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P91 and P92 steels are widely used in nuclear and thermal power plant's high-temperature (650–700 °C) operating components. The welding procedure, base plate composition, filler material composition, and post-weld heat treatment (PWHT) significantly affect the metallurgical characterization of weldments at room temperature. This work focuses on joining P91 and P92 steel by the TIG welding with filler ER90S-B9. The study analyzes the materialization of coarse-grained HAZ (CGHAZ), inter-critical HAZ (ICHAZ), and fine grained HAZ (FGHAZ) under welded and PWHT. PWHT was conducted at 840 °C for 2, 4 and 6h. An optical microscopic (OM) scanning electron microscope (SEM) was employed to characterize the welded and PWHT samples. It was perceived that the tensile strength of PWHT increased as the heat treatment times increased from 2 to 6 h, while the hardness value decreased accordingly. The maximum tensile strength (594.71 MPa) was observed in PWHT_6 h, while the minimum tensile strength (537.52 MPa) was perceived in the as-welded sample. The PWHT_6h reveals the minimum hardness values (271.12 HV) at the fusion zone among all the conditions. The WFZ consisted of an untampered lath martensitic grain structure, demonstrating an average hardness value of 314.15 HV in the PWHT_2h condition. The hardness value in CGHAZ samples for as-welded, PWHT_2h, PWHT_4h, and PWHT_6h was observed at 456.85, 436.81, 368.63, and 327.41 HV, respectively. [ABSTRACT FROM AUTHOR]

This paper characterizes the efficacy of borax on different properties of alkali-activated materials (AAMs). Fly ash (FA) and ground granulated blast slag (GGBS) were used as base substances at different ratios. The effects of borax on workability, compressive strength, efflorescence formation and crack resistance are the main ideas of the study. The results indicated the positive effects of borax on the properties of one-part fly ash/slag-based alkali-activated materials such as increasing workability and decreasing efflorescence. The microscopic images and scanning electron microscope (SEM) showed that the addition of borax reduced the cracks and a higher amount of slag made the samples denser with less unreacted raw materials, respectively. The compressive strength test results showed that borax had a detrimental impact at early ages with a positive effect at later ages. Binders with borax and 20-25% replacement of FA with GGBS were found to have the best performance when workability, compressive strength, efflorescence formation, and cracks on the samples were taken into account. [ABSTRACT FROM AUTHOR]

In this study, the effects of different composition V-Mn-Cr inoculants on the microstructure and mechanical properties of GCI were investigated through Optical microscope (OM), Scanning electron microscope (SEM), Energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), etc. The results showed that the optimum quantity of inoculant was 7% V, 1% Mn and 6% Cr, and compared with the commercial inoculant samples, the tensile strength, Brinell hardness, and elastic modulus of the V-Mn-Cr inoculant samples increased by 16.7%, 14.2%, and 12.8%, respectively. V-Mn-Cr inoculants were found to refine austenite, graphite, pearlite and eutectic cells size, reduce pearlite lamellar spacing, and increase pearlite and eutectic cells number, thus improving mechanical properties. In addition, graphite nucleation substance may consist of oxides (SiO2, FeO, Cr2O3), carbides (SiC, TiC), sulfides (MnS, FeS), and XO·SiO2 silicates (X: Mn, Fe, Ca). [ABSTRACT FROM AUTHOR]

The main aim of this research work is to investigate the high-temperature cyclic corrosion performance of the wrought and direct metal laser sintered (DMLS) alloy 718 in the air and molten salts NaCl-90%Na2SO4 and three salt mixture (3SM) Na2SO4-10%V2O5-10%NaCl atmosphere for 120 h at 800°C. The microstructure of the wrought and DMLS alloy illustrated the austenitic and dendrite structure. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to evaluate the structure and phase constitutions of the scale. Visual and microstructural evaluation of the alloy post-exposure indicates that corrosion is more prevalent in molten salt conditions, when compared to air, and Cl-species induced the active oxidation in molten salt. The oxide film development and damage mechanism were detailed and explained by a cross-sectional investigation. Significant spalling and sputtering were also noticed in the S3 salt mixture. This might be attributed to the rapid formation of oxide scales by vanadate, followed by dissolution of the oxide in molten sulphate and chloride. The results divulged that both AM-built and wrought alloy exhibited the similar corrosion properties and both the alloys were undergone severe degradation in MS condition. Highlights Alloy 718 was fabricated successfully by the direct metal laser sintering (DMLS) method. Cyclic high-temperature oxidation and corrosion of the alloy were studied at 800°C. The oxidised sample exhibits a lower weight gain with no damage. Due to chlorination and sulfidation, the corroded samples exhibited more oxidation and susceptible. [ABSTRACT FROM AUTHOR]

The aim of this work is to develop the precursor-based Al foam by deposition of AA6063-T6 consumable rod, filled with a foamable mixture of titanium hydrate (TiH2) and aluminium powder over a mild steel substrate through friction stir deposition (FSD) technique. The AA6063-T6 consumable rods were drilled with different hole strategies ranging from 1 to 6 holes on the periphery of the rod, which were filled with foaming powder of the same composition. To perform the deposition, a conventional vertical milling machine was used. The deposited material presents a fine equiaxed grain whose size is much lower than the as-received material, indicating dynamic recrystallization during friction stir deposition. The results also show that the foaming particles decrease the hardness values of the produced deposits when compared to those of base material. It has been observed that 4 and 5 numbers of holes in the consumable rod are more suitable for foam development and the foaming particles are more uniform as obtained from energy dispersive spectrum (EDS) and scanning electron microscope (SEM) analysis. It is also observed that by increasing the number of holes in the rod more than 5 promote the formation of defects in the developed foam. The consumable rod with 4 and 5 holes shows the linear plateau stress in the compressive test as compared to 1, 2, 3 and 6 holes. [ABSTRACT FROM AUTHOR]

