Volume 110, Issue 12

The present study focuses on the microstructural evolution in Co–Re–Cr–Ni alloys at high temperatures. Four alloys with different Cr and Ni contents were studied. The microstructural examinations were performed using complementary methods of scanning electron microscopy, transmission electron microscopy, differential scanning calorimetry and neutron diffraction. Based on the experimental results and assisted by thermodynamic calculations, the effect of Cr and Ni on the microstructure could be identified. While both Ni and Cr, but Cr only if Ni is also present in the alloy, stabilize the fcc phase, the impacts of these elements on the σ phase formation are different. It was found that the temperature stability of the σ phase enhances with increasing Cr content, whereas Ni reduces the required Cr concentration for the σ phase formation. The evaluation of the Cr and Ni effects on the microstructural evolution contributes to a fundamental understanding of the alloy behaviour and, thus, is a key aspect for successful alloy development.

Light-weight magnesium alloys have great potential to be used in various fields due to their excellent combination of physical and mechanical properties. In crystals, hexagonal metals are distinct from cubic metals because they have a smaller number of slip systems and twinning activity. Sudden impact under a high strain rate causes complex deformation in magnesium alloys and limits their widespread use in defense and industrial applications. Complex deformation is also attributed to the initial processing history of the magnesium alloys. To systematically explain this complex dynamic behavior, this review focuses on the microstructural evolution of Mg alloys that were subjected to high strain rate compression. Moreover, unresolved problems and future targets are discussed in the “conclusion” section to more effectively understand the complex deformation behavior of Mg alloys described in this paper.

The glass formation, crystallization behavior, and soft magnetic properties of Fe 80− x Nb x B 20 ( x = 3, 6, and 9) and Fe 82.5− y Nb y B 17.5 ( y = 3.5, 5, 6, and 7) metallic glasses prepared by melt spinning were investigated. Differential scanning calorimetry analysis indicated that an increased Nb content results in increased thermal stability and glass-forming ability for both Fe 80− x Nb x B 20 and Fe 82.5− y Nb y B 17.5 glassy alloys. The supercooled liquid region increases from 26 to 50 K for Fe 80− x Nb x B 20 alloys and from 32 to 48 K for Fe 82.5− y Nb y B 17.5 alloys. Magnetic measurements reveal that saturation magnetization ranges from 65 to 137 emu g −1 for Fe 80− x Nb x B 20 glassy alloys and varies from 91 to 121 emu g −1 for Fe 82.5− y Nb y B 17.5 glassy alloys. The superior magnetic properties, high glass-forming ability, and low cost of raw materials make the current Fe–Nb–B ternary alloys promising for potential applications in the electronics industry.

Boron-carbonitride thin films were synthesized on Si (100) substrates by laser ablation, and the effect of deposition temperatures on the bonding structure and mechanical properties were studied to enhance the mechanical properties. The results of Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy demonstrated that B–N, B–C, N–C and N=C bonds coexisted in the thin films with the ternary B–C–N hybridization structure. The deposition rate decreased as deposition temperatures increased, and the hardness and modulus fluctuated between 14.5 and 27.2 GPa and 146 and 246 GPa, respectively. The law of evaluation of the mechanical properties with deposition temperatures was found to be related to the changes in the bonding structure, and the maximum hardness and modulus were 27.2 GPa and 246 GP, respectively, when deposition temperature reached 400°C.

Fe-0.8% P soft magnetic alloy was prepared by powder metallurgy. The compressibility and purity of powder were improved through collocation of powder particles and annealing treatment. The effect of sintering temperature on density, microstructure, and magnetic properties of the alloys was studied. Results show that the magnetic performance of the alloy was enhanced due to increased density because of the formation of liquid phase at low temperature and δ phase at high temperature. The optimum magnetic properties of Fe-0.8% P alloy with magnetic induction ( B 6000 ) of 1.83 T, maximum permeability of 18706 and coercive force of 30 A m −1 were obtained due to increased density (relative density 99.4%) and sintering temperatures.

