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Molybdenum has a broad application and good prospect in the field of nuclear energy, aerospace, electronics, etc., due to its high melting point, high hardness, corrosion resistance and other excellent performances. In this paper, an isothermal and isochronous annealing heat treatment, at the temperature of 800–1300 °C for 0.5–2 h, was applied to pure molybdenum (PM) sheets with deformation of 70%, 80%, 90%, and 95%. The initial deformation of the PM sheet was increased from 70% to 95%. After annealing at 900–1200 °C for 1 h, the recrystallized grain size gradually decreased. The Goss texture ({110}<001>) was always present in the pure molybdenum sheet with 95% deformation during heat treatment, but its strength decreased with the increase of the temperature. The copper texture ({112}<110>) deflected to a cubic texture, and its orientation changed from {001}<110> to that of cube texture {110}<100>. With the increase of the temperature, the cubic texture was obtained more easily in the pure molybdenum sheet. The recrystallization nucleation mechanism of the pure molybdenum sheet with 95% deformation was mainly in situ nucleation and orientation nucleation. The Avrami index of the pure molybdenum sheet with 95% deformation was calculated by the JMAK equation and found to be 3.6. [ABSTRACT FROM AUTHOR]

This research investigated the microstructure, corrosion behavior and mechanical properties of iron and holmium modified Sn-3.0Ag-0.5Cu solder alloy with ultrasonic treatment. The results demonstrated that the distribution of the phases in the ultrasonically treated solder alloys became homogeneous and the microstructure of ultrasonically treated solder alloys were more refined. The average grain size of ultrasonically treated solder alloys was reduced from 206.7 μm to 184.1 μm. A significant increase in the tensile strength from 38.75 MPa to 47.38 MPa was found in the ultrasonically treated solder alloys. The polarization curves results indicated that the solder alloys treated with ultrasound possessed lower corrosion current density and the results of atomic force microscopy suggested that roughness of corrosion products morphology was reduced. Furthermore, the electrochemical impedance spectroscopy (EIS) results indicated that the ultrasonically treated solder alloys had larger diameter of the semicircular loops and higher total impedance values. • Ultrasound was applied and fabricated iron and holmium modified Sn-3.0Ag-0.5Cu solder alloy with ultrasonic treatment. • The average grain size of ultrasonically treated solder alloys was reduced from 206.7 μm to 184.1 μm. • The ultrasonically treated solder alloys exhibited excellent corrosion resistance. • The ultrasonically treated solder alloys presented better mechanical properties. [ABSTRACT FROM AUTHOR]

EA4T steel has been widely used in the manufacture of railway axles. Laser cladding remanufacturing technology has been used to repair railway axles, and the failure behaviors of railway axles has been studied. In this work, a class of original FeCrNiMo alloy layers that contain rare-earth elements was successfully fabricated through a laser cladding technique on EA4T steel substrates. The microstructure and elemental distribution of the cladding layers were analyzed through scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron probe microanalysis (EPMA). Simultaneously, the microhardness, bond strength and fatigue properties of different samples were determined. The results indicated that the phase composition of the cladding layer was mainly martensite. The grains in the cladding layer were gradually refined with an increase in the distance from the interface, and the chemical composition distribution was more uniform. At the same time, the bonding property of the cladding layer and matrix was good, and the fatigue strength of the sample was improved. [ABSTRACT FROM AUTHOR]

Co Ni and 5% Fe doping Co Ni alloy coatings are prepared on SUS 430 substrates as interconnect protect layers for solid oxide fuel cells by electroplating. The electrical characteristics and oxidation resistance of interconnects are enhanced by the alloy coatings after they are oxidized in air at 800 °C for 1000 h and the Co-Ni-Fe alloy coatings showing the better effect. Cr is unable to diffuse outward owing to the multi-layer oxidation structure. Addition of Fe to Co Ni alloy coatings leads to the formation of a (Fe,Co,Ni) 3 O 4 spinel layer with lower activation energy and stronger ability to restrict oxygen diffusion inward. • Two interconnect protective coatings were prepared by electroplating method. • The multilayer oxidized structure prevented the outward diffusion of Cr. • Co-Ni-Fe coated steels exhibited excellent oxidation resistance and lower ASR. • Co-Ni-Fe converted coatings were further characterized by TEM and EPMA. • (Fe,Co,Ni) 3 O 4 layer had excellent electrical properties and thermodynamic stability. [ABSTRACT FROM AUTHOR]

