Effect of Ti-Mo-V composite addition on microstructure andmechanical properties of marine 10Ni5CrMoV steel

The effects of Ti-Mo-V composite addition on the evolution of precipitates in marine 10Ni5CrMoV steel andthe corresponding strength and toughness mechanisms were systematically investigated.Ti-Mo-V composite addition canform the Ti_(x)Mo_(y)V_(z)C carbide with TiC as core and Mo-V as shell in the order of Ti(C)→V→Mo.The yield strength of thespecimens is increased from 815 MPa to 876 MPa due to the nanoscale precipitates enhancing the pinning effect on grainboundaries and dislocations,and the contribution of precipitation and dislocation strengthening is increased.The decrease of ductile-brittle transition temperature from−103 to−116℃is attributed to the decrease in equivalent grainsize and the increase of high-angle grain boundary misorientation,which hinders the initiation and propagation of cracks.When the mass fraction of Ti is 0.05%,the strength and cryogenic toughness can be improved synergistically,which alsoprovides a theoretical basis and experimental reference for exploring the more excellent combination of strength andcryogenic toughness of marine 10Ni5CrMoV steel.

Heterogeneous catalytic activation of peroxymonosulfate for efficient degradation of organic pollutants by magnetic Cu^0/Fe_3O_4 submicron composites

Magnetic Cu^0/Fe3O4 submicron composites were prepared using a hydrothermal method and used as heterogeneous catalysts for the activation of peroxymonosulfate（PMS） and the degradation of organic pollutants.The as-prepared magnetic Cu^0/Fe3O4 submicron composites were composed of Cu^0 and Fe3O4 crystals and had an average size of approximately 220 nm.The Cu^0/Fe3O4 composites could efficiently catalyze the activation of PMS to generate singlet oxygen,and thus induced the rapid degradation of rhodamine B,methylene blue,orange Ⅱ,phenol and 4-chlorophenol.The use of0.1 g/L of the Cu^0/Fe3O4 composites induced the complete removal of rhodamine B（20 μmol/L） in15 min,methylene blue（20 μmol/L） in 5 min,orange Ⅱ（20 μmol/L） in 10 min,phenol（0.1mmol/L） in 30 min and 4-chlorophenol（0.1 mmol/L） in 15 min with an initial pH value of 7.0 and a PMS concentration of 0.5 mmol/L.The total organic carbon（TOC） removal higher than 85%for all of these five pollutants was obtained in 30 min when the PMS concentration was 2.5 mmol/L.The rate of degradation was considerably higher than that obtained with Cu^0 or Fe3O4 particles alone.The enhanced catalytic activity of the Cu^0/Fe3O4 composites in the activation of PMS was attributed to the synergistic effect of the Cu^0 and Fe3O4 crystals in the composites.Singlet oxygen was identified as the primary reactive oxygen species responsible for pollutant degradation by electron spin resonance and radical quenching experiments.A possible mechanism for the activation of PMS by Cu^0/Fe3O4 composites is proposed as electron transfer from the organic pollutants to PMS induces the activation of PMS to generate ^1O2,which induces the degradation of the organic pollutants.As a magnetic catalyst,the Cu^0/Fe3O4 composites were easily recovered by magnetic separation,and exhibited excellent stability over five successive degradation cycles.The present study provides a facile and green heterogeneous catalysis method for the oxidative removal of organic pollutants.

Non-isothermal reduction kinetics of Fe_2O_3-NiO composites for formation of Fe-Ni alloy using carbon monoxide