Micro-arc oxidation (MAO) technology, as an efficient and widely used technology, can fabricate a ceramic film on magnesium (Mg) alloys in situ to significantly improve corrosion resistance. The study aims to investigate the effect of voltage modes on the preparation and performance of MAO coating on Mg alloys. The scanning electron microscope, X-ray diffractometer, potential dynamic polarization, and electrochemical impedance spectroscopy measurements were applied for characterizing the microstructure, composition, and corrosion resistance of the MAO film, respectively. The results revealed that employed 300/350 V step-up mode, the MAO film showed a more uniform distribution of surface micro-pores, fewer micro-cracks and denser inner layer, lower corrosion current density (1.871 × 10−3 mA·cm−2), and higher electrochemical impedance value, compared to other voltage treated parameters. Therefore, it could be concluded that the step-up voltage parameters are conducive to the optimization of microstructure, improvement of corrosion resistance of MAO coating, and reduction of the energy consumption during processing. [ABSTRACT FROM AUTHOR]

The effect of Ce on inclusion evolution in the Al-killed high-strength steel is investigated through experimental observations and thermodynamic calculations. The microstructures are analysed by scanning electron microscope (SEM), optical microscope (OM) and electron backscattered diffraction (EBSD) analysis. Mechanical properties tests are carried out to study the effect of Ce on the tensile and impact properties. The results show that after Ce treatment, the typical inclusions are modified from Al2O3 inclusions and Al2O3+MnS complex inclusions to Ce-O-S inclusions, and the inclusions are refined. The area fraction, size and length/width ratio of martensite-austenite (M-A) constituents decrease with the addition of Ce. In the Ce-containing steel, the grains are finer, and the proportion of high angle grain boundaries and low-Σ coincidence site lattice boundaries is higher. Ce can improve the plasticity and impact toughness of the steel while maintaining high strength. [ABSTRACT FROM AUTHOR]

The coral-sand (CS) foundations built in the marine environment inevitably suffer from chemical invasion of seawater. Graphene oxide (GO) has been considered as a feasible additive to improve chloride penetration ability of cement mortar, but limited studies have been carried out on GO-modified CS cement stones. In this study, a series of rapid chloride migration (RCM) tests were respectively conducted on CS or river-sand (RS) cement stones with various GO contents. Meanwhile, scanning electron microscope (SEM) tests were also performed to study microscopic features of the cement stones. Experimental results revealed that the chloride migration coefficient DRCM for both CS and RS samples firstly decreased and then increased with increasing GO content. The lowest DRCM values were achieved while adding 0.02 wt% GO for CS samples and 0.03 wt% GO for RS samples. Meanwhile, the DRCM values of CS samples were higher than those of RS samples at a given GO content. Microstructural results demonstrated that as the GO content increased, the shape of hydration crystals gradually transformed from a needle-like shape to a flower-like shape. The addition of GO could promote hydration products to fill the holes inside the cement stones, effectively inhibiting the chloride ion penetration. [ABSTRACT FROM AUTHOR]

The corrosion behaviour of the closed-cell aluminium foam made of Al 6101 alloy in different heat regimes such as heat treatment (HT), cryogenic treatment (CT) and cryogenic heat treatment (CHT) are investigated in this research work. The Electrochemical Impedance Spectroscopy (EIS) and DC polarisation are the techniques employed in this research work. The microstructure, surface morphology and composition of the treated foam samples are evaluated using a high-resolution Scanning Electron Microscope (SEM) and Energy Dispersive Analysis of X-rays (EDAX). The polarisation and electrochemical impedance measurements of the CT and HT foam samples reveal appealing results in the corrosion resistance when comparing with untreated foam sample. From the SEM images, it is evident that the deep cryogenic treatment changes the morphology of Al 6101 foam and the formation of the Guinier-Preston (GP) zone increases the density of dislocation. [ABSTRACT FROM AUTHOR]

Micro-arc oxidation (MAO) coatings were fabricated on 2195 aluminium-lithium alloy substrate, using a silicate and phosphate electrolyte with variable scandium nitrate (Sc(NO3)3) concentrations. The properties of the coatings were analysed by scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical workstation. The comprehensive analysis demonstrates that adding proper amount of Sc(NO3)3 increased the oxidation voltage, which transformed the worm shape discharge micropores into round-hole shape, and the MAO coatings presented a double-layer structure. The primary phase composition of the coatings was γ-Al2O3, α-Al2O3, Sc2O3 and Al3Sc. The optimum concentration of Sc(NO3)3 was 0.6 g L−1. The hardness reached a maximum value of (1284 ± 43.5) HV, which was about 2.5 times higher than that without adding. The self-corrosion current density reduced from 138.00 × 10−7 A cm−2 (substrate) to 3.65 × 10−7 A cm−2, which was approximately two orders of magnitude lower, indicating that the corrosion resistance was improved. [ABSTRACT FROM AUTHOR]

Identification of wool and cashmere has attracted considerable attention in various research fields due to the outstanding properties of fibers. Herein, the hollow-like carbon tubes were facilely prepared by carbonization using the waste wool fibers, which were further characterized by elemental analysis and scanning electron microscope (SEM). After carbonization, hollow-like structures were observed in wool, while cashmere still presented in solid shapes at cross-sectional morphologies. Furthermore, the medulla existed in wool can be pyrolyzed after the carbonization process, which may be an effective way to distinguish the cashmere from wool by their obvious differences in fiber shapes, fiber sizes and residual weights. The effects of temperature on the properties of wool and cashmere were also analyzed. The proportions of hollow wool tubes increased with the rise of temperature, reaching more than 90% at 500°C. Apart from that, the mean diameter of treated wool (16.022 μm) was larger than treated cashmere (8.399 μm), which both shrunk nearly 50% than pristine fibers, and the residual weight of cashmere (68.95%) was higher than wool (62.98%). This method could be extended for identifying specialty fibers like fine yak fiber and yak hair, paving the way for distinguishing protein fibers in multiple areas. [ABSTRACT FROM AUTHOR]