The addition of polyamide veil (PAV) to the interlaminar area of carbon fiber (CF) fabric/epoxy composites can effectively increase their toughness with high accuracy. Vacuum-assisted resin infusion (VARI) was used to fabricate composite structures. VARI was applied to obtain a PAV, which is an interleaf between fabric piles of CFs. The thermoplastic PAV was dissolved in epoxy when the PAV was cured at high temperature. A phase-separated morphology with a PAV-rich secondary phase was formed during the curing process. Experimental results indicated that compression after impact (CAI), which is the average value of CAI, increased by threefold when two layers of PAV were added. The thermal and mechanical characteristics of the composite were analyzed and compared at room temperature and high-temperature wet conditions. [ABSTRACT FROM AUTHOR]

EA4T steel has been used widely in railway axles. Considering the failure behavior of railway axles and other solving methods, laser cladding remanufacturing was used for repairing the railway axles. The microstructure and fatigue fracture mechanism of EA4T steel in laser cladding remanufacturing were investigated by optical microscope (OM), scanning electron microscope (SEM) and X-ray diffraction (XRD). The fatigue life and fatigue crack growth were measured by three-point bending experiments. The microstructure of cladding layers was composed of columnar crystal and fine dendrites, and the main phases of cladding layers were γ and Fe 2 B shown by XRD results, which lead to the highest micro-hardness value in the cladding layer. The da/dN-ΔK curves and fracture morphologies indicate that the cladding layers could delay the fatigue crack initiation and improve the fatigue life of EA4T steel. [ABSTRACT FROM AUTHOR]

Fe314 coatings were prepared on EA4T steel by laser cladding method, and were respectively subjected to 550 ℃ × 2 h Two kinds of heat treatment: annealing and annealing (1150℃×1h + 980℃×1h + 650℃×2h) after normalizing twice. The microstructure of the precipitated phase after heat treatment, the impact toughness and microhardness of the coating reveal the mechanism of heat treatment to improve the strength and toughness of the cladding layer. The results show that the Fe314 cladding layer had good plasticity and good room temperature strength after adopting the two-stage heat treatment process. The average microhardness was 228HV and the impact toughness was 64 J. The impact toughness of the cladding layer was related to the morphology and grain size of the precipitates. A large number of dimples can be observed on the impact fracture morphology, indicating that the fracture mechanism of the alloy was mainly ductile fracture. Comprehensive comparison, the comprehensive properties of strength and toughness were better at 1150℃×1h and 980℃×1h followed by 650℃×2h heat treatment. [ABSTRACT FROM AUTHOR]

Abstract: Cu6Sn5 fiber reinforced Sn in situ composites with a nominal composition Sn–1Cu (wt%) were produced by specially controlled directional solidification using a laboratory-scale Bridgman furnace equipped with a liquid metal cooling (LMC) device. The microstructure of as-produced composites was characterized by using optical microscopy (OM), electron microscopy (SEM) and microanalysis (EDX). The tensile strength and plasticity at room temperature were examined by tensile tests. The microstructure observation showed that the microstructure consisted of β-Sn matrix and fiber-like Cu6Sn5 intermetallics compounds (IMCs). For a constant temperature gradient (12Kmm−1), it was found that the spacing between Cu6Sn5 fibers and diameter of single crystalline Cu6Sn5 fiber were mainly controlled by the solidification rate (V), and both of them decreased with increasing solidification rate. The strength was dominated by the Cu6Sn5 fiber alignment, such as the spacing and diameter. Thus the tensile tests results have been correlated to fiber spacing (λ) and diameter (d), since fiber growth has prevailed along all obtained Sn–1Cu samples. It was found that the ultimate tensile strength (UTS) and yield tensile stress (YS) initially increased with increasing solidification rate which ranged from 5 to 60μms−1, and decreased with further increasing solidification rate, such as 100μms−1. In contrast, the elongation (EL) decreased with increasing solidification rate due to the increased amount Cu6Sn5 IMC quantity. [Copyright &y& Elsevier]