Superhydrophobic surfaces with an excellent anti-icing performance were prepared on an aluminum substrate using a simple one-step spin coating method. The wettability, morphology, and surface compositions of the prepared surfaces were characterized using the measuring instrument for contact angle and sliding angle, scanning electron microscopy, and Fourier transform infrared spectroscopy, respectively. The contact angle of the as-prepared superhydrophobic surfaces was as high as 165 ± 1.5°, and the sliding angle was less than 5° for a 4 μL pure water droplet, indicating excellent superhydrophobicity and low adhesion. The effects of addition of ZnO powders in different amounts on the morphology and wettability were further analyzed. Moreover, the anti-icing performance of the superhydrophobic surfaces was investigated using a simple lab-made icing monitoring apparatus, and the results are discussed using the one dimensional heat transfer and classical nucleation theory. It was found that the theoretical icing time of the superhydrophobic sample was about five times longer than that of the reference sample whereas for the untreated aluminum, the contact angle was 72 ± 1.5°, which was nearly consistent with the experimental results. The present study demonstrates that the prepared superhydrophobic surface can delay the icing time and decrease the icing temperature, and could be found potential applications in various industries.

In the present work, the effect of reinforcement fiber diameter on elevated temperature bending creep deformation behavior of metal matrix composite is studied. Bending creep tests have been performed on Ni nanocomposite considering different fiber diameters using molecular dynamics simulations. Common neighbor analysis and dislocation analysis have been performed to analyze the deformation behavior and its underlying mechanism at the atomic scale during the bending creep process. Results have revealed that the specimen having thinner fiber exhibits better creep properties and higher plasticity due to the combined influence of shear band interactions and work softening. Whereas, work hardening and twin-detwin mechanisms are responsible for the quasi-cleavage fracture of the specimen having 4 nm diameter fiber.

This paper reports the comparative study of the microstructure, melting point, hardness and electrical resistivity of as-cast eutectic Sn-8.8 wt.% Zn, Sn-3.5 wt.% Ag, Sn-43 wt.% Bi and Sn-0.7 wt.% Cu lead-free solder alloys. Sn-3.5 wt.% Ag eutectic solder alloy was found to have the lowest electrical resistivity of 1.91 μΩ · cm whereas the highest electrical resistivity of 14.17 μΩ · cm was observed in the case of Sn-43 wt.% Bi eutectic solder alloy. The lowest melting point of 141.60°C was observed in the case of Sn-43 wt.% Bi eutectic alloy whereas the highest melting point of 243.28°C was observed in the case of Sn-3.5 wt.% Ag solder alloy. The results of the various solder alloys were compared with the properties of commercially available Sn-38.1 wt.% Pb eutectic solder alloy.

The current study investigated the effect of current density and plating time on structure and properties of Ni–W coating obtained by direct current electro-codeposition from a new deposition bath. Phase formation and microstructural changes of Ni–W alloy coatings were analysed by X-ray diffraction and scanning electron microscopy, respectively. Hardness and wear studies revealed better surface-mechanical properties with increasing coating time or current density due to higher W content and fine structure. Hardness values of coatings ranged from 346 Hv to 770 Hv and the coating obtained with 60 mA · cm −2 , 60 min showed the highest hardness (∼770 Hv) due to higher W content and finer structure. Potentiodynamic polarization testing and EIS study in NaCl solution revealed that finer morphology/strain tends to decrease corrosion resistance; whereas, higher W content improves it.

The present study emphasizes the effect on the properties of cathode material by doping Ln = Nd, Pr on A-site cation in double-layered perovskite (AA′B 2 O 5+ δ ). New cathode compositions Pr 1- x Nd x Ba 0.5 Sr 0.5 Co 0.5 Fe 1.5 O 5+ δ (where x = 0, 0.25, 0.5, 0.75 and 1.0) were synthesized by the glycine-nitrate method and their calcination temperature was optimized. Refinement of X-ray diffraction patterns was performed to determine crystallographic information of the obtained phase. These synthesized powders were pelletized, then sintered at 1200–1250°C for microscopic analysis and electrical conductivity measurements. The chemical stability of these compositions with electrolyte gadolinium-doped ceria was also investigated. Pr 1- x Nd x Ba 0.5 Sr 0.5 Co 0.5 · Fe 1.5 O 5+ δ at x = 0 has shown highest conductivity of 315 S cm −1 at 550°C followed by x = 1.0 of 230 S cm −1 at 570°C. The findings of the present study reveal that these compositions may be used as cathode materials in solid oxide fuel cells.