New Fe−Co−Ni−Cu−Al−Ti Alloy for Single-Crystal Permanent Magnets

A new alloy intended for single-crystal permanent magnets has been suggested. The new alloy has been designed based on the well-known Fe?Co?Ni?Cu?Al?Ti system and contains to 1 wt % Hf. The alloy demonstrates an enhanced potential ability for single-crystal forming in the course of unidirectional solidification of ingot. Single-crystal permanent magnets manufactured from this alloy are characterized by a high level of magnetic properties. When designing the new alloy, computer simulation of the phase composition and calculations of solidification parameters of complex metallic systems have been performed using the Thermo-Calc software and calculation and experimental procedures based on quantitative metallographic analysis of quenched structures. After the corresponding heat treatment, the content of high-magnetic phase in the alloy is 10% higher than that in available analogous alloys.     

Carbon nanotubes grown over Fe−Mo−Mg−O composite catalysts

High quality, high yield carbon nanotubes were synthesized on a composite catalyst using catalytic chemical vapor deposition. The composite catalysts Fe/MgO, Mo/MgO and (Fe, Mo)/ MgO, prepared via the solgel method using citric acid as fuel, were investigated for the production of CNTs. Only the (Fe, Mo)/MgO catalyst could support CNTs growth with high yield in this study. The different mole ratios between Fe, Mo, and Mg resulted in changes in product structure, diameter size, and yield. Decreasing the Fe concentration reduces the structural defects, and by increasing the Mo concentration, the yields of CNTs clearly increase.     

Correlation between the oxide impedance and corrosion behavior of Zr−Nb−Sn−Fe−Cu alloys

The correlation between the oxide impedance and corrosion behavior of two series of Zr−Nb−Sn−Fe−Cu alloys was evaluated. Corrosion tests were performed in a 70 ppm LiOH aqueous solution at 360°C for 300 days. The results of the corrosion tests revealed that the corrosion behavior of the alloys depended on the Nb and Sn content. The impedance characteristics for the pre- and post-transition oxide layers formed on the surface of the alloys were investigated in sulfuric acid at room temperature. From the results, a pertinent equivalent circuit model was preferably established, explaining the properties of double oxide layers. The impedance of the oxide layers correlated with the corrosion behavior; better corrosion resistance always showed higher electric resistance for the inner layers. It is thus concluded that a pertinent equivalent circuit model would be useful for evaluating the long-term corrosion behavior of Zr−Nb−Sn−Fe−Cu alloys.     

Amorphous phase formation in a Ni−Zr−Al−Y alloy system

Quaternary Ni-based amorphous alloys containing only metallic elements were developed through systematic alloy design. The importance of the phase equilibria information for the development of amorphous alloys was demonstrated through experimental results. Ni−Zr−Al ternary alloys having low liquidus temperature tend to have high GFA. Partial replacements of Zr with Y in the ternary alloys significantly enhanced the GFA of the quaternary alloys. The alloy Ni₆₀Zr₂₅Al₈Y₇ could be cast into a fully amorphous rod through an injection casting method. Since most Ni-based amorphous alloys reported to date contain non-metallic elements, the Ni-based amorphous alloys developed in the alloy system Ni−Zr−Al−Y are of interest.     

Hydrogen permeation properties of Pd-coated Ni−Nb−Ti−Zr amorphous alloys

Hydrogen permeability of Pd-coated Ni₆₀Nb₁₅Ti₁₅Zr₁₀ and Ni₆₀Nb₂₀Ti₁₅Zr₅ amorphous alloys was measured in the temperature range of 673 K to 773 K and was compared with the results obtained using Ni₆₀Nb₄₀, a binary amorphous alloy. The permeability thus measured was found to increase moderately increasing temperature. A long-term permeation test for the Pd-coated Ni₆₀Nb₁₅Ti₁₅Zr₁₀ amorphous alloy revealed high permeation stability up to 16.6 h.     

Dilatometric analysis on phase transformations of intercritical annealing of Fe−Mn−Si and Fe−Mn−Si−Cu low carbon TRIP steels

Evaluations of austenite fraction and transformation kinetics upon intercritical annealing of low carbon TRIP steels were attempted using quantitative dilatometric analysis. The measured dilation curves were analyzed by taking the carbon distribution between austenite and its decomposed phases into account. The amount of austenite formed during intercritical annealing and its carbon content obtained by dilatometric measurement was compared with the values predicted by thermodynamic calculations under the ortho-equilibrium and para-equilibrium conditions. The kinetics of the reaustenization process including pearlite dissolution and non-isothermal and isothermal formation of austenite could be quantitatively characterized by means of a modified JMAK (Johnson-Mehl-Avrami-Kolmogrov) equation.     

Refinement and strengthening mechanism of Mg−Zn−Cu−Zr−Ca alloy solidified under extremely high pressure

Mg?Zn?Cu?Zr?Ca samples were solidified under high pressures of 2–6 GPa. Scanning electron microscopy and electron backscatter diffraction were used to study the distribution of Ca in the microstructure and its effect on the solidification structure. The mechanical properties of the samples were investigated through compression tests. The results show that Ca is mostly dissolved in the matrix and the Mg₂Ca phase is formed under high pressure, but it is mainly segregated among dendrites under atmospheric pressure. The Mg₂Ca particles are effective heterogeneous nuclei of α-Mg crystals, which significantly increases the number of crystal nuclei and refines the solidification structure of the alloy, with the grain size reduced to 22 μm at 6 GPa. As no Ca segregating among the dendrites exists, more Zn is dissolved in the matrix. Consequently, the intergranular second phase changes from MgZn with a higher Zn/Mg ratio to Mg₇Zn₃ with a lower Zn/Mg ratio. The volume fraction of the intergranular second phase also increases to 22%. Owing to the combined strengthening of grain refinement, solid solution, and dispersion, the compression strength of the Mg–Zn–Cu–Zr–Ca alloy solidified under 6 GPa is up to 520 MPa.     

Strain-induced α-to-β phase transformation during hot compression in Ti−5Al−5Mo−5V−1Cr−1Fe alloy

The dynamic phase transformation of Ti?5Al?5Mo?5V?1Cr?1Fe alloy during hot compression below the β transus temperature was investigated. Strain-induced α-to-β transformation is observed in the samples compressed at 0?100 K below the β transus temperature. The deformation stored energy by compression provides a significant driving force for the α-to-β phase transformation. The re-distribution of the solute elements induced by defects during deformation promotes the occurrence of dynamic transformation. Orientation dependence for the α-to-β phase transformation promotion is observed between {100}-orientated grains and {111}-orientated grains. Incomplete recovery in {111}-orientated grains would create a large amount of diffusion channels, which is in favor of the α-to-β transformation. The effects of reduction ratio and strain rate on the dynamic phase transformation were also investigated.     

Ce−Mg

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Ce−Mg     

Ba−Nd

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Ba−Nd     

Cd−Nd

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Cd−Nd     

Ba−Sm

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Ba−Sm     

Cd−Pr

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Cd−Pr     

Ag−P

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Ag−P     

Al−La

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Al−La     

Ag−C

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Ag−C     

Pb−Sn

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Pb−Sn