In this work, the microstructure, electrochemical and mechanical properties of Sn-3.0Ag-0.5Cu solder alloy with Fe and Ho additions were studied. The results demonstrated that adding of Fe and Ho improved the microstructure of solder alloy and formed FeSn 2 phase and Ho 5 Sn 3 phase. Besides, the addition of Fe weakened the microhardness and tensile properties of the solder alloy, which was ascribed to a weak interface between FeSn 2 and β-Sn matrix. The microhardness and tensile properties of solder alloy were enhanced by adding Ho owing to the improvement of microstructure and the strengthening of the second phase. Electrochemical tests and atomic force microscopy (AFM) results showed that comparing to the base solder alloy, higher corrosion current densities and rougher surfaces after corrosion were found in the solder alloys with the Fe and Ho additions. • The Fe and Ho were added to Sn-3.0Ag-0.5Cu solder alloy. • The addition of Fe was detrimental to the corrosion resistance, while Ho could reduce the negative effect. • The mechanical properties of the solder alloy decrease and then increase. • Fracture mode turned from ductile fracture to mixed ductile-brittle fracture. [ABSTRACT FROM AUTHOR]

In this study, the effects of the thermal gradient (TG) applied during the bonding process on the microstructure, grain orientations and shear properties of Cu/SAC305/Cu solder joints were investigated, and the magnitude of the TG was controlled by the thickness of the solder layer. The results indicated that the introduction of TG caused the asymmetric growth of intermetallic compounds (IMCs) and enabled the rapid generation of IMCs at the cold end. Cu 6 Sn 5 , as the main component of IMCs in Cu/Sn solder joints, developed a strongly preferred orientation in the (0001) ‖ RD direction. While for β-Sn grains, the preferred orientation was uncontrollable, which formed the preferred orientations of (010) ‖ TD, (031) ‖ RD and (114) ‖ RD at 20 um, 60 um and 100 um solder joints, respectively. In addition, the TG reduced the reliability of solder joints whose shear properties were lower than those of joints with isothermal bonding. • Thermal gradients were successfully introduced into the soldering process of Cu/Sn joints. • Solder joints with full IMCs were manufactured rapidly. • Cu 6 Sn 5 grains exhibited directional growth of the c-axis along the thermal gradient. • Under the same conditions, solder joints bonded by thermal gradients exhibit poorer mechanical properties. [ABSTRACT FROM AUTHOR]

• The Fe-Cr-Ni based composite coating was prepared using laser cladding method. • The addition of rare earth elements makes the cladding layer more dense and more refined. • Increased tensile strength, increased yield strength and increased impact value. Laser cladding technology was used to prepare Fe314 coating with added CeO 2 and La 2 O 3 on the surface of EA4T steel. The microstructure and structure of the coating were analyzed using scanning electron microscopy, electron probe microanalyzer, and X-ray diffraction. The mechanical properties of the coating were tested using a microhardness tester, universal testing machine, and pendulum impact testing machine. The results show that the addition of rare earth elements makes the cladding layer more dense and more refined; at the same time, compared to the base material, the tensile strength of the repaired specimen increased by 12.9 %, the yield strength increased by 23.3 %, and the impact value increased by 43.6 %. [ABSTRACT FROM AUTHOR]

