The steady-state temperature field of horizontal core-filling continuous casting （HCFC） for producing copper cladding aluminum rods was simulated by finite element method to investigate the effects of key processing...The steady-state temperature field of horizontal core-filling continuous casting （HCFC） for producing copper cladding aluminum rods was simulated by finite element method to investigate the effects of key processing parameters on the positions of solid-liquid interfaces （SLIs） of copper and aluminum. It is found that mandrel tube length and mean withdrawing speed have significant effects on the SLI positions of both copper and aluminum. Aluminum casting temperature （TAI） （1003-1123 K） and secondary cooling water flux （600-900 L.h-1） have little effect on the SLI of copper but cause the SLI of aluminum to move 2-4 mm. When TA1 is in a range of 1043-1123 K, the liquid aluminum can fill continuously into the pre-solidified copper tube. Based on the numerical simulation, reasonable processing parameters were determined.展开更多
Co-based alloy coating was prepared on Zr alloy using laser melting and cladding technique to study the difference in the high-temperature oxidation behavior between pure metal Co coatings and Co-T800 alloy coatings,a...Co-based alloy coating was prepared on Zr alloy using laser melting and cladding technique to study the difference in the high-temperature oxidation behavior between pure metal Co coatings and Co-T800 alloy coatings,as well as the wear resistance of the coatings.Besides,the effect of changing the laser melting process on the coatings was also investigated.The oxidation mass gain at 800–1200℃and the high-temperature oxidation behavior during high-temperature treatment for 1 h of two coated Zr alloy samples were studied.Results show that the Co coating and the Co-T800 coating have better resistance against high-temperature oxidation.After oxidizing at 1000℃for 1 h,the thickness of the oxide layer of the uncoated sample was 241.0μm,whereas that of the sample with Co-based coating is only 11.8–35.5μm.The friction wear test shows that the depth of the abrasion mark of the coated sample is only 1/2 of that of the substrate,indicating that the hardness and wear resistance of the Zr substrate are greatly improved.The disadvantage of Co-based coatings is the inferior corrosion resistance in 3.5wt%NaCl solution.展开更多
A refractive index(RI)sensor based on a cladding-etched thin-core single-mode fiber(TCSMF)sandwiched between two single-mode fibers is demonstrated.The experimental results show that the sensitivity,within the RI rang...A refractive index(RI)sensor based on a cladding-etched thin-core single-mode fiber(TCSMF)sandwiched between two single-mode fibers is demonstrated.The experimental results show that the sensitivity,within the RI range of 1.333–1.340,is enhanced at least 6 times by etching.It increases with the surrounding RI and reaches 857.5 nm/RIU at RI of 1.3684,and it can be expected to be higher with the decrease of the cladding diameter of the TCSMF.展开更多
The high-entropy alloy composite coatings AlCu_(2)Ti(NiCr)_(2)-(WC)_(x)(x denotes powder feeding speeds,including 0,25,50,and 75 r/min)were prepared by plasma cladding using a hybrid mode of AlCu_(2)(NiCr)_(2)Ti cable...The high-entropy alloy composite coatings AlCu_(2)Ti(NiCr)_(2)-(WC)_(x)(x denotes powder feeding speeds,including 0,25,50,and 75 r/min)were prepared by plasma cladding using a hybrid mode of AlCu_(2)(NiCr)_(2)Ti cable-type welding wire(CWW)and tungsten carbide(WC)powder.The effect of WC powder feeding speed on the microstructure,hardness,and wear properties of the prepared coatings was investigated.The results show that the coatings consist of body-centered cubic main phases and face-centered cubic secondary phases,with carbide reinforcement phases formed due to the addition of WC.The hardness and wear resistance of the coatings are significantly improved compared to the TC11 substrate.When WC powder feeding speed is set at 50 r/min,the coating exhibits optimal wear resistance,with a minimum volume wear rate of 8.5869×10^(-6)mm^(3)·N^(-1)·m^(-1),greatly improving the wear properties of TC11 surface.The coincident CWW-powder plasma cladding provides a viable method for the preparation of highentropy alloy composite coatings with enhanced wear resistance.展开更多
Aseries of [(Fe_(0.6)Co_(0.2)Ni_(0.2))_(0.75-0.03x)B_(0.2)Si_(0.05+0.03x)]_(96)Nb_(4) amorphous alloy composite coatings were prepared by adjusting the silicon content(x=0,1,2,3,4,5,and 6)and their microstructures and...Aseries of [(Fe_(0.6)Co_(0.2)Ni_(0.2))_(0.75-0.03x)B_(0.2)Si_(0.05+0.03x)]_(96)Nb_(4) amorphous alloy composite coatings were prepared by adjusting the silicon content(x=0,1,2,3,4,5,and 6)and their microstructures and tribological properties were investigated by laser cladding technique.Additionally,the effect of Si on the glass forming ability(GFA)of the layers was understood.Results show that an appropriate Si content can refine the microstructure of the FeCoNiBSiNb laser cladding layers and improve the mechanical and tribological properties.The hardness of the coating layer increases monotonically with the Si content.At the Si content of 4.8at%(x=0),the coating layer exhibits a relatively low hardness(734.2HV 0.1).Conversely,at the silicon content of 13.44at%(x=3),the coating layer exhibits the highest hardness(1106HV 0.1).The non-crystalline content and tensile strength exhibit an initial increase,followed by a subsequent decrease.At x=2,the coating exhibits its maximum fracture strength(2880 MPa).However,when x>2,the fracture strength of the coating decreases with an increase in x.Conversely,with an increase in Si content,the wear volume loss initially decreases and then increases.At a Si content of 10.56at%(x=2),the coating exhibits the highest non-crystalline content(42%),the highest tensile strength(2880 MPa),and the most favorable dry friction performance.展开更多
The failure of mechanical components is mainly caused by three key mechanisms:wear,corrosion,and fatigue.Among these failure modes,wear of mechanical components notably increases energy consumption and leads to substa...The failure of mechanical components is mainly caused by three key mechanisms:wear,corrosion,and fatigue.Among these failure modes,wear of mechanical components notably increases energy consumption and leads to substantial economic losses.Fe-Cr-C-B-Ti-Y wear-resistant cladding metals were prepared by the plasma cladding method.The wear performance of the cladding metals was analyzed using an MLS-23 rubber wheel wet sand wear tester.X-ray diffraction,scanning electron microscope,electron backscatter diffraction,and transmission electron microscope were employed to investigate the phase composition and microstructure of the cladding metals,followed by a discussion of their strengthening and wear mechanisms.The results indicate that the microstructure of Fe-Cr-C-B-Ti-Y cladding metals is composed of austeniteγ-Fe,M_(23)(C,B)_(6)eutectic carbide,and TiC hard phase.As the Y_(2)O_(3)content increases,the hardness and wear resistance of the cladding metal show a trend of first increasing and then decreasing.When the Y_(2)O_(3)content is 0.4wt%,the precipitation of TiC hard phase and M_(23)(C,B)_(6)-type eutectic carbides reaches maximum,and the grain size is the finest.The cladding metal exhibits optimal formability,featuring the smallest wetting angle of 52.2°.Under this condition,the Rockwell hardness value of the cladding metal is 89.7 HRC,and the wear mass loss is 0.27 g.The dominant wear mechanism of cladding metals is abrasive wear,and the material removal process involves micro-cutting and plowing.展开更多