The non-isothermal reduction kinetics and mechanism of Fe2O3-NiO composites with different Fe2O3-NiO compacts using carbon monoxide as reductant were investigated. The results show that the reduction degree increases rapidly with increasing the content of NiO, and the presence of NiO also improves the reduction rate of iron oxides. It is found that NiO is preferentially reduced at the beginning of the reactions, and then the metallic Ni acts as a catalyst promoting the reduction rate of iron oxides. It is also observed that the increase of the Ni O content enhances the formation of awaruite(FeNi3) but decreases the percentage of kamacite(Fe,Ni) and taenite(Fe,Ni). The particle size of the materials tends to be uniform during the reduction process due to the presence of metallic nickel, metallic iron and the formation of Fe-Ni alloy. The concentration of CO in the product gas is greater than that of CO2 at the beginning of the reaction and then slows down. The fastest reduction rate of Fe2O3-NiO composites with CO appears at 400-500 °C, and nucleation growth model can be used to elucidate the reduction mechanism. Nucleation growth process is found to be the rate controlling step when the temperature is lower than 1000 °C.

Effects of intermediate Ni layer on mechanical properties of Al–Cu layered composites fabricated through cold roll bonding

Layered composites have attracted considerable interest in the recent literature on metal composites. Their mechanical properties depend on the quality of the bonding provided by the intermediate layers. In this study, we analyzed the mechanical properties and bond strengths provided by the nickel layer with respect to its thickness and nature(either powder or coating). The results suggest that bond strength decreases with an increase in the content of nickel powder. At 0.3 vol% of nickel coating, we found the nature of nickel to be less efficient in terms of bond strength. A different picture arose when the content of nickel was increased and the bond strength increased in nickel coated samples. In addition, the results demonstrate that mechanical properties such as bend strength are strongly dependent on bond strength.

Effects of addition of rare earth on properties and structures of Ni-W-B-SiC composite coatings

The effects of rare earth (RE) on the composition, phase structures, surface morphologies and hardness of electrodeposited RE Ni W B SiC composite coatings were discussed. The results show that W and SiC contents in the coatings increase with the increase of RE in the bath. When RE is added in the coatings, the grains are refined and the trend of formation of amorphous coatings is increased. Moreover, the thermal stability of the RE Ni W B SiC composite coatings is enhanced. The hardness of the coatings is increased with the increase of heat treatment temperature, and it reaches the peak value when heated at 400 ℃. Besides, the hardness of the RE Ni W B SiC coatings is higher than that of the Ni W B SiC coatings.

Erosive Wear and Wear Mechanism of in situ TiC_P/Fe Composites

The base structure of in situ TiCp/Fe composites fabricated under industrial condition was changed by different heat treatments. Erosive wear tests were carried out and the results were compared with that of wear-resistant white cast iron. The results suggest that the wear resistance of the in situ TiCp/Fe composite is higher than that of wear-resistant white cast iron under the sand erosive wear condition. The wear mechanism of the wear-resistant white cast iron was a cycle process that base surface was worn and carbides were exposed, then carbides was broken and wear pits appeared. While the wear mechanism of in situ TiCp/Fe composite was a cycle process that base surface was worn and TiC grains were exposed and dropped. The wear resistance of in situ TiCp/Fe composite was lower than that of wear-resistant white cast iron under the slurry erosive wear condition. Under such circumstance, the material was not only undergone erosive wear but also electrochemistry erosion due to the contact with water in the medium. The wear behaviours can be a combination of two kinds of wear and the sand erosive wear is worse than slurry erosive wear.

Microstructure,tribological behavior and magnetic properties of Fe−Ni−TiO_(2) composite coatings synthesized via pulse frequency variation

The Fe−Ni−TiO_(2) nanocomposite coatings were electrodeposited by pulse frequency variation.The results showed that the nanocomposite with a very dense coating surface and a nanocrystalline structure was produced at higher frequencies.By increasing the pulse frequency from 10 to 500 Hz,the iron and TiO_(2) nanoparticles contents were increased in expense of nickel content.XRD patterns showed that by increasing the frequency to 500 Hz,an enhancement of BCC phase was observed and the grain size of deposits was reduced to 35 nm.The microhardness and the surface roughness were increased to 647 HV and 125 nm at 500 Hz due to the grain size reduction and higher incorporation of TiO_(2) nanoparticles into the Fe−Ni matrix(5.13 wt.%).Moreover,the friction coefficient and wear rate values were decreased by increasing the pulse frequency;while the saturation magnetization and coercivity values of the composite deposits were increased.