Engineering properties of cemented soil in deep cement mixing (DCM) walls significantly affect security and stability of foundation pit, especially in regions where silty and sandy layers are widely distributed. This article investigates properties of cemented silt improved with calcium bentonite and phosphogypsum, in order to realise economic and environmental benefits. A series of laboratory tests, including unconfined compression strength (UCS) tests, hydraulic conductivity tests and scanning electron microscope (SEM) tests are carried out to examine strength, deformation, hydraulic behaviour and microstructure of solidified silt. The results show that the growth of unconfined compressive strength is as high as 86 ∼ 166 per cent with the addition of optimal content of calcium bentonite and phosphogypsum. The hydraulic conductivity of cemented silt decreases by one to two orders of magnitude with increasing additives and curing time. Moreover, the SEM pictures account for the existence of an optimal content of phosphogypsum explicitly. The microstructure of specimens reflected by SEM pictures shows a high consistency with UCS tests and hydraulic conductivity tests. Laboratory tests and cost analysis indicate that calcium bentonite and phosphogypsum have potential applications as binders in construction of DCM walls. [ABSTRACT FROM AUTHOR]

In this paper, the effect of Er on the hot cracking behaviour of Al-5Cu alloy is investigated by the means of wedge moulds, differential hot analyzer, optical microscope, and scanning electron microscope. The results show that the percentage of intergranular low-melting-point eutectic structure is increased by approximately 8% on average per 0.3 wt-% Er additions. The increase of low-melting-point eutectic structure enhances the fluidity of the liquid film in the late solidification stage, resulting in the improvement of the hot cracking resistance of the alloy. Moreover, the Al-5Cu-0.6Er alloy has the best hot cracking resistance under wedge-shaped copper casting experiments. [ABSTRACT FROM AUTHOR]

Rice husk ash (RHA) is an agricultural by-product obtained from incineration of abundantly available rice husk (RH) which can be used as a substitute for cement. In this study, RHA up to 30% has been utilized as partial replacement of cement by weight along with fly ash as one of the components in self-compacting concrete (SCC). Experimental programs were conducted to evaluate the fresh properties of SCC. Strength properties i.e. compressive strength, splitting tensile strength, and durability properties such as sorptivity, water absorption & porosity, rapid chloride permeability test (RCPT), sulphate resistance were also evaluated up to the age of 365 days. It was found that the inclusion of RHA up to 15% had a positive effect on strength properties while durability properties improved significantly at all replacement levels of RHA. The compressive strength results were verified with microstructure analysis using scanning electron microscope (SEM). Moreover, it was observed that material cost savings of up to 18% can be achieved by using up to 30% of RHA along with reduction in the carbon footprint and embodied energy. Multi linear regression models were established to predict the strength and durability properties at different curing ages and replacement levels of RHA. [ABSTRACT FROM AUTHOR]

This paper studied the strength growth characteristics of Tianjin Binhai dredger fill, considering the impact load, drainage condition, and loading way of the impact. Based on UU and scanning electron microscope tests, the strength growth mechanism of the dredger fill was studied from both macroscopic and microscopic perspectives. The results showed that there an optimal impact load under the combined action of impact load and drainage, which can enhance the strength of the dredger fill to the maximum extent, its value is close to the structural yield stress. Furthermore, the methods of 'more impact rounds and fewer impact counts' and 'first light then heavy' can obtain the best effect of foundation reinforcement. Microstructural analysis showed that, with the increase in impact loads, the pore complexity and the number of pores increased, while the porosity, the number of soil particles, the pore circumference, and the total pore area decreased. This research also showed that the increase in the strength of dredger fill was mainly reflected by the increase in the internal friction angle under the combined actions of impact load and drainage, while the change of cohesion was rather small. The mathematical relationship between the internal friction angle and the pore characteristic can be expressed by a unary function, which increases with increasing pore complexity. [ABSTRACT FROM AUTHOR]

The structure and mechanical properties of non-equiatomic Al8Co30Cr18Fe9Ni31Nb4, Al8Co30Cr18Fe9Ni31Nb2Ti2 and Al8Co30Cr18Fe9Ni31Ti4 high entropy alloys (HEAs) were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), hardness and tensile testing. TEM and XRD analyses revealed the formation of γ''-Ni3Nb/γ (FCC), double FCC and γ'-Ni3Al/γ (FCC) structure for as-cast Al8Co30Cr18Fe9Ni31Nb4, Al8Co30Cr18Fe9Ni31Nb2Ti2 and Al8Co30Cr18Fe9Ni31Ti4 HEAs, respectively. The hardness and yield strength values were found to increase with the addition of Nb while the ductility of alloys increased with the increase in Ti concentration, significantly. The as-cast Al8Co30Cr18Fe9Ni31Ti4 alloy exhibited an excellent combination of ultimate tensile strength of 844 MPa and an elongation of 29.8% due to the coherent phase relation between γ' precipitates and γ matrix. The fractured surfaces of as-cast Al8Co30Cr18Fe9Ni31Nb4, Al8Co30Cr18Fe9Ni31Nb2Ti2 and Al8Co30Cr18Fe9Ni31Ti4 HEAs showed typical dimple type ductile fracture under tension test. [ABSTRACT FROM AUTHOR]