In order to enhance the wear resistance of 45 steel,a WC/Stellite 6 composite layer with 30%WC which with different morphologies(spherical and irregular)was prepared on the surface of 45 steel by laser cladding techno...In order to enhance the wear resistance of 45 steel,a WC/Stellite 6 composite layer with 30%WC which with different morphologies(spherical and irregular)was prepared on the surface of 45 steel by laser cladding technology.The effects of WC morphology on the phase composition,microstructure,microhardness,and wear resistance of the cladding layer were compared and analyzed.The res-ults show that the surface of the cladding layer was well formed.M_(23)C_(6),M_(7)C_(3),WC,and W_(2)C exist in both cladding layers.With the ad-dition of spherical WC,the diffraction peaks of γ-Co appear on the left side of the main peak of Co6W6C.The area of intergranular carbides accounts for a large proportion in the surface layer which with the fine grains.During the process of laser cladding the spherical WC particles with loose structure are prone to melting,including their interior.However,the melting amount of irregular WC particles is finite,which only occurs on the periphery of the particles,and the particle interior is relatively intact.The microhard-ness of two cladding layers gradient increases from the substrate to the surface layer.The surface layer added spherical WC has high-er microhardness,which reaches 790.6 HV1.Nevertheless,the wear resistance of the cladding layer added irregular WC is better than that of the cladding layer added spherical WC.The reason is because that the incompletely melted irregular WC particles are uni-formly distributed in the cladding layer which provided the support points for the cladding layer matrix during the wear process,the wear of the cladding layer by the grinding pair is reduced consequently.展开更多
Conventional Fe-C alloy parts used in mechanical transmission and braking systems exposed to the external environment often suffer from wear and corrosion failures.Surface coating strengthening technologies have been ...Conventional Fe-C alloy parts used in mechanical transmission and braking systems exposed to the external environment often suffer from wear and corrosion failures.Surface coating strengthening technologies have been explored to improve the surface performance and prolong service life of these parts.Among these technologies,laser cladding has shown promise in producing Fe-based alloy coatings with superior interfacial bonding properties to the Fe-C alloy substrate.Additionally,the microstructure of the Fe-based alloy coating is more uniform and the grain size is finer than that of surfacing welding,thermal spraying,and plasma cladding,and the oxide film of alloying elements on the coating surface can improve the coating performance.However,Fe-based alloy coatings produced by laser cladding typically exhibit lower hardness,lower wear resistance,corrosion resistance,and oxidation resistance compared to coatings based on Co and Ni alloys.Moreover,these coatings are susceptible to defects such as pores and cracks.To address these limitations,the incorporation of rare-earth oxides through doping in the laser cladding process has garnered significant attention.This approach has demonstrated substantial improvements in the microstructure and properties of Fe-based alloy coatings.This paper reviewed recent research on the structure and properties of laser-cladded Fe-based alloy coatings doped with various rare earth oxides,including La_(2)O_(3),CeO_(2),and Y_(2)O_(3).Specifically,it discussed the effects of rare earth oxides and their concentrations on the structure,hardness,friction,wear,corrosion,and oxidation characteristics of these coatings.Furthermore,the mechanisms by which rare earth oxides influence the coating’s structure and properties were summarized.This review aimed to serve as a valuable reference for the application and advancement of laser cladding technology for rare earth modified Fe-based alloy coatings.展开更多
Cladding light strippers(CLSs)are essential components for high-power monolithic fiber laser systems.Because they allow for bending of the fiber,which leads to an excellent stripping efficiency of light with a low ray...Cladding light strippers(CLSs)are essential components for high-power monolithic fiber laser systems.Because they allow for bending of the fiber,which leads to an excellent stripping efficiency of light with a low ray angle,refractive index-based CLSs have an advantage over the commonly used alternative approaches.However,conventional high-index CLSs overheat at relatively low input power as the maximum temperature,located in a hot-spot,increases linearly with the input power.This applies particularly to CLSs in thulium-based fiber systems,where very low power can already lead to extreme heat generation due to the high cladding material absorption around 2μm.Here,we investigate materials with a highly negative thermooptical coefficient combined with a refractive index closely above glass to distribute the stripped power and heat uniformly along an increased fiber length.Analyzing multiple CLS geometries for fiber diameters of 125 and 400μm,we show record-high maximum input powers for single-material CLSs of 21.8 W for the signal(2039 nm)and 675 W for the pump wavelength(793 nm).Transmitting excess light instead of overheating,this wavelength-adaptable self-protecting CLS concept is fast to apply onsite in the lab and reaches stripping efficiencies of>40 dB in the bent version.展开更多
In order to improve the surface properties of titanium alloys,a novel TiFeNiCuV high-entropy alloy(HEA)coating was prepared on a Ti−6Al−4V(TC4)substrate via laser cladding under different laser powers.The microstructu...In order to improve the surface properties of titanium alloys,a novel TiFeNiCuV high-entropy alloy(HEA)coating was prepared on a Ti−6Al−4V(TC4)substrate via laser cladding under different laser powers.The microstructure,microhardness,and friction wear properties of the coatings were systematically investigated.The results showed that at laser powers of 1200 and 2000 W,the microstructure of the coatings exhibited a core-shell dendritic structure.At 2800 W,the coatings displayed a daisy-like eutectic structure.The average hardness of the coatings reached HV 692.281 owing to solid-solution and fine-grain strengthening.Wear mechanisms of the coatings at room temperature primarily involved fatigue and slight oxidation wear.The total volume loss of the coatings was 4.22×10^(−3)mm^(3),which was 14.47%that of the TC4,indicating excellent wear resistance.展开更多