Improving Densification and Mechanical Properties of FeAl/TiC Composites by Addition of Ni

FeAl/TiC composites were fabricated by hot pressing blended elemental powders. The effects of Ni-doping on thedensification and mechanical properties of the composites were studied. Results show that the density of the composites decreases with the content of TiC increasing, and the addition of Ni significantly improves the densificationprocess by enhancing mass transfer in the bonding phase. The mechanical properties of the composites are closelyrelated with their porosity. Besides increasing the density of the composites, the addition of Ni improves the mechanical properties by other three effects: solution-strengthening the bonding phase, strengthening the FeAI-TiC interfaceand increasing ductile fracture in FeAl phase.

Mechanical properties and wear resistance of medium entropy Fe40Mn40Cr10Co10/TiC composites

The Fe40Mn40Cr10Co10/TiC (volume fraction of TiC, 10%) composites were synthesized in combination of ball milling and spark plasma sintering (SPS) in the present work. Mechanical properties and wear resistance of the Fe40Mn40Cr10Co10/TiC composites were individually investigated. It was found that TiC particles homogenously distributed in the Fe40Mn40Cr10Co10/TiC composite after being sintered at 1373 K for 15 min. Meanwhile, grain refinement was observed in the as-sintered composite. Compared with the pure Fe40Mn40Cr10Co10 medium entropy alloy (MEA) matrix grain, addition of 10% TiC particles resulted in an increase in the compressive strength from 1.571 to 2.174 GPa, and the hardness from HV 320 to HV 872. Wear resistance results demonstrated that the friction coefficient, wear depth and width of the composite decreased in comparison with the Fe40Mn40Cr10Co10 MEA matrix. Excellent mechanical properties and wear resistance could offer the Fe40Mn40Cr10Co10/TiC composite a very promising candidate for engineering applications.

Structure and characteristics of electrodeposited RE-Ni-W-P-B_4C-PTFE composite coatings

Hardness, friction and wear characteristics of electrodeposited RE Ni W P B 4C PTFE composite coatings were studied, and the reason for these fine characteristics was explained in respect of structure. The results show that 1) the structure of RE Ni W P B 4C PTFE composite coatings experiences a transformation process from amorphous to mixture then to crystal as the heat treatment temperature rises; 2) incorporating of B 4C greatly increases the hardness of the coating; 3) the wear resistance of the coating is best with heat treatment for 1?h at 300?℃, which is greatly superior to that of the other traditional coatings.

Fabrication and Microwave Absorption Properties of Fe_(0.64)Ni_(0.36)-NiFe_2O_4 Nanocomposite

Fe_(0.64)Ni_(0.36)-NiFe_2O_4 nanocomposite was performed with partially reducing NiFe_2O_4 nanoparticles in Ar/H_2 ambient.The microwave and static magnetic properties were investigated.The results showed that the nanocomposite was characterized with enhanced microwave absorption properties.The optimal reflection loss(RL)of the nanocomposite reached-24.8 dB at 14 GHz for an absorber thickness of 1.5 mm.Meanwhile,a broad bandwidth for RL<-10 dB was obtained in the range of 3.1—15.1 GHz for an absorber thickness from1.0 to 4.0 mm.The enhancement is attributed to the increase of dielectric and magnetic loss after reducing procedure.

Effect of Counterface Material on Friction and Wear Behavior of Ni-Cr-W-Al-Ti-MoS_2 Composites

Ni-Cr-W-Al-Ti-MoS2 self-lubricating composites were prepared through the powder metallurgy （P/M） method. Their friction properties were investigated by a pin-on-disk tribometer in the range from the room temperature to 600 ℃. Alumina, silicon nitride and nickel-iron-sulfide alloys were selected as the counterface materials. Results indicate that the lowest friction coefficients under 0.22 can be obtained at 600℃ when rubbed against alumina. When rubbed against nickel-iron-sulfide alloys, are presented the lowest wear rates in the magnitude of 10^-6 mm^3/N-m, one order of magnitude lower than those when rubbed against ceramics. In the case of three rubbing pairs, the wear rates of the composite containing MoS2 present themselves inversely proportional to friction coefficients. With alumina ceramics used as a counterface, transfer films and glaze layers will form on the contact surface playing a main role in lubrication at high temperatures. However, when silicon nitride and nickel-iron-sulfide alloy are used, the lubricating transfer films appear not to be prominent.