To explore the microscopic mechanism underpinning the dynamic characteristics of saturated loess, dynamic triaxial tests were conducted on saturated loess in Xianyang City, China. The tests were performed under dynamic loads of different waveforms, confining pressures, frequencies and amplitudes. Under each dynamic load, the test included two states: one stopped after 12 loading cycles, and the other is to vibrate to the failure state. Furthermore, a scanning electron microscope test was carried out on the undisturbed samples and the sheared dynamic triaxial samples. In this paper, the dynamic elastic modulus of samples is used to represent the dynamic characteristics, and parameters such as the diameter, average abundance, average fractal dimension, and directional probability entropy of the structural units and pores are selected to describe the microstructural characteristics of samples. The results show that the dynamic elastic modulus of samples decreases with increasing number of loading cycles or axial strain and finally stabilises when different types of dynamic loads are applied. The types of dynamic loads exert a significant influence on the microstructural parameters of structural units and pores. [ABSTRACT FROM AUTHOR]

Gel permeation chromatography (GPC) is commonly used to study the aging and rejuvenation behaviours of asphalt binders, as the sizes of molecules and microstructures in asphalt binders change in such processes. The filtration procedure in preparing GPC specimens, however, may filter out some large-size microstructures in asphalt, making the measured molecular size distribution biased. To investigate this issue, two laboratory-aged asphalt binders and seven recovered ones were studied. Substances filtered from asphalt binders were analysed gravimetrically, followed by examinations using scanning electron microscope (SEM) and scanning transmission electron microscope (STEM). Relationships between binders' rheological properties and the proportion of large molecular size (LMS) content based on the GPC chromatogram were investigated before and after counting the filtered substances. Results show that microstructures in the recovered asphalt binders differ from those in laboratory-aged ones in both size and morphology. While about 1% of laboratory-aged asphalt binders is obstructed by the GPC filter, 6–10% of recovered ones are blocked. Adding the filtered substances results in better correlations between the rheological properties and the proportion of LMS content. Therefore, in using GPC to analyze aged asphalt binders, it is recommended to count the filtered substances as part of LMS content. [ABSTRACT FROM AUTHOR]

In order to solve the problem that separating zeolite 4A from solutions, we have synthesized Fe3O4/zeolite 4A magnetic nanocomposite by hydrothermal method. It is characterized by Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), Vibrating Sample Magnetometer (VSM), scanning electron microscope (SEM) and Brunner-Emmet-teller (BET). The XRD result shows that Fe3O4/zeolite 4A magnetic nanocomposite has a good crystal structure. It also shows that Fe3O4/zeolite 4A magnetic nanocomposite contains two phases of zeolite 4A and Fe3O4 MNP. The optimal sample (Z-2) was judged by the calculation of crystallinity. The successful combination of zeolite 4A and Fe3O4 MNP was visually observed through SEM technology. The functional groups of Fe3O4/zeolite 4A magnetic nanocomposite were characterized by FTIR technology. The TEM result shows that some Fe3O4 MNPs enter zeolite 4A, which further clarifies the microstructure of Fe3O4/zeolite 4A magnetic nanocomposite. N2 adsorption-desorption technique confirms that Fe3O4/zeolite 4A magnetic nanocomposite SBET is 55.3374 m2/g and Dave is 9.7128 nm. VSM result shows that Fe3O4/zeolite 4A magnetic nanocomposite magnetization is 18.4534 emu/g. Simulation experiment shows that Fe3O4/zeolite 4A magnetic nanocomposite exhibit a fast response to an external magnetic field. [ABSTRACT FROM AUTHOR]

The polycrystalline sample (Ba0.05Bi0.95)(Fe0.95Zr0.05)O3 was prepared by solid state reaction method at 850 °C. The crystal structure and surface morphology of the sample were obtained by using X-ray diffractometer and a scanning electron microscope respectively. The frequency dependence of electrical parameters using impedance spectroscopy provides the dielectric behavior and grain and grain boundary effect toward resistance and capacitance of the sample. The conduction mechanism of the sample was studied from frequency dependent ac conductivity. The ferroelectricity of the sample was studied by p-E loop at room temperature. The slope from J–E characteristics was found to be nearly equal to 1. [ABSTRACT FROM AUTHOR]

Mechanical characteristics and tribological behavior of aluminum (Al6063) matrix composites (AMCs), fabricated using different compositions of SiC particles and mixed rare earth particulates (REP) were investigated. The hybrid composites samples were fabricated via bottom pouring casting route by varying 3, 6, and 9 wt.% of SiC and 1, 2, and 3 wt.% REP(CeO2+La2O3) mixture. Microstructural examination was conducted using electron back scattered diffraction (EBSD) and scanning electron microscope (SEM) analysis. Also the elemental composition of the samples was determined by using energy dispersive spectroscopy (EDS). The microstructural studies revealed uniform dispersion of REP (CeO2+La2O3) throughout the Al6063 matrix which promotes grain refinement. Mechanical properties such as micro-hardness, impact strength, ultimate tensile strength, percentage elongation, along with tribological properties such as wear rate were investigated on AMCs at room temperature. The outcomes concluded that incorporation of up to 2 wt.% of REP mixture resulted in superior hardness, impact strength, tensile strength and lower wear rate along with marginal improvement in percentage elongation. However, a decrement in mechanical properties and specific wear rate was observed on increasing the REP mixture to 3 wt.%. [ABSTRACT FROM AUTHOR]

The effects of Mg on microstructure, defects and properties of Al–Si alloy deposited by Wire and Arc-based Additive Manufacturing (WAAM) were investigated. The WAAM alloys were characterised by the metallographic microscope, X-ray diffraction, scanning electron microscope, computed tomography and electronic universal testing machine. The results show that the secondary dendrite arm spacing (SDAS) and hydrogen content of as-deposited WAAM alloy increase, and the tendency of pore formation increases with an increase in Mg content. The impurity Fe in the WAAM alloy with low Mg content is mainly in β-Fe phase, while with high Mg content is mainly in the π-Fe phase. After solution treating and ageing treatment (T6 heat-treat), the microstructure of WAAM alloy tends to be uniform. With the increase of Mg content, the size of eutectic silicon particles increases gradually. Furthermore, the UTS and YS of the alloys increased, and the elongation decreased. [ABSTRACT FROM AUTHOR]