This work investigated tribological behavior and corrosion resistance of laser cladding(LC)Ti_(50)Nb_(15)V_(15)Zr_(5)Cr_(5)Al_(10)high-entropy alloy(HEA)coatings on Ti6Al4V substrates.Microstructural characterization ...This work investigated tribological behavior and corrosion resistance of laser cladding(LC)Ti_(50)Nb_(15)V_(15)Zr_(5)Cr_(5)Al_(10)high-entropy alloy(HEA)coatings on Ti6Al4V substrates.Microstructural characterization illustrated that there was only body centered cubic phase in the HEA coating.Besides,the coatings of different laser power all exhibited obviously higher hardness than the substrate.It is illustrated that the microstructure of the HEA coatings is composed of body centered cubic phase,and the temperature gradient contributes to the distribution difference between the equiaxed and columnar grains.Meanwhile,the relationships between the tribological behavior,corrosion resistance and alloying elements have been illustrated.The HEA coating with 2200 W holds the best wear and corrosion resistance.During the friction process,there are many oxides formed at high temperatures,and adhesive wear contributes most to the wear mechanism of the coatings.The wear volumes of the HEA coatings are only 24.7%to 45.5%of that of the Ti6Al4V substrate.Due to the alloying elements like Cr and Al,there is dense passive film formed during the corrosion process,thereby leading to better corrosion resistance of the coatings.The corrosion rates of the HEA coatings with 2200 W and Ti6Al4V substrate are 5.34×10^(-3)mm/a and 2.69×10^(-2)mm/a,respectively.展开更多
In order to enable efficient and cost-effective rehabilitation of surface-worn hydraulic supports,the synthesis and characterization of a novel Ti(N,B)/AISI431 composite coating formed on the surface of 27MnSi steel a...In order to enable efficient and cost-effective rehabilitation of surface-worn hydraulic supports,the synthesis and characterization of a novel Ti(N,B)/AISI431 composite coating formed on the surface of 27MnSi steel are explored via an exothermic in-situ reaction using the ultra-high speed laser cladding(EHLA in German)technique in combination with direct reaction synthesis(DRS).The aim is to mitigate the high residual stress and interfacial stress gradient in the remanufactured AISI431 coating on 27SiMn steel substrate and enhance surface wear resistance.The microstructure,phase composition and interface characteristics are carefully investigated.Much improved wear performance of the composite coating is revealed,mainly attributed to the in-situ formed Ti(N,B)precipitates,refined microstructure,broadened interface zone and reduced residual stress,benefited from the exothermic in-situ Ti(N,B)-reaction.The potential of combining ultra-high speed laser cladding with DRS is demonstrated to create coatings with tailored properties,providing valuable insights for developing advanced wear-resistant materials for industrial applications using EHLA.展开更多
We propose a novel optical intensity modulator based on the combination of a symmetrical metal cladding optical waveguide （SMCW） and ferrofluid, where the ferrofluid is sealed in the waveguide to act as a guiding la...We propose a novel optical intensity modulator based on the combination of a symmetrical metal cladding optical waveguide （SMCW） and ferrofluid, where the ferrofluid is sealed in the waveguide to act as a guiding layer. The light matter interaction in the ferrofluid film leads to the formation of a regular nanoparticle pattern, which changes the phase match condition of the ultrahigh order modes in return. When two lasers are incident on the same spot of the waveguide chip, experiments illustrate all-optical modulation of one laser beam by adjusting the intensity of the other laser. A possible theoretical explanation may be due to the optical trapping and Soret effect since the phenomenon is considerable only when the control laser is effectively coupled into the waveguide.展开更多
The optical fiber with pure quartz core and Fluorine-doped glass cladding was made by POD (plasma outside deposition) technique in some corporations, while we used the creative technique of “overcladding F-doped tube...The optical fiber with pure quartz core and Fluorine-doped glass cladding was made by POD (plasma outside deposition) technique in some corporations, while we used the creative technique of “overcladding F-doped tube onto quartz rod in high temperature” to make the optical fiber which has the same structure as that from POD, in order to research and compare the influence factors on the loss of the fiber, our research work includes contrast experiments on coating polymers with different refractive index and the concentricity error of the fiber core and cladding. The measurement results show us that there are great differences in the loss spectra between the different fiber samples. We made analysis of it.展开更多
The effects of the inter-annealing process on the microstructure,plane stress fracture toughness,and tensile properties of an AA7075 cladding sheet were investigated using optical microscopy,scanning electron microsco...The effects of the inter-annealing process on the microstructure,plane stress fracture toughness,and tensile properties of an AA7075 cladding sheet were investigated using optical microscopy,scanning electron microscopy,electron backscattered diffraction,transmission electron microscopy,and mechanical property tests.The results indicate that the plane stress fracture toughness of AA7075-T6 cladding sheet can be greatly improved.The plane stress fracture toughness for the longitudinal-transverse(L-T)and transverse-longitudinal(T-L)directions were 117.7 and 94.8 MPa·m^(1/2),respectively,after intermediate annealing at 380°C.This represents an increase of 23.9 MPa·m^(1/2)in the L-T direction and 22.6 MPa·m^(1/2) in the T-L direction compared with the AA7075-T6 cladding sheet without intermediate annealing.Moreover,the tensile strength remains similar under different conditions.Microstructure analysis indicates that intermediate annealing before heat treatment can result in long sub-grains,few recrystallized grain boundaries,and small size precipitates in AA7075-T6 cladding sheets.展开更多
To solve the problems of deformation,micro-cracks,and residual tensile stress in laser cladding coatings,the technique of laser cladding with Fe-based memory alloy can be considered.However,the process of in-situ synt...To solve the problems of deformation,micro-cracks,and residual tensile stress in laser cladding coatings,the technique of laser cladding with Fe-based memory alloy can be considered.However,the process of in-situ synthesis of Fe-based memory alloy coatings is extremely complex.At present,there is no clear guidance scheme for its preparation process,which limits its promotion and application to some extent.Therefore,in this study,response surface methodology(RSM)was used to model the response surface between the target values and the cladding process parameters.The NSGA-2 algorithm was employed to optimize the process parameters.The results indicate that the composite optimization method consisting of RSM and the NSGA-2 algorithm can establish a more accurate model,with an error of less than 4.5%between the predicted and actual values.Based on this established model,the optimal scheme for process parameters corresponding to different target results can be rapidly obtained.The prepared coating exhibits a uniform structure,with no defects such as pores,cracks,and deformation.The surface roughness and microhardness of the coating are enhanced,the shaping quality of the coating is effectively improved,and the electrochemical corrosion performance of the coating in 3.5%NaCl solution is obviously better than that of the substrate,providing an important guide for engineering applications.展开更多
