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Abstract Effects of coverage layer on electrochemical corrosion behaviour and pitting morphologies of Mg-Al-Mn alloy subjected to massive laser shock peening (LSP) treatment were investigated by potentiodynamic polarisation test, electrochemical impedance spectroscopy (EIS), and scanning electron microscope (SEM) observations. Microstructures of Mg-Al-Mn alloy subjected to massive LSP treatment were also characterized. Results showed that LSP induced an obvious improvement in electrochemical corrosion resistance with increasing coverage layer. Even in a higher corrosive solution concentration, LSP could still prevent corrosion to some extent. The improvement in electrochemical corrosion resistance was due to the grain refinement and compressive residual stress induced by massive LSP treatment. Finally, the influence mechanism of the coverage layer on electrochemical corrosion behaviour of Mg-Al-Mn alloy was revealed. Graphical abstract Schematic illustration of the coverage layer on the electrochemical corrosion behaviour in NaCl solution. (a) The as-received, (b) the LSP-1, and (c) the LSP-4 specimen. Image 1 Highlights • LSP generated an obvious improvement in electrochemical corrosion resistance. • The increment of the coverage layer led to a stronger corrosion resistance. • Even in a more corrosive solution, LSP still prevent corrosion to a certain extent. • Influence mechanism of LSP coverage layer on corrosion resistance was revealed. [ABSTRACT FROM AUTHOR]

Highlights: [•] Re and Ru synergistic effects in nickel-based superalloys are investigated. [•] The Al site occupation of Re atom in the γ′ phase is observed directly. [•] The addition of Ru results in the repartitioning of Re to γ phase. [ABSTRACT FROM AUTHOR]

Abstract: The reaction mechanism of the interface among diamond, commercial Ni–Cr–P alloy and steel substrate has been studied by optical microscopy, scanning electron microscope, X-ray diffraction and Raman spectroscopy. The reaction layers formed among diamond, brazing alloy and steel substrate produced good wettability of diamond grits for achieving better quality tools. The reaction layer between diamond and brazing alloy comprised a reaction layer of brazing alloy and a reaction layer of diamond. Cr7C3 and Cr3C2 formed in the reaction layer of brazing alloy was the main reason for improving the bonding strength of Ni–Cr alloy to the diamond grits. A reaction layer of diamond may be a graphitization layer formed on the surface of diamond under high temperature brazing. The reaction layer of brazing alloy and steel substrate was the co-diffusion of Ni, Cr and Fe between the brazing alloy and the steel substrate. The life and sharpness of brazed diamond boring drill bits fabricated in this study were superior to the electroplated one in the market owing to its high protrusion and bonding strength. [Copyright &y& Elsevier]

The heat resistance of copper alloys is desirable to improve while it services at high temperature as electrically and thermally conductive components. In present paper, the strengthening pattern of nickel-based superalloys is expected to be applied in copper alloys. Here the Cu 50 Ni 37.5 M 12.5 (M = Al, Cr, Mo) alloys were prepared by vacuum arc melting and heat-treated in the corresponding conditions to obtain three different kinds of typical microstructure. The room temperature (RT) properties (hardness and resistivity) and high temperature properties (melting point, softening temperature and variable temperature resistivity) of the three alloys are contrasted and analyzed in detail. The Cu 50 Ni 37.5 Al 12.5 alloy strengthened through the γ′ phase coherent precipitation shows the best conductivity and highest hardness (5.47 %IACS (International Annealed Copper Standard) and 310.1 HV). The splitting of the γ′ phase is contributing to hardening at high aging temperature. The resistivity-temperature behavior of the three alloys shows that the resistivity with rising temperature consists of the ideal lattice resistivity and the resistivity increment due to the defects. The Cu 50 Ni 37.5 Al 12.5 alloy has the smallest room temperature resistivity and its resistivity maintains the lowest during the whole heating process (RT-1077K). Therefore, the coherent precipitated γ′ phase is expected to improve the heat resistance of the copper alloys while maintaining its electrical conductivity. Image 1 • The softening temperature of Cu 50 Ni 37.5 M 12.5 (M = Al, Cr, Mo) was studied. • The resistivity-temperature behavior of Cu 50 Ni 37.5 M 12.5 (M = Al, Cr, Mo) was interpreted. • The coherent precipitation of the γ′ phase could improve the heat resistance of copper alloys. [ABSTRACT FROM AUTHOR]