The freeze–thaw damage, particularly in cold region, occurs frequently when concrete structures lose their durability. In this study, the dynamic mechanical properties of concrete after 0, 50, 100, 150 cycles of freeze–thaw are investigated. The microstructure of concrete associated with freeze–thaw damage is observed by mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) technologies. According to the experimental data, the influences of the freeze–thaw cycles and the loading rate on the dynamic mechanical properties are analysed, respectively. It is shown that the apparent dynamic splitting tensile strength and the apparent dynamic fracture toughness of the specimen both decrease with the increase of the freeze–thaw cycles and the loading rate. On the basis of MIP results, it is found that the porosity, the most probable pore size and the critical diameter of the concrete all increase with the increase of the cycles of freeze–thaw. The micrographs obtained from SEM illustrate that the development of cracks and the production of crystals are dominant performances reflecting the damage of concrete under freeze–thaw cycles. In addition, the freeze–thaw cycles can induce dissolution of the specimen, which benefits the growth of the crystal ettringite. [ABSTRACT FROM AUTHOR]

In this study, three different types of stainless steels, AISI 304, AISI 420, and AISI 430 were pack borided under 850 °C–925 °C–1000 °C for 2, 4, and 6 h, respectively. Morphologies of coating were investigated by optical and scanning electron microscope (SEM). The maximum layer hardness was determined to be 1736 HV0.05, 1659 HV0.05, and 1572 HV0.05 for AISI 304, AISI 420, and AISI 430, respectively. Phases formed on the layer were determined by X-ray analysis (XRD) to confirm the presence of FeB, Fe2B, CrB, and MnB phases. Boride layer morphology was found to be a planar and compact structure. The activation energies of the coating were investigated. The corrosion resistance values of stainless steels were determined from the static immersion tests performed in 10% HCl solution. There was a remarkable increase in the corrosion resistance of borided steel compared to that of untreated samples. [ABSTRACT FROM AUTHOR]

Supersaturated carbon alloying layer was prepared on the surface of 15-5PH stainless steel using laser surface alloying technology with carbon powders as alloying materials. XRD, optical microscope, scanning electron microscope, microhardness test and wear test were performed to characterize the microstructure and wear resistance of substrate and alloying layer. Results showed that the alloying layer was rapidly solidified dendritic structure with phase compositions of high-carbon austenite and a small amount of martensite and M7C3 carbides. Microhardness of the alloying layer reached about 510 HV, which was 38.7% higher than that of the as-deposited substrate (375 HV). Carbon supersaturated solid solution strengthening and microstructure refinement strengthening were the main reasons for a substantial increase in alloying layer microhardness. After direct aging treatment, microhardness of the alloying layer further increased to nearly 640 HV. Wear test results showed that the mass loss of the aging alloying layer was about 60% lower than that of the aging substrate, which meant significantly improvement of wear resistance. [ABSTRACT FROM AUTHOR]

Al85Ni8Y4Ce3 amorphous coatings were prepared on Q235 steel by laser thermal spraying and laser remelting. The structure and thermodynamic behaviour of the coating were analysed by scanning electron microscope, energy-dispersive spectrometer, X-ray diffractometer and differential scanning calorimeter. The microhardness distribution and wear properties of the coating were investigated by microhardness tester and wear tester. The results revealed that a small number of pores and AlFeNi crystal phases presented on the surface of spraying coating, and the remelting layer presented a dense structure with a smooth surface. The volume fraction of the amorphous phase in the remelting layer was 89.9% that indicated a better glass-forming ability. The surface microhardness of the spraying coating was 754.2 HV0.2, and the hardness of the remelted layer was 847.6 HV0.2. After laser remelting treatment, the friction coefficient of the coating decreases by 20% and the wear resistance increases by 31%. [ABSTRACT FROM AUTHOR]

In this work, the effect of Cr3C2 on the microstructure and properties of 310 coatings by plasma transfer arc welding was studied. The microstructure, composition, hardness and wear resistance of the coatings were analyzed by scanning electron microscope, EDS, X-ray diffractometer, microhardness tester and friction wear tester. The results show that when Cr3C2 is less, the coating is composed of columnar crystal and cellular crystal, mainly including (Fe, Ni) Fe3Ni2FeCr0.29Ni0.16C0.06Cr2Fe14C and CrFe7C0.45. With the increase of Cr3C2, the structure becomes dendrites and new phases Cr7C3 and Cr23C6 appeared. However, the crystallinity of 5% is poor and there is no obvious grain structure. The hardness of the coatings increases first and then decreases with the content of Cr3C2. The hardness with the content of 3% is the highest. The friction coefficient corresponds to the hardness and the main wear mechanism is abrasive wear and oxidation wear. [ABSTRACT FROM AUTHOR]

A comparative study to assess the abrasive wear performance of steels for concrete mixing drum, coiled at different temperatures, was conducted by MLS-225 wet sand/rubber wheel abrasion wear tester. The microstructures and mechanical properties of tested steels before and after wear tests were examined by the optical and scanning electron microscopes, electron backscatter diffraction, Vickers hardness tester and so on. The results showed that with decreasing coiling temperatures, the strength and hardness of tested steels increased, and the wear rate decreased. The complex microstructure obtained by coiling at 150°C, mainly composed of ferrite and tempered martensite, had the best wear resistance. The main wear mechanisms of all the tested steels are microcutting and microploughing, and the initiation and propagation of cracks can be considered as a submechanism of wear. [ABSTRACT FROM AUTHOR]