This work employed Fe-Cr-C alloy as the cladding material to fabricate wear-resistant coatings on dissimilar steel welded joints composed of NM450 wear-resistant steel and ZG30 SiMn cast steel with ER70-G welding wire...This work employed Fe-Cr-C alloy as the cladding material to fabricate wear-resistant coatings on dissimilar steel welded joints composed of NM450 wear-resistant steel and ZG30 SiMn cast steel with ER70-G welding wire.The investigation focused on elucidating the effect of dilution ratio levels on microstructural distribution and wear behavior within this heterogeneous multi-material system.Owing to its inherently higher chromium(Cr)content,the NM450 region demonstrated more pronounced carbide formation compared to the ER70-G and ZG30 SiMn regions.Microstructural analysis revealed that Cr_(7)C_(3) carbides predominantly formed along grain boundaries,whereas Cr_(23)C_(6) carbides mainly precipitated within grains.After cladding,the wear resistance of the NM450/ER70-G/ZG30 SiMn welded joint was markedly improved,with the high-dilution coating exhibiting superior performance.This enhancement was attributed to favorable thermal conditions in the highdilution scenario,promoting a more homogeneous precipitation of Cr_(23)C_(6).Although significant elemental mixing occurred at the interfacial zones,the top region of the cladding layer remained minimally affected by dilution-induced drawbacks.Accordingly,the high-dilution sample demonstrated better wear resistance than its low-dilution counterpart due to optimized carbide precipitation characteristics.These findings provide basic insights for designing effective cladding strategies for complex multi-material components in demanding industrial applications.展开更多
An all-fiber optical modulator, which is composed of a piece of no-core fiber spliced between two sections of singlemode fibers and uses magnetic fluid（MF） as the cladding of the no-core fiber section, is proposed a...An all-fiber optical modulator, which is composed of a piece of no-core fiber spliced between two sections of singlemode fibers and uses magnetic fluid（MF） as the cladding of the no-core fiber section, is proposed and investigated experimentally. Due to the tunable refractive index and absorption coefficient of MF, the output intensity can be modulated by controlling an applied magnetic field. The dependences of the modulator＇s temporal response on the working wavelength,the magnetic field strength（H）, and the MF＇s concentration are investigated experimentally. The results are explained qualitatively by the dynamic response process of MF under the action of a magnetic field. The findings are helpful for optimizing this kind of modulator.展开更多
The Martian core mainly contains iron,nickel and some light elements.However,controversies remain about the structure and chemical composition of the Martian core due to a lack of samples and marsquake data.Recently,t...The Martian core mainly contains iron,nickel and some light elements.However,controversies remain about the structure and chemical composition of the Martian core due to a lack of samples and marsquake data.Recently,the InSight lander collected long-term marsquake data,which improved the Martian interior structure model.B ased on the preliminary analysis of marsquake data,Mars has a molten liquid core with a radius of around 1700 km.As the Martian core has a smaller density and lower temperature than pure iron at corresponding pressure and temperature conditions,some light elements are introduced to reduce the density and liquidus temperature.With various methods for seismic analysis,in-situ high-pressure and high-temperature experiments,and first-principal calculations,the Martian core composition and evolution models have been updated in the past few years.Here,we review those studies on the light elements in the Martian core from four aspects including(1)high-temperature and high-pressure experiments,(2)marsquake data,(3)mineral physics model with molecular dynamics simulations and(4)cosmochemistry investigation.We discussed the effect of different light elements on the Martian core s density,sound velocity and liquidus temperature.Moreover,the review examines the varieties,abundances and forms of light elements in the Martian core.展开更多
[Objectives]To investigate the clinical efficacy of core stability training combined with conventional rehabilitation in the functional recovery of patients suffering from chronic low back pain.[Methods]A randomized c...[Objectives]To investigate the clinical efficacy of core stability training combined with conventional rehabilitation in the functional recovery of patients suffering from chronic low back pain.[Methods]A randomized controlled trial design was employed in this study.Ninety patients with chronic low back pain were recruited and randomly assigned to either a control group(n=45),which received conventional rehabilitation,or an experimental group(n=45),which received conventional rehabilitation combined with core stability training.Both groups underwent treatment for 6 weeks.Assessments were conducted using the visual analogue scale(VAS),Oswestry disability index(ODI),and finger-to-floor test prior to treatment,6 weeks following treatment,and during the follow-up period,respectively.[Results]Prior to treatment,no statistically significant differences were observed between the two patient groups in terms of general information and various baseline measurements(P>0.05).Following 6 weeks of treatment and throughout the follow-up period,both groups demonstrated significant improvements in VAS scores,ODI scores,and lumbar anteflexion range of motion compared to baseline measurements(P<0.05).Notably,the magnitude of improvement in the experimental group exceeded that of the control group,with this inter-group difference reaching statistical significance(P<0.05).No serious adverse reactions were reported during the treatment process.[Conclusions]Core stability training combined with conventional rehabilitation can significantly enhance the alleviation of pain and functional impairments in patients suffering from chronic low back pain.This approach holds valuable implications for the optimization of rehabilitation treatment protocols.展开更多
基金financially supported by the National High Technology Research and Development Program of China (No. 2013AA030706 and No. 2009AA03Z532)the Fundamental Research Funds for the Central Universities of China (No. FRF-TP-12-146A)
文摘The steady-state temperature field of horizontal core-filling continuous casting （HCFC） for producing copper cladding aluminum rods was simulated by finite element method to investigate the effects of key processing parameters on the positions of solid-liquid interfaces （SLIs） of copper and aluminum. It is found that mandrel tube length and mean withdrawing speed have significant effects on the SLI positions of both copper and aluminum. Aluminum casting temperature （TAI） （1003-1123 K） and secondary cooling water flux （600-900 L.h-1） have little effect on the SLI of copper but cause the SLI of aluminum to move 2-4 mm. When TA1 is in a range of 1043-1123 K, the liquid aluminum can fill continuously into the pre-solidified copper tube. Based on the numerical simulation, reasonable processing parameters were determined.