Effect of Fe content on microstructure and mechanical properties of Cu-Fe-based composite coatings by laser induction hybrid rapid cladding

To select the proper composition and obtain an overall material?microstructure?property relationship for Cu?Fe alloy, theeffect of Fe content on microstructure and properties of Cu?Fe-based composite coatings by laser induction hybrid rapid claddingwas investigated. Microstructure characterization of the composite coatings was tested utilizing SEM, XRD and EDS. Microhardnessmeasurement was executed to evaluate the mechanical properties of the composite coatings. The results show that for low Fe content,the composite coating presents a feature that Fe-rich equiaxed dendrites are embedded in the Cu-rich matrix. With increasing Fecontent, the Fe-rich particles are dispersed in the Cu-rich matrix. With further increasing Fe content, large amounts of Cu-richparticles are homogeneously dispersed in the interdendrite of the Fe-rich matrix. Correspondingly, the average microhardness of thecomposite coatings increases gradually with the increase of Fe content and the microhardness of Cu14.5Fe83Si2C0.5 coating is muchtwice higher than that of the substrate.

Generation Mechanism of Interfacial Layer and Its Effect on Fe-Cr-Ni/Al-Si-Cu-Ni-Mg Composite Performance

Fe-Cr-Ni/Al-Si-Cu-Ni-Mg composite was taken as the experimental material. The chemical composition of interfacial layer was tested. The generation mechanism and influence of interfacial layer on the composite were analyzed. The results indicated that the generation of interfacial layer is sensitive to temperature. Interfacial layer will generate rapidly when temperature reaches 500 ℃ or above. The interfacial layer is mainly composed of Al, Si, Cu, Fe, and Cr, element Ni distributes at the outward of the interfacial layer for the precipitate of Ni later than Si and Cu, and there is almost no diffusion of Ni during the solution treatment. During heat treatment process, unequal quantity changing of metal atom results in disperse or concentrated vacancies or holes near the matrix. The existence of interfacial layer will induce a decrease of compression strength and plasticity at room temperature and an increase of strength at higher temperature comparing with composite without interfacial layer.

Fabrication and Magnetic Properties of Composite Ni_(0.5)Zn_(0.5)Fe_2O_4/Pb(Zr_(0.52)Ti_(0.48))O_3 Nanofibers by Electrospinning

One-dimensional and quasi-one-dimensional nanostructure materials are promising building blocks for electromagnetic devices and nanosystems.In this work,the composite Ni0.5Zn0.5Fe2O4（NZFO）/ Pb（Zr0.52Ti0.48）O3（PZT） nanofibers with average diameters about 65 nm are prepared by electrospinning from poly（vinyl pyrrolidone） （PVP） and metal salts.The precursor composite NZFO/PZT/PVP nanofibers and the subsequent calcined NZFO/PZT nanofibers are investigated by Fourier transform infrared spectroscopy （FT- IR） ,X-ray diffraction （XRD）,scanning electron microscopy （SEM）.The magnetic properties for nanofibers are measured by vibrating sample magnetometer（VSM）.The NZFO/PZT nanofibers obtained at calcination temperature of 900 °C for 2 h consist of the ferromagnetic spinel NZFO and ferroelectric perovskite PZT phases,which are constructed from about 37 nm NZFO and 17 nm PZT grains.The saturation magnetization of these NZFO/PZT nanofibers increases with increasing calcination temperature and contents of NZFO in the composite.

