describe the behavior of the ac susceptibiIity in the temperature range of the spin-reorientation transitions in hard magnets. It was found that the rotational susceptibility shows a sharp cusp at the transition temperature, while the contribution due to an increase in the domain- wall mobility is less significant. As well, there is a significant contribution of domain- wall processes to the overall susceptibility over the entire range of temperatures studied (80-- 180 K). For randomly oriented bulk samples, the susceptibility cusp has been experimentally observed. The susceptibility of randomly oriented powders shows only a moderate temperature dependence below the transition, followed by a sharp decrease at the transition temperature. The frequency dependence of the susceptibility showed the behavior expected for conducting samples, proving that domain-wall dynamics (e.g., aftereffects, lattice-defect--domain-wall interactions, etc.) do not play a role in the observed temperature dependence of the susceptibility
[en] Highlights: • Addition of B is not helpful for the formation of 1:13 phase in annealing process. • B prefers to form Fe2B rather than occupying interstitial sites in 1:13 phase. • Corrosion resistance of annealed LaFe11.6Si1.4By is improved with more B content. • The substitution of Fe2B for α-Fe phase reduces the galvanic corrosion rate. The co-influence of B and Si on the formation of 1:13 phase and corrosion behavior of LaFe13 − xSixBy alloys is investigated. 1:13 phase is found in as-cast LaFe11.6Si1.4B0.5, while there is no 1:13 phase in as-cast LaFe12.0Si1.0B0.5 with lower Si content. The addition of B in the LaFe13 − xSixBy alloys is not helpful for the formation of 1:13 phase during the annealing process. B element prefers to form Fe2B, rather than occupying interstitial sites in the crystal structure of 1:13 phase, which results in the decrease of the value of magnetic entropy change (| ΔS |). Corrosion behaviors of annealed LaFe11.6Si1.4By alloys are reported. The results show that the addition of B improves the corrosion resistance of the alloys. Polarization curves of single phase α-Fe, Fe2B and 1:13 phase show that the potential difference between Fe2B and 1:13 phase is lower than that between α-Fe and 1:13 phase, which lead to the enhancement of corrosion resistance. The corrosion of LaFe11.6Si1.4B0.3 is effectively suppressed, and the value of | ΔS | is only reduced by 28%.
[en] Graphical abstract: - Highlights: • The mass balance equations were formulated for the FeB and Fe2B layers grown on Fe Armco by gas-boriding. • The effect of boride incubation times was incorporated in the present model. • The boride incubation time was shorter for FeB phase. • The calculated boron activation energies in FeB and Fe2B were respectively close to 78.03 and 120.65 kJ mol−1. • The lower activation energy in FeB phase was characteristic of gas-boriding. - Abstract: The present work deals with a simulation of the growth kinetics of boride layers grown on Armco iron substrate. The formed boride layers (FeB + Fe2B) are obtained by the gas-boriding in the temperature range of 1073–1273 K during a time duration ranging from 80 to 240 min. The used approach solves the mass balance equations at the two growing fronts: (FeB/Fe2B) and (Fe2B/Fe) under certain assumptions. To consider the effect of the incubation times for the borides formation, the temperature-dependent function Φ(T) was incorporated in the model. The following input data: (the boriding temperature, the treatment time, the upper and lower values of boron concentrations in FeB and Fe2B and the experimental parabolic growth constants) are needed to determine the boron activation energies in the FeB and Fe2B layers. The obtained values of boron activation energies were then compared with the values available in the literature. Finally, a good agreement was obtained between the simulated values of boride layers thicknesses and the experimental ones in the temperature range of 1073–1273 K