基金National Natural Science Foundation of China(52071126)Natural Science Foundation of Tianjin City,China(22JCQNJC01240)+2 种基金Central Guidance on Local Science and Technology Development Fund of Hebei Province(226Z1009G)Special Funds for Science and Technology Innovation in Hebei(2022X19)Anhui Provincial Natural Science Foundation(2308085ME135)。
文摘Co-based alloy coating was prepared on Zr alloy using laser melting and cladding technique to study the difference in the high-temperature oxidation behavior between pure metal Co coatings and Co-T800 alloy coatings,as well as the wear resistance of the coatings.Besides,the effect of changing the laser melting process on the coatings was also investigated.The oxidation mass gain at 800–1200℃and the high-temperature oxidation behavior during high-temperature treatment for 1 h of two coated Zr alloy samples were studied.Results show that the Co coating and the Co-T800 coating have better resistance against high-temperature oxidation.After oxidizing at 1000℃for 1 h,the thickness of the oxide layer of the uncoated sample was 241.0μm,whereas that of the sample with Co-based coating is only 11.8–35.5μm.The friction wear test shows that the depth of the abrasion mark of the coated sample is only 1/2 of that of the substrate,indicating that the hardness and wear resistance of the Zr substrate are greatly improved.The disadvantage of Co-based coatings is the inferior corrosion resistance in 3.5wt%NaCl solution.
基金Supported by Zhejiang Provincial Natural Science Foundation of China under Grant Nos Y5090150 and Y6100244the National Natural Science Foundation of China under Grant No 61007051.
文摘A refractive index(RI)sensor based on a cladding-etched thin-core single-mode fiber(TCSMF)sandwiched between two single-mode fibers is demonstrated.The experimental results show that the sensitivity,within the RI range of 1.333–1.340,is enhanced at least 6 times by etching.It increases with the surrounding RI and reaches 857.5 nm/RIU at RI of 1.3684,and it can be expected to be higher with the decrease of the cladding diameter of the TCSMF.
基金National Natural Science Foundation of China(51764038)Gansu Science and Technology Planning Project(2022JR5RA314,22YF7WA151,22YF7GA138,23CXGA0151)+1 种基金Gansu Provincial Department of Education:Industrial Support Plan Project(2022CYZC-31)Gansu Provincial Association of Science and Technology Innovation Driving Force Project(GXH20230817-10)。
文摘The high-entropy alloy composite coatings AlCu_(2)Ti(NiCr)_(2)-(WC)_(x)(x denotes powder feeding speeds,including 0,25,50,and 75 r/min)were prepared by plasma cladding using a hybrid mode of AlCu_(2)(NiCr)_(2)Ti cable-type welding wire(CWW)and tungsten carbide(WC)powder.The effect of WC powder feeding speed on the microstructure,hardness,and wear properties of the prepared coatings was investigated.The results show that the coatings consist of body-centered cubic main phases and face-centered cubic secondary phases,with carbide reinforcement phases formed due to the addition of WC.The hardness and wear resistance of the coatings are significantly improved compared to the TC11 substrate.When WC powder feeding speed is set at 50 r/min,the coating exhibits optimal wear resistance,with a minimum volume wear rate of 8.5869×10^(-6)mm^(3)·N^(-1)·m^(-1),greatly improving the wear properties of TC11 surface.The coincident CWW-powder plasma cladding provides a viable method for the preparation of highentropy alloy composite coatings with enhanced wear resistance.
文摘Aseries of [(Fe_(0.6)Co_(0.2)Ni_(0.2))_(0.75-0.03x)B_(0.2)Si_(0.05+0.03x)]_(96)Nb_(4) amorphous alloy composite coatings were prepared by adjusting the silicon content(x=0,1,2,3,4,5,and 6)and their microstructures and tribological properties were investigated by laser cladding technique.Additionally,the effect of Si on the glass forming ability(GFA)of the layers was understood.Results show that an appropriate Si content can refine the microstructure of the FeCoNiBSiNb laser cladding layers and improve the mechanical and tribological properties.The hardness of the coating layer increases monotonically with the Si content.At the Si content of 4.8at%(x=0),the coating layer exhibits a relatively low hardness(734.2HV 0.1).Conversely,at the silicon content of 13.44at%(x=3),the coating layer exhibits the highest hardness(1106HV 0.1).The non-crystalline content and tensile strength exhibit an initial increase,followed by a subsequent decrease.At x=2,the coating exhibits its maximum fracture strength(2880 MPa).However,when x>2,the fracture strength of the coating decreases with an increase in x.Conversely,with an increase in Si content,the wear volume loss initially decreases and then increases.At a Si content of 10.56at%(x=2),the coating exhibits the highest non-crystalline content(42%),the highest tensile strength(2880 MPa),and the most favorable dry friction performance.