Corrosion resistance of electrodeposited RE-Ni-W-P-SiC-PTFE composite coating in phosphoric and ferric chloride

Corrosion rate and anode polarization curves of electrodeposited RE-Ni-W-P-SiC-PTFE composite coating in various concentrations of phosphoric and ferric chloride were researched. The results show that corrosion rate of the composite coatings increases with the increasing concentrations of phosphoric and ferric chloride, and reaches the maximum value when phosphoric concentration is 40% and ferric chloride concentration is 20% (mass fraction, the same below if not mentioned). Anode polarization curves of the composite coatings show that anode polarization current density of the composite coatings heat-treated at 200 ℃ or 500 ℃ is lower than that of other coatings heat-treated at 300 ℃ or 400 ℃, which displays that the composite coatings heat-treated at 200 ℃ or 500 ℃ have better corrosion resistance. Besides, corrosion resistance of the composite coating heat-treated at 500 ℃ is better than that as deposited and RE-Ni-W-P-SiC composite coating heat-treated at 400 ℃, and is also better than that of 316L stainless steel.

CYCLIC OXIDATION OF Ni-La_2O_3 COMPOSITE COATINGS ELECTRODEPOSITED ON NICKEL AND Fe26Cr STAINLESS STEEL

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Epoxy Resin/Nano Ni@C Composites Exhibiting NTC Effect with Tunable Resistivity

Epoxy resin/Ni@C nanoparticle composites with aligned microstructure were prepared by using a procedure of magnetic field assisted curing. The results show that the resistivity of composites exhibits negative temperature coefficient （NTC） effect above room temperature, and can be adjusted by varying the content filler and the magnitude of magnetic field applied. Hill＇s quantum tunneling model was modified to understand the electrical conduction mechanism in the composites. It shows that the NTC effect ascribes to the dominant thermal activated tunneling transport of electron across adjacent nanoparticles, as well as the low thermal expansivity of epoxy resin matrix.

Microstructure,mechanical properties,and wear resistance of VCp-reinforced Fe-matrix composites treated by Q&P process

A quenching and partitioning(Q&P) process was applied to vanadium carbide particle(VCp)-reinforced Fe-matrix composites(VC-Fe-MCs) to obtain a multiphase microstructure comprising VC, V8 C7, M3 C, α-Fe, and γ-Fe. The effects of the austenitizing temperature and the quenching temperature on the microstructure, mechanical properties, and wear resistance of the VC-Fe-MCs were studied. The results show that the size of the carbide became coarse and that the shape of some particles began to transform from diffused graininess into a chrysanthemum-shaped structure with increasing austenitizing temperature. The microhardness decreased with increasing austenitizing temperature but substantially increased after wear testing compared with the microhardness before wear testing; the microhardness values improved by 20.0% ± 2.5%. Retained austenite enhanced the impact toughness and promoted the transformation-induced plasticity(TRIP) effect to improve wear resistance under certain load conditions.

Structure and properties of electrodeposition RE-Ni-W-B-B_4C-PTFE composite coating

The components, surface and cross sectional morphologies, and the effects of heat treatment temperature on phase structure, hardness, abrasion resistance and oxidation resistance of pulse electrodeposition RE-Ni-W-B-B4C-PTFE composite coatings, were all investigated. The results show that W and B contents increase in the RE-Ni-W-B composite coating by using pulse electrodeposition. RE, PTFE and B4C particles can be co-deposited into the Ni-W-B composite coating, but the amount is very little. X-ray diffraction analysis displays that the RE-Ni-W-B-B4C-PTFE composite coating is mainly amorphous, partially crystallized as-deposited, but it turns into crystalline state and PTFE in the coatings will decompose after the heat treatment temperature is higher than 400℃. The hardness of the composite coating increases with increasing heat treatment temperature, it comes up to the highest value at 400℃. The oxidized film mass of the composite coating increases slowly when the oxidation temperature is lower than 500℃, but it increases linearly and sharply after the oxidation temperature is higher than 600℃.