In this research, the formation mechanism of platinum-modified (Pt-modified) aluminide coating structure applied by out-of-the-pack aluminizing is investigated. For this purpose, the samples of superalloy were coated with 7.5 µm platinum prepared by electroplating. Then, they were heat-treated at 1080°C for 1 h in the vacuum (10−4 torr). The platinum-coated samples were aluminized using an out-of-the-pack single-step aluminizing process at 1050°C under different times and with fixed powder composition. Afterwards, the microstructures of the coatings were evaluated using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and an X-ray diffraction (XRD). The results showed that Pt-modified aluminide coating was formed at first by the inward diffusion of Al and, then, by outward diffusion of Ni. The final coating microstructure consisted of three main layers. The outermost layer of PtAl2 precipitates in a β-Ni(Pt, Al) matrix, the middle layer of Ni-rich β-Ni(Pt, Al) and the innermost layer of interdiffusion zone. [ABSTRACT FROM AUTHOR]

In this paper, the effect of rice husk ash (RHA), as silicate impurities, on the microstructure and mechanical properties of calcium aluminate cement concrete (CACC) is explored. Various mechanical tests, including tests for obtaining the compressive, splitting tensile, flexural strengths and elastic modulus, were performed on different mixture designs containing different volume percentages of RHA (0, 2.5, 5, 7.5, and 10%) at W/Cs of 0.4 and 0.5. Furthermore, the impact of RHA on the microstructure of this concrete was examined through careful analysis of the scanning electron microscope (SEM) images and energy dispersive X-ray spectroscopy (EDS) results. The results demonstrate that, At W/C of 0.5, the microstructure and mechanical properties were improved, with the greatest improvement for the RHA substitution percentage of 5%. However, at W/C of 0.4, the addition of RHA showed no positive effect, which can be attributed to a higher specific surface area of RHA than cement. [ABSTRACT FROM AUTHOR]

In this study, an investigation was performed of the preparation of nickel nanothorn particles by the hydrothermal synthesis method. The effects of parameters were investigated on the particle shape and size, which were determined by scanning electron microscope (SEM) analysis. The synthesis parameters were hydrazine concentration, heating temperature in autoclave, heating time in autoclave, nickel sulfate concentration, pH, NaCl concentration. The phases contained in the synthesized samples were analyzed by X-ray powder diffraction (XRD) analysis, nickel purity of samples were analyzed by X-ray fluorescence (XRF), and the magnetic properties of the nickel particles were measured by a magnetic hysteresis test. The results showed that nickel nanothorn particles were successfully produced without any surfactant by simple hydrothermal synthesis. As the hydrazine concentration was increased, the thorn length of the nickel particles also increased. [ABSTRACT FROM AUTHOR]

Permeable pavements are engineered to temporarily store water to reduce flooding during rainfall events. Permeable pavements are distinguished primarily based on their surface materials which can vary from concrete, asphalt, clay brick, concrete pavers or plastic grids. This paper examined the effect of lightweight carbon-negative aggregates (CNA) on the behaviour of concrete intended for use as solid concrete block pavers in permeable pavements. Performance indicators targeted compressive strength, splitting tensile strength, density and water absorption. CNA were produced and sourced from manufacturing firm Carbon8 Systems in Kent U.K which applies patented accelerated carbonation technology to solidify incinerated ash into useful eco-friendly aggregates. The methodology involved substituting natural aggregates (NA) by mass, with CNA at percentages varying from 0 to 100. A scanning electron microscope was used to examine the aggregate–mortar interface. Both the compressive and tensile strengths decreased exponentially with the addition of CNA. Average 28-day compressive and splitting tensile strengths ranged from 69 MPa (10,000 PSI) to 18 MPa (2600 PSI) and 3.84 MPa (560 PSI) to 1.23 MPa (178 PSI) respectively. Density values decreased linearly with the addtion of CNA with average values ranging from 2200–2600 kg/m3. ⁠Conversely, water absorption increased with increases in CNA with average values ranging from 1.66% to 9.17%. Depending on the loading requirements, CNA can replace NA in solid permeable pavement blocks by up to 100%. [ABSTRACT FROM AUTHOR]

The composite coating was fabricated by laser cladding on Q235 mild steel. The cross-section morphology, microstructure, phase, micro-hardness and wear resistance of the coating were investigated by scanning electron microscope, energy dispersive spectrometry, X-ray diffraction, Vickers micro-hardness tester and dry sliding wear testing machine, respectively. Results showed that composite coating was gained without cracks and bonded with substrate excellently because of the prominent metallurgical bonding. The composite coating was made up of Ni3Ti, Cr2Ti, Ni–Cr–Fe, TiB2 and TiC. Ceramic reinforcements existed in coating with eutectic and independent structures. The micro-hardness of coating was about 5 times the substrate. Compared with substrate, the coating showed superior wear resistance. [ABSTRACT FROM AUTHOR]

A coating containing WC was prepared by induction cladding, laser cladding and plasma powder surfacing. The microstructure, chemical composition, hardness and corrosion resistance were analysed by optical microscope, scanning electron microscope, EDS, X-ray diffraction, micro hardness tester and electrochemical workstation. The results show that the forming quality of the samples deposited by induction cladding is very poor. The microstructures of LC and PS are mainly composed of dendrites, cellular crystals and interdendritic eutectic structure. Both of them contain Fe3C and Cr3C2 phase, as well as W2C phase. In addition, the PS alloy layer also contains other complex alloy phases and hard phases. The hardness decreases with the increase of current, while the hardness of laser cladding alloy layer is similar to that of plasma sample with 150A current. The best corrosion resistance is plasma sample with 125A current. The corrosion resistance of laser cladding sample is between 150A and 175A plasma sample. [ABSTRACT FROM AUTHOR]

The 0-3 connectivity lead-free barium calcium stannate titanate (BCTS)-Portland cement (PC) composites were produced by pressing and curing techniques. The effect of BCTS ceramic content on microstructure and dielectric properties of composites were studied. Scanning electron microscope images at the interfacial zone of composites showed denser microstructure between Portland cement matrix and BCTS ceramic. The dielectric constant and dielectric loss of BCTS-Portland cement composites were also found to depend on the frequency in the range tested. The dielectric results indicate that the BCTS ceramic can improve the dielectric constant (lower dielectric loss) in composites. The dielectric constant followed the cube model. [ABSTRACT FROM AUTHOR]