文摘The failure of mechanical components is mainly caused by three key mechanisms:wear,corrosion,and fatigue.Among these failure modes,wear of mechanical components notably increases energy consumption and leads to substantial economic losses.Fe-Cr-C-B-Ti-Y wear-resistant cladding metals were prepared by the plasma cladding method.The wear performance of the cladding metals was analyzed using an MLS-23 rubber wheel wet sand wear tester.X-ray diffraction,scanning electron microscope,electron backscatter diffraction,and transmission electron microscope were employed to investigate the phase composition and microstructure of the cladding metals,followed by a discussion of their strengthening and wear mechanisms.The results indicate that the microstructure of Fe-Cr-C-B-Ti-Y cladding metals is composed of austeniteγ-Fe,M_(23)(C,B)_(6)eutectic carbide,and TiC hard phase.As the Y_(2)O_(3)content increases,the hardness and wear resistance of the cladding metal show a trend of first increasing and then decreasing.When the Y_(2)O_(3)content is 0.4wt%,the precipitation of TiC hard phase and M_(23)(C,B)_(6)-type eutectic carbides reaches maximum,and the grain size is the finest.The cladding metal exhibits optimal formability,featuring the smallest wetting angle of 52.2°.Under this condition,the Rockwell hardness value of the cladding metal is 89.7 HRC,and the wear mass loss is 0.27 g.The dominant wear mechanism of cladding metals is abrasive wear,and the material removal process involves micro-cutting and plowing.
基金supported by the National Natural Science Foundation of China(52161007)Science and Technology Planning Project of Guangdong Province of China(20170902,20180902)+1 种基金Science and Technology Planning Project of Yangjiang City of Guangdong Province(SDZX2020009)Research project of Shenzhen city(JSGG20210420091802007).
文摘In order to enhance the wear resistance of 45 steel,a WC/Stellite 6 composite layer with 30%WC which with different morphologies(spherical and irregular)was prepared on the surface of 45 steel by laser cladding technology.The effects of WC morphology on the phase composition,microstructure,microhardness,and wear resistance of the cladding layer were compared and analyzed.The res-ults show that the surface of the cladding layer was well formed.M_(23)C_(6),M_(7)C_(3),WC,and W_(2)C exist in both cladding layers.With the ad-dition of spherical WC,the diffraction peaks of γ-Co appear on the left side of the main peak of Co6W6C.The area of intergranular carbides accounts for a large proportion in the surface layer which with the fine grains.During the process of laser cladding the spherical WC particles with loose structure are prone to melting,including their interior.However,the melting amount of irregular WC particles is finite,which only occurs on the periphery of the particles,and the particle interior is relatively intact.The microhard-ness of two cladding layers gradient increases from the substrate to the surface layer.The surface layer added spherical WC has high-er microhardness,which reaches 790.6 HV1.Nevertheless,the wear resistance of the cladding layer added irregular WC is better than that of the cladding layer added spherical WC.The reason is because that the incompletely melted irregular WC particles are uni-formly distributed in the cladding layer which provided the support points for the cladding layer matrix during the wear process,the wear of the cladding layer by the grinding pair is reduced consequently.
基金supported by the Jiangxi Provincial Natural Science Foundation of China(Grant number 20224BAB204049)the National Natural Science Foundation of China(Grant number 52205194)the Fund Project of Jiangxi Provincial Department of Education(Grant number GJJ2200602)。
文摘Conventional Fe-C alloy parts used in mechanical transmission and braking systems exposed to the external environment often suffer from wear and corrosion failures.Surface coating strengthening technologies have been explored to improve the surface performance and prolong service life of these parts.Among these technologies,laser cladding has shown promise in producing Fe-based alloy coatings with superior interfacial bonding properties to the Fe-C alloy substrate.Additionally,the microstructure of the Fe-based alloy coating is more uniform and the grain size is finer than that of surfacing welding,thermal spraying,and plasma cladding,and the oxide film of alloying elements on the coating surface can improve the coating performance.However,Fe-based alloy coatings produced by laser cladding typically exhibit lower hardness,lower wear resistance,corrosion resistance,and oxidation resistance compared to coatings based on Co and Ni alloys.Moreover,these coatings are susceptible to defects such as pores and cracks.To address these limitations,the incorporation of rare-earth oxides through doping in the laser cladding process has garnered significant attention.This approach has demonstrated substantial improvements in the microstructure and properties of Fe-based alloy coatings.This paper reviewed recent research on the structure and properties of laser-cladded Fe-based alloy coatings doped with various rare earth oxides,including La_(2)O_(3),CeO_(2),and Y_(2)O_(3).Specifically,it discussed the effects of rare earth oxides and their concentrations on the structure,hardness,friction,wear,corrosion,and oxidation characteristics of these coatings.Furthermore,the mechanisms by which rare earth oxides influence the coating’s structure and properties were summarized.This review aimed to serve as a valuable reference for the application and advancement of laser cladding technology for rare earth modified Fe-based alloy coatings.
文摘Cladding light strippers(CLSs)are essential components for high-power monolithic fiber laser systems.Because they allow for bending of the fiber,which leads to an excellent stripping efficiency of light with a low ray angle,refractive index-based CLSs have an advantage over the commonly used alternative approaches.However,conventional high-index CLSs overheat at relatively low input power as the maximum temperature,located in a hot-spot,increases linearly with the input power.This applies particularly to CLSs in thulium-based fiber systems,where very low power can already lead to extreme heat generation due to the high cladding material absorption around 2μm.Here,we investigate materials with a highly negative thermooptical coefficient combined with a refractive index closely above glass to distribute the stripped power and heat uniformly along an increased fiber length.Analyzing multiple CLS geometries for fiber diameters of 125 and 400μm,we show record-high maximum input powers for single-material CLSs of 21.8 W for the signal(2039 nm)and 675 W for the pump wavelength(793 nm).Transmitting excess light instead of overheating,this wavelength-adaptable self-protecting CLS concept is fast to apply onsite in the lab and reaches stripping efficiencies of>40 dB in the bent version.
基金the National Natural Science Foundation of China(Nos.52001037,U2037601,U21A2048)the National Key Research and Development Program of China(No.2022YFB3709300).