The laser cladding additive manufacturing technology and high-entropy alloys can serve as ideal techniques and materials for the surface repair of high-speed train axles. Coatings of FeCoCrNiMox (x = 0.2, 0.5) were prepared on EA4T axle steel using laser cladding technology, and their phase, structure, and mechanical properties were analyzed using X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI) characterization techniques. Additionally, the mechanical properties of the coatings were tested, and first-principles calculations were used to verify and calculate the material's mechanical performance. The research findings indicate that an increase in Mo content leads to a greater degree of lattice distortion, causing a leftward shift in diffraction peak positions. Significant differences in the microstructure from the substrate to the coating surface were observed, with columnar grain structure at the bottom of the cladding layer and equiaxed dendrites dominating the coating surface. The increase in Mo content promotes the formation of σ phase while also refining the grain size. ECCI results show that both types of coatings consist of a high-density dislocation cell structure and Mo-rich particles. With an increase in Mo content, the peak hardness of the coating increased from 456.5 HV to 469.4 HV, while the impact energy decreased from 56 J to 16 J, attributed to the increase in dislocation density and the greater quantity of σ phase. First principles calculations verified that the comprehensive mechanical properties of FeCoCrNiMo 0.2 are superior, providing theoretical guidance for the optimization and design of the coatings. Experimental method to explore the Mo element of first principles calculation of laser cladding high entropy alloys FeCoCrNiMox (x = 0.2, 0.5) organization and mechanical properties of impact. [Display omitted] • High entropy alloy coatings with different Mo content were prepared by laser cladding. • Mo element promotes the formation of σ phase and has the effect of refining the grain. • Increasing the Mo content significantly raises the hardness and reduces the toughness. • First principle calculation confirms that FeCoCrNiMo 0.2 has better mechanical properties than FeCoCrNiMo 0.5. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the effects of In and aging treatment on the microstructure, mechanical properties and electrochemical corrosion behavior of Sn 2Cu solder alloy. It is found that In could refine the β-Sn grains, resulting in an improved microstructure and enhanced microhardness and tensile properties. Moreover, adding In lowered the undercooling of the Sn 2Cu solder alloy, with a maximum reduction of 5.97 °C. The corrosion resistance of the alloy was also dramatically improved by In addition, as evidenced by: (1) a lower corrosion current density compared to the matrix alloy; (2) a smaller surface roughness and pit depth after corrosion; (3) an increased ratio of SnO 2 in the corrosion product layer. On the other hand, aging treatment had an adverse impact on the mechanical properties, but a beneficial influence on corrosion resistance of solder alloy. • In and aging treatment effectively changed the mechanical and electrochemical properties of Sn 2Cu solder alloys. • In significantly increased the ratio of SnO 2 in the corrosion product layer of solder alloys • In dramatically reduced the undercooling and pasty range temperature range of Sn-2Cu solder alloys [ABSTRACT FROM AUTHOR]

A novel two-step joining technology (pyrolysis and C–Si reaction bonding) to prepare in-situ SiC nanowires reinforced SiC/SiC joints were developed. The multi-component slurry consisting of polycarbosilane (PCS, preceramic polymer) and ferrocene (catalyst) were designed and optimized to join the sintered SiC ceramics. Microstructure of the joining layer after pyrolysis and joints after C–Si reaction bonding were analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). In addition, PCS-derived products and growth mechanism of SiC nanowires inside the joining layer were discussed. The results showed that 4 wt% castor oil and 3 wt% phenolic resin were proven to be the optimized dispersant content and binder content of the slurry to obtain the top-quality joining layer. With the increase of PCS content in the slurry, the generated SiC nanowires inside the joining layer became straight and diameter increased. After C–Si reaction bonding, the SiC nanowires were retained and distributed randomly in the joining layer. PCS-derived products after pyrolysis consisted of β-SiC and free carbon, and later gradually increased with rise of pyrolysis temperature. The SiC nanowires inside the joining layer grew up following the Vapor-Liquid-Solid (VLS) mechanism and gaseous substances used for the growth were mainly comprised of CH 4 , SiH 4 and CH 3 SiH 3. Image 1 [ABSTRACT FROM AUTHOR]