Abstract Effects of massive laser shock peening (LSP) treatment as a function of coverage layer on surface residual stress, microstructure, and corrosion fatigue (CF) resistance of Fe-Cr alloy were studied by X-ray diffraction technique, scanning electron microscope observations, and corrosion fatigue crack growth (CFCG) testing. Special attention was paid to the details of compressive residual stress and fracture morphology, and the influence mechanism of coverage layer on CF behaviour was also determined. Results indicated that LSP generated deeper compressive residual stress and effectively decreased the CFCG rate, and increased coverage layers further improved the corrosion fatigue life of notched specimens. Highlights • Laser shock peening generated compressive residual stress in the surface layer. • Laser shock peening effectively decreased the corrosion fatigue crack growth rate. • Increased coverage layer further improved the corrosion fatigue life of Fe-Cr alloy. • Special attention was paid to compressive residual stress and fracture morphology. • Influence mechanism of laser shock wave on corrosion fatigue life was determined. [ABSTRACT FROM AUTHOR]

The series of (Ge 0.8 Pb 0.2 ) 1− x Mn x Te alloys with x = 0, 0.03, 0.05, 0.08, 0.10, 0.13 and 0.18 were prepared by melting, quenching and spark plasma sintering (SPS) techniques. The effects of Mn on the phases and thermoelectric properties of the alloys were investigated. Experimental results show that all alloys are composites containing minor NaCl-type structure PbTe-based and major GeTe-based phases with the rhombohedral and the cubic structures without any phase arising from Mn. All Mn atoms were dissolved in these phases and reduce their unit cell. Mn atoms in GeTe-based phase can stabilize its high temperature cubic structure. The layer-like microstructures are formed by the Spinodal decomposition. All the samples show p-type conduction. Although the electrical resistivity for the alloy (Ge 0.8 Pb 0.2 ) 1− x Mn x Te increases, its Seebeck coefficient increases while its thermal conductivity reduces significantly as Mn content x increases due to the enhanced phonon scattering from the solute atoms Mn in these three phases and the microstructures. As a result, the figure of merit ZT of the (Ge 0.8 Pb 0.2 ) 1− x Mn x Te composites can be enhanced with proper Mn content. The maximum ZT of 1.3 was obtained in the sample (Ge 0.8 Pb 0.2 ) 0.9 Mn 0.1 Te at 723 K, which is much higher than that of Ge 0.8 Pb 0.2 Te alloy. [ABSTRACT FROM AUTHOR]

Abstract: Using the first-principles self-consistent discrete variational method based on the density functional theory, we have investigated the effect of B impurity on the kink in the [100](010) edge dislocation in bcc iron. Our energetic calculations show that the B has a strong segregation tendency to enter the kink. The structural energy, the interatomic energy, the partial density of states, and the charge density difference are also calculated in the present paper. All the results indicate that B in the kink can enhance the interatomic interaction between the impurity atom and the neighboring Fe atoms due to the hybridization of B 2p–Fe 3d4s4p orbitals. The introduction of B impurity leads to a strong pinning effect on the dislocation motion in bcc iron. [Copyright &y& Elsevier]

Here, an Fe 85.7 Si 1 B 10 C 1 P 2 Cu 0.3 diluted nanocrystalline alloy exhibiting relatively high B s of 1.69 T and low H c of 2.58 A/m is successfully developed. In addition, the effects of substituting C with P on the thermal behavior, magnetic properties, microstructure, and magnetic domains of Fe 85.7 Si 1 B 10 C 3−x P x Cu 0.3 (x = 0, 1, 2, and 3 at%) amorphous alloys are investigated. It is found that the addition of P not only improves glass forming ability, but also enhances thermal stability of the amorphous alloy. Furthermore, the suitable P addition can also optimize the soft magnetic properties under heat treatment. For the Fe 85.7 Si 1 B 10 C 1 P 2 Cu 0.3 alloy, the improved B s is due to the formation of bcc -Fe crystals and the lowest H c is caused by the low magneto-crystalline anisotropy, which are both induced by the construction diluted nanocrystalline structure. The formation of this unique microstructure is due to the competition between stabilization effect on amorphous phase of higher crystallization activation energy and the facilitation effect on the formation of bcc -Fe crystal by atomic-scale preexisting crystal-like clusters. • A novel Fe 85.7 Si 1 B 10 C 1 P 2 Cu 0.3 diluted nanocrystalline alloy exhibiting high B s of 1.69 T and low H c of 2.58 A/m is developed. • The suitable P addition can optimize the soft magnetic properties (SMPs) in FeSiBCCu nanocrystalline alloy system. • The competition between crystallization activation energy and the formation of bcc -Fe crystal leads to the excellent SMPs. [ABSTRACT FROM AUTHOR]