文摘In order to improve the surface properties of titanium alloys,a novel TiFeNiCuV high-entropy alloy(HEA)coating was prepared on a Ti−6Al−4V(TC4)substrate via laser cladding under different laser powers.The microstructure,microhardness,and friction wear properties of the coatings were systematically investigated.The results showed that at laser powers of 1200 and 2000 W,the microstructure of the coatings exhibited a core-shell dendritic structure.At 2800 W,the coatings displayed a daisy-like eutectic structure.The average hardness of the coatings reached HV 692.281 owing to solid-solution and fine-grain strengthening.Wear mechanisms of the coatings at room temperature primarily involved fatigue and slight oxidation wear.The total volume loss of the coatings was 4.22×10^(−3)mm^(3),which was 14.47%that of the TC4,indicating excellent wear resistance.
基金Projects(2022YFC2406000,52201067)supported by the National Natural Science Foundation of ChinaProject(2019BT02C629)supported by the Guangdong Special Support Program,China+8 种基金Project(2022GDASZH-2022010107)supported by the Guangdong Academy of Science Projects,ChinaProject(2022GDASZH-2022010203-003)supported by GDAS Projects of International Cooperation Platform of Science and Technology,ChinaProject(2022B1515250004)supported by the Guangdong Basic and Applied Basic Research Foundation,ChinaProjects(2023B1212120008,2023B1212060045)supported by the Guangdong Province Science and Technology Plan Projects,ChinaProject(2024KTSCX191)supported by the Guangdong Province General University Characteristic Innovation Project,ChinaProject(SKXRC202403)supported by the Guangdong Association for Science and Technology,ChinaProjects(QT-2023-038,QT2024-016)supported by the Young Talent Support Project of Guangzhou Association for Science and Technology,ChinaProject(023AFB057)supported by the Natural Science Foundation of Hubei Province,ChinaProject(2023780200040009603)supported by the Jiangmen Science and Technology Plan Projects,China。
文摘This work investigated tribological behavior and corrosion resistance of laser cladding(LC)Ti_(50)Nb_(15)V_(15)Zr_(5)Cr_(5)Al_(10)high-entropy alloy(HEA)coatings on Ti6Al4V substrates.Microstructural characterization illustrated that there was only body centered cubic phase in the HEA coating.Besides,the coatings of different laser power all exhibited obviously higher hardness than the substrate.It is illustrated that the microstructure of the HEA coatings is composed of body centered cubic phase,and the temperature gradient contributes to the distribution difference between the equiaxed and columnar grains.Meanwhile,the relationships between the tribological behavior,corrosion resistance and alloying elements have been illustrated.The HEA coating with 2200 W holds the best wear and corrosion resistance.During the friction process,there are many oxides formed at high temperatures,and adhesive wear contributes most to the wear mechanism of the coatings.The wear volumes of the HEA coatings are only 24.7%to 45.5%of that of the Ti6Al4V substrate.Due to the alloying elements like Cr and Al,there is dense passive film formed during the corrosion process,thereby leading to better corrosion resistance of the coatings.The corrosion rates of the HEA coatings with 2200 W and Ti6Al4V substrate are 5.34×10^(-3)mm/a and 2.69×10^(-2)mm/a,respectively.
基金financially supported by the National Key Research and Development Program of China(No.2023YFB4606200)Technical Development Foundation of China Academy of Machinery Science and Technology Group(No.812201Q9)+2 种基金Fundamental Research Funds of National Institute of Metrology of China(No.AKYRC2401)Beijing Natural Science Foundation(No.2222093)the National Key Research and Development Program of China(No.2021YFB3702003)。
文摘In order to enable efficient and cost-effective rehabilitation of surface-worn hydraulic supports,the synthesis and characterization of a novel Ti(N,B)/AISI431 composite coating formed on the surface of 27MnSi steel are explored via an exothermic in-situ reaction using the ultra-high speed laser cladding(EHLA in German)technique in combination with direct reaction synthesis(DRS).The aim is to mitigate the high residual stress and interfacial stress gradient in the remanufactured AISI431 coating on 27SiMn steel substrate and enhance surface wear resistance.The microstructure,phase composition and interface characteristics are carefully investigated.Much improved wear performance of the composite coating is revealed,mainly attributed to the in-situ formed Ti(N,B)precipitates,refined microstructure,broadened interface zone and reduced residual stress,benefited from the exothermic in-situ Ti(N,B)-reaction.The potential of combining ultra-high speed laser cladding with DRS is demonstrated to create coatings with tailored properties,providing valuable insights for developing advanced wear-resistant materials for industrial applications using EHLA.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11274091 and 11274092)the Fundamental Research Funds for the Central Universities of Hohai University, China (Grant No. 2011B11014)
文摘We propose a novel optical intensity modulator based on the combination of a symmetrical metal cladding optical waveguide （SMCW） and ferrofluid, where the ferrofluid is sealed in the waveguide to act as a guiding layer. The light matter interaction in the ferrofluid film leads to the formation of a regular nanoparticle pattern, which changes the phase match condition of the ultrahigh order modes in return. When two lasers are incident on the same spot of the waveguide chip, experiments illustrate all-optical modulation of one laser beam by adjusting the intensity of the other laser. A possible theoretical explanation may be due to the optical trapping and Soret effect since the phenomenon is considerable only when the control laser is effectively coupled into the waveguide.
文摘The optical fiber with pure quartz core and Fluorine-doped glass cladding was made by POD (plasma outside deposition) technique in some corporations, while we used the creative technique of “overcladding F-doped tube onto quartz rod in high temperature” to make the optical fiber which has the same structure as that from POD, in order to research and compare the influence factors on the loss of the fiber, our research work includes contrast experiments on coating polymers with different refractive index and the concentricity error of the fiber core and cladding. The measurement results show us that there are great differences in the loss spectra between the different fiber samples. We made analysis of it.
基金the National Key R&D Program of China(Nos.2023YFB3710401,2022YFB3504401)the National Natural Science Foundation of China(Nos.52271094,U1708251)+1 种基金the Key Research and Development Program of Liaoning,China(No.2020JH2/10700003)Qingyuan City Science and Technology Plan Project(No.2023YFJH003),China.