The hot rolled 7075 aluminum alloy was modified by friction stir processing (FSP) technology, and the effects of different processing parameters on impact toughness and microstructure of machining region were analyzed. The results showed that the impact toughness of machining region was 2.3 times that of the base metal when the rotation velocity was 1200 r/min and the feed rate was 60 mm/min, which much higher than base metal. The fracture morphology was observed by using scanning electron microscope and found that the morphology of fracture dimple was uniform and smooth. The grains in the weld nugget zone were obviously refined after friction stir processing, and the grain refinement effects were not the same in different processing parameters. [ABSTRACT FROM AUTHOR]

In this paper, a substrate material (AA5754) was coated using a consumable rod/coating shaft (AA7075) as both a single layer and gradient layers by friction stir process. The order of the gradient coating process can be listed as; mixing the Al + TiC powders, pressing inside the consumable rod, sintering at certain temperatures and coating the substrate material surface with three overlapping layers at different reinforcement ratios. Microhardness and wear tests were performed to investigate the mechanical properties of the coatings. The microstructures of the coated materials have been examined by using optical microscope and SEM. The EDX and XRD analyses were also applied to the new-coated materials. The shaft rotational speed had a significant effect on the microstructure in the friction coating which was performed at single layer and in a powder-free fashion. The gradient ratio in gradient coatings had a considerable effect on the hardness and wear resistance. [ABSTRACT FROM AUTHOR]

The microstructural evolution of an overaged Cu-4wt-%Ti alloy associated with surface mechanical attrition treatment (SMAT) has been studied by X-ray diffraction, scanning electron microscope and transmission electron microscopy. The results show that β-Cu4Ti precipitates in the topmost surface layer were dissolved after SMAT, and Cu solid solution phase with a fine grain size of approximately 25 nm was observed. Dislocation activities were the main deformation mechanism of lamellar structure in the overaged Cu–4wt-%Ti alloy. The twinning in lamellar Cu phase was inhibited by the β-Cu4Ti precipitates. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of the Mg–3Sn–2Al–1Zn (TAZ321) alloy extruded at 180–250°C and at a ram speed of 0.08 mm/s were investigated by optical microscope, X-ray diffraction, scanning electron microscope, transmission electron microscope, tensile testing and microhardness tester. The results indicate that the as-extruded alloy shows ultrafine dynamic recrystallisation grains, nanoscale Mg2Sn precipitates of 50–80 nm, strong texture and excellent mechanical properties, the degree of which mainly depends on the extrusion temperature. The tensile yield strength and elongation vary from 413 MPa and 6.7% of TAZ321 extruded at 180°C to 312 MPa and 14.1% of TAZ321 extruded at 250°C, which can be regulated flexibly. [ABSTRACT FROM AUTHOR]

As-cast transformation-induced plasticity (TRIP) steels with two different aluminium contents (2.80 and 6.75 wt-%) were subjected to investigate the effect of aluminium content on the tensile strength and hot ductility. As the Al content increases from 2.80 to 6.75 wt-%, the third brittle zone of the steel is shifted from 950–750°C to 800–750°C. The 6.75 wt-% Al-TRIP steel is a typical δ-TRIP steel that contains 44.5 wt-% δ-ferrite compared with no δ-ferrite in the 2.80 wt-% Al-TRIP steel. The solidification behaviour of these two types of TRIP steel was compared by calculating equilibrium phase diagrams. The 6.75 wt-% Al-TRIP steel was found to have better ductility than the 2.80 wt-% Al-TRIP steel below 1100°C. [ABSTRACT FROM AUTHOR]

Recent studies indicated that precipitation-hardened high-entropy alloys (HEAs) possess outstanding properties. It is difficult to obtain substantial precipitated particles for HEAs at the as-cast condition. In this paper, cast precipitation-hardened high-entropy superalloys (HESAs) Ni48−xCo18Cr10.5Fe9.3Al9.7Ti4.5Mox (at.-%, x = 1, 2, 3) were designed and prepared. All HESAs possess a high-entropy matrix and a fine γ′ particles structure. HESAs have higher ultimate tensile strength and elongation at room temperature than conventional Ni-based superalloys and close yield strength. All HESAs possess high compressive strength at elevated temperature. At 850 °C, the strengths of all alloys are higher than 800 MPa. Solid solution strengthening and precipitation strengthening were discussed. Precipitation strengthening has the greatest contribution to yield strength. [ABSTRACT FROM AUTHOR]

In order to acquire high entropy alloy (HEA) coatings with outstanding thermal stability, FeCrNiMnMoxSi0.5B0.5(x = 0, 0.8, 1.0) HEA coatings were prepared on Q235 steel by the laser cladding technique. The phase structure, microstructure and microhardness of the HEAs were carefully investigated by a scanning electron microscope (SEM), X-ray diffraction (XRD) method and a microhardness tester, respectively. The experimental results show that FeCrNiMnMoxSi0.5B0.5(x = 0, 0.8, 1.0) HEAs consist mainly of face-centred-cubic (FCC) solid solution plus a few FeMoSi phases, the microstructure evolves from wheat-shaped dendrite to net-like dendrite with the addition of Mo element. The microhardness of as-cladded coatings increases with the addition of Mo content, especially the FeCrNiMnMo1Si0.5B0.5 coating. However, the microhardness change of annealed coatings is closely related to the number of intermetallic compounds and lattice distortion intensity of FCC solid solution. [ABSTRACT FROM AUTHOR]