The low coercivity at high temperature and poor corrosion resistance limit the application field of Nd-Fe-B magnets. In this work, a DyCr film was prepared on the surface of Nd-Fe-B magnet through magnetron sputtering, and then subjected to grain boundary diffusion (GBD) to improve magnetic properties and enhance corrosion resistance. The results show that the residual Cr-rich film exists on the surface of NdFeB magnets, acting as a protective coating to enhance the corrosion resistance, which is evidenced by the weight loss experiment and scanning electron microscopy (SEM) image. Moreover, Cr element in the grain boundary phase increase the electrochemical potential from − 0.985 to − 0.733 V, which is also beneficial in improving corrosion resistance. Transmission electron microscope (TEM) analysis confirmed that the crystal structure of intergranular phase remained unchanged after diffusion, i.e. BCC-RE 2 O 3 (RE=Rare Earth) phase. The coercivity was improved significantly, obtaining an increment of 19.4% comparing to that of initial magnet, which is attributed to the formed Dy-rich shell with high magnetocrystalline anisotropy field and the improved distribution of grain boundary phase. This suggests that it is feasible to fabricate high coercivity magnets and strong corrosion resistance only through grain boundary diffusion, which is expected to further shorten the processing flow of Nd-Fe-B magnets. [Display omitted] • Corrosion resistance and magnetic properties are improved concurrently. • A Cr-rich film can act as a protective coating to enhance corrosion resistance. • The GBD does not change the crystal structure of intergranular phase. • Elemental metallurgical behavior and intergranular phase evolution are studied. [ABSTRACT FROM AUTHOR]

Ex-situ and quasi in-situ thermal exposure experiments have been conducted to explore the coarsening behavior of γ′ phases in the Ni-Al binary model single crystal superalloy at 1000 °C. It is obtained in ex-situ experiments that the number density and volume fraction of γ′ phases decrease with the exposure time increasing, while the average size increases. The coarsening of γ′ phases in the width direction obeys the cubic law described by the LSW theory, while the average size change in length is much greater than that in width. In quasi in-situ experiments, it is observed that small γ′ phases shrink or dissolute, the large ones tend to grow up. The coalescence of γ′ phases is also observed, which induces a sharp increase in the length direction. • Ex-situ and quasi in-situ thermal exposure experiments are carried out at 1000 °C. • Shrinkage or dissolution, growth and coalescence of γ′ phases are observed. • The smaller the size is, the faster the γ′ phases decrease. • The coarsening of γ′ phases in the width direction follows the LSW theory. • The coalescence of γ′ phases leads to a deviation from the LSW theory. [ABSTRACT FROM AUTHOR]

In this paper, long-term thermal treatment of a binary Ni–Al model nickel-based superalloy was performed at 1000 °C for 50 h, 100 h and 200 h. The evolution of the γ/γ′ interface was studied. As the treatment time increased, the γ′ precipitates coarsened and grew. Regular interface instability was observed that the shape of the γ/γ′ interface changed from flat to wavy. This interfacial instability was caused by the dynamic balance of strain energy and surface energy at the interface between the two phases. In addition, secondary γ′ precipitates were observed after long-term treatment and some of the larger ones took on pillow-like shapes. The pillow-shaped distortion was because that the growth rate of the cube vertices was faster than that of other locations due to the different strain states at different locations. [ABSTRACT FROM AUTHOR]

Highlights: [•] Pr-doped SnO2 hollow nanofibers were fabricated by electrospinning. [•] The crystal structures, surface morphology, chemical state and gas sensing performance were investigated. [•] The Pr-doped SnO2 hollow structure exhibited good gas-sensing properties to ethanol at 300°C. [•] The relationships between response time (recovery time) and temperature, response time (recovery time) and concentration were investigated. [•] A sensor mechanism of hollow nanofibers depend on temperature was discussed. [ABSTRACT FROM AUTHOR]