The ceramic oxide Na2Pb2Gd2W2Ti4Ta4O30 (NPGWT) was synthesized by the solid solution route. The formation of compound was checked by using X-ray diffraction and scanning electron microscope study. It is observed from both the studies that the material is a single phase and highly dense. The preliminary temperature variation of the dielectric study reveals ferroelectric to paraelectric phase transition much above the room temperature. The polarization study of the material further confirms the presence of ferroelectricity in the studied compound. The transport property of the material was carried out by using the impedance spectroscopy technique. From both impedance and modulus analysis, it is confirmed that conduction mechanism in the material is due to the hopping motion of charge carrier. To strengthen the hopping motion of charge carrier in the material frequency dependence, ac conductivity is carried out. [ABSTRACT FROM AUTHOR]

A continuous solid/liquid bonding method was successfully developed to fabricate Cu–10wt-%Ni–1wt-%Fe (nickel bronze) clad steel with a good metallurgical bonding in the present study. The results indicated that the diffusion distance of interface is about 1.90–2.18 µm. The average tensile shear strength of centre composite strip at as-cast state is 228 ± 5 MPa, while that of edge is 202 ± 6 MPa, and the interface strength is higher than that of bronze since the fracture always occurs on the nickel bronze side. After the rolling process, the tensile shear strength increases with the increasing rolling reduction. The reason can be ascribed to the strengthening of the nickel bronze whose strength is still lower than the interface. [ABSTRACT FROM AUTHOR]

A novel porous nickel–copper composite was designed and fabricated by sintering a mixture of a high-porosity open-cell copper foam plate and fine nickel powder. The microstructure of the porous nickel–copper composite was characterised by the scanning electron microscope. The effects of sintering temperature and dwelling time on the sintering shrinkage, sintered porosity, capillary performance and mechanical properties of the porous composite and monoporous sintered nickel powder were investigated experimentally. The nickel–copper composite presented significant lower sintering shrinkage, higher porosity, lower tensile strength and better capillary performance than the sintered nickel powder under all sintering conditions. The sintering temperature has more influence than the dwelling time on both the capillary performance and tensile strength of the sintered composite. [ABSTRACT FROM AUTHOR]

In order to study the effect of electrochemical dechlorination on chemically bound chloride ions in cement paste, the cement paste with Friedel's salt was prepared by aluminate cement doped with NaCl. Chemical analysis, X-ray diffraction phase analysis, and scanning electron microscope were used to compare and analyze. The results show that, at electric field, the Friedel's salt can be decomposed to cubic C3AH6, and the microstructure becomes looser; The higher voltage can make the better the dechlorination effects, but the more destructive; The destructiveness of the surrounding slurry is greater than that away from the steels. [ABSTRACT FROM AUTHOR]

40Cr steel was formed for chain wheel using a warm extrusion technique at different temperatures. The microstructures and chemical compostions of the obtained samples were analysed using an optical microscope and photoelectric direct-reading spectrometer, repectively. After the tensile test, the fracture morphologies of 40Cr steel were analysed using a field emisson scanning electron microscope, the effects of warm extrusion temperatures on the tensile properties of 40Cr steel were discussed. The results show that the yield limits of 40Cr steel extruded warmly at 550, 650, and 750°C are coincident approximately, compared with that at the extrusion temperature of 550°C, both the tensile strengths and the elongation rates of 40Cr steel at the extrusion temperatures of 650 and 750°C decrease. As the extrusion temperature increases, both the residual and the retained austenite contents of 40Cr steel decrease, and the plastic and the tensile strengths of 40Cr steel decrease. [ABSTRACT FROM AUTHOR]

In this study, to further understand the effect of microstructure on the third type strain ageing (3rd SA) phenomenon, three kinds of heat treatments were conducted on cold-rolled DH-36 structural steel. The microstructures of the heat-treated specimens were observed using scanning electron microscope and compared with the as-received microstructure. The influences of heat treatment on the 3rd SA effect were analyzed. Through the analysis of the previous experimental results of DH-36 steel and Q235B steel, stress peak in the flow stress vs. temperature curves caused by the 3rd SA effect was observed at each of the indicated strain rates for the two steels. As strain rate increases, the stress peak shifts to higher temperature range. Based on the mechanism of the 3rd SA effect, e.g. the interaction of moving dislocations and diffusing solute atoms, a model was developed to quantitatively describe the strain rate effect on the 3rd SA effect. [ABSTRACT FROM AUTHOR]

Effect of heat treatment on the recovery of microstructure and mechanical properties of a service-exposed IN939 superalloy was studied. Four-stage heat treatment was performed on the service-exposed alloy. The microstructures of the service-exposed and rejuvenated alloys were examined by optical and scanning electron microscopes. The hardness, tension, and stress-rupture tests were carried out to characterise the mechanical properties. The results showed that the heat treatment could rejuvenate the microstructure of the alloy that was deteriorated during the service at high temperatures. Decomposed MC carbides were transformed to new fine carbides, continuous M23C6 carbides were dissolved and new discontinuous carbides along the grain boundaries were regenerated and, finally, the fine γ׳ particles were reformed. The microstructural recovery resulted in an increase in the hardness and ultimate tensile strength of the alloy. The results also showed that the creep behavior of the alloy at a testing temperature of 850°C could be improved by the heat treatment. [ABSTRACT FROM AUTHOR]

This study compared the bioactive, physical and microstructural properties of blackcurrant powders prepared by an innovative fluidized-bed jet milling and drying method (FBJD) with those obtained by freeze drying (FD), convective drying (CD) and spray drying (SD). Bioactives such as vitamin C and anthocyanins were measured by HPLC, while antioxidant activity and total content of polyphenols were measured spectrophotometrically. A scanning electron microscope was used to establish the microstructure of both fresh fruits and powders. Water activity, water-holding capacity, water solubility index and pH were also determined. Retention of total polyphenols and vitamin C in FBJD powders was 88% and 79%, respectively, and 80% for both polyphenols and vitamin C in FD powders. Taking the above into account the FBJD method was found to be comparable to the FD method and compared favorably against the commonly used CD and SD methods. [ABSTRACT FROM AUTHOR]