文摘The effects of the inter-annealing process on the microstructure,plane stress fracture toughness,and tensile properties of an AA7075 cladding sheet were investigated using optical microscopy,scanning electron microscopy,electron backscattered diffraction,transmission electron microscopy,and mechanical property tests.The results indicate that the plane stress fracture toughness of AA7075-T6 cladding sheet can be greatly improved.The plane stress fracture toughness for the longitudinal-transverse(L-T)and transverse-longitudinal(T-L)directions were 117.7 and 94.8 MPa·m^(1/2),respectively,after intermediate annealing at 380°C.This represents an increase of 23.9 MPa·m^(1/2)in the L-T direction and 22.6 MPa·m^(1/2) in the T-L direction compared with the AA7075-T6 cladding sheet without intermediate annealing.Moreover,the tensile strength remains similar under different conditions.Microstructure analysis indicates that intermediate annealing before heat treatment can result in long sub-grains,few recrystallized grain boundaries,and small size precipitates in AA7075-T6 cladding sheets.
基金financial supports from the National Natural Science Foundation of China-Youth Project(51801076)the Provincial Colleges and Universities Natural Science Research Project of Jiangsu Province(18KJB430009)+1 种基金the Postdoctoral Research Support Project of Jiangsu Province(1601055C)the Senior Talents Research Startup of Jiangsu University(14JDG126)。
文摘To solve the problems of deformation,micro-cracks,and residual tensile stress in laser cladding coatings,the technique of laser cladding with Fe-based memory alloy can be considered.However,the process of in-situ synthesis of Fe-based memory alloy coatings is extremely complex.At present,there is no clear guidance scheme for its preparation process,which limits its promotion and application to some extent.Therefore,in this study,response surface methodology(RSM)was used to model the response surface between the target values and the cladding process parameters.The NSGA-2 algorithm was employed to optimize the process parameters.The results indicate that the composite optimization method consisting of RSM and the NSGA-2 algorithm can establish a more accurate model,with an error of less than 4.5%between the predicted and actual values.Based on this established model,the optimal scheme for process parameters corresponding to different target results can be rapidly obtained.The prepared coating exhibits a uniform structure,with no defects such as pores,cracks,and deformation.The surface roughness and microhardness of the coating are enhanced,the shaping quality of the coating is effectively improved,and the electrochemical corrosion performance of the coating in 3.5%NaCl solution is obviously better than that of the substrate,providing an important guide for engineering applications.
文摘This work employed Fe-Cr-C alloy as the cladding material to fabricate wear-resistant coatings on dissimilar steel welded joints composed of NM450 wear-resistant steel and ZG30 SiMn cast steel with ER70-G welding wire.The investigation focused on elucidating the effect of dilution ratio levels on microstructural distribution and wear behavior within this heterogeneous multi-material system.Owing to its inherently higher chromium(Cr)content,the NM450 region demonstrated more pronounced carbide formation compared to the ER70-G and ZG30 SiMn regions.Microstructural analysis revealed that Cr_(7)C_(3) carbides predominantly formed along grain boundaries,whereas Cr_(23)C_(6) carbides mainly precipitated within grains.After cladding,the wear resistance of the NM450/ER70-G/ZG30 SiMn welded joint was markedly improved,with the high-dilution coating exhibiting superior performance.This enhancement was attributed to favorable thermal conditions in the highdilution scenario,promoting a more homogeneous precipitation of Cr_(23)C_(6).Although significant elemental mixing occurred at the interfacial zones,the top region of the cladding layer remained minimally affected by dilution-induced drawbacks.Accordingly,the high-dilution sample demonstrated better wear resistance than its low-dilution counterpart due to optimized carbide precipitation characteristics.These findings provide basic insights for designing effective cladding strategies for complex multi-material components in demanding industrial applications.
基金Project supported by the Natural Science Foundation of Tianjin City,China(Grant No.13JCYBJC16100)the National Natural Science Foundation of China(Grant No.61107035)+1 种基金the National Key Scientific Instrument and Equipment Development Project of China(Grant No.2013YQ03091502)the National Basic Research Program of China(Grant Nos.2010CB327802 and 2010CB327806)
文摘An all-fiber optical modulator, which is composed of a piece of no-core fiber spliced between two sections of singlemode fibers and uses magnetic fluid（MF） as the cladding of the no-core fiber section, is proposed and investigated experimentally. Due to the tunable refractive index and absorption coefficient of MF, the output intensity can be modulated by controlling an applied magnetic field. The dependences of the modulator＇s temporal response on the working wavelength,the magnetic field strength（H）, and the MF＇s concentration are investigated experimentally. The results are explained qualitatively by the dynamic response process of MF under the action of a magnetic field. The findings are helpful for optimizing this kind of modulator.
基金financially supported by the National Natural Science Foundation of China(grant no.42120104005)Guizhou Provincial 2021 Science and Technology Subsidies(grant no.GZ2021SIG)+1 种基金Guizhou Provincial Science and Technology Projects(grant nos.ZK[2024]087GCC[2023]060)。
文摘The Martian core mainly contains iron,nickel and some light elements.However,controversies remain about the structure and chemical composition of the Martian core due to a lack of samples and marsquake data.Recently,the InSight lander collected long-term marsquake data,which improved the Martian interior structure model.B ased on the preliminary analysis of marsquake data,Mars has a molten liquid core with a radius of around 1700 km.As the Martian core has a smaller density and lower temperature than pure iron at corresponding pressure and temperature conditions,some light elements are introduced to reduce the density and liquidus temperature.With various methods for seismic analysis,in-situ high-pressure and high-temperature experiments,and first-principal calculations,the Martian core composition and evolution models have been updated in the past few years.Here,we review those studies on the light elements in the Martian core from four aspects including(1)high-temperature and high-pressure experiments,(2)marsquake data,(3)mineral physics model with molecular dynamics simulations and(4)cosmochemistry investigation.We discussed the effect of different light elements on the Martian core s density,sound velocity and liquidus temperature.Moreover,the review examines the varieties,abundances and forms of light elements in the Martian core.
文摘[Objectives]To investigate the clinical efficacy of core stability training combined with conventional rehabilitation in the functional recovery of patients suffering from chronic low back pain.[Methods]A randomized controlled trial design was employed in this study.Ninety patients with chronic low back pain were recruited and randomly assigned to either a control group(n=45),which received conventional rehabilitation,or an experimental group(n=45),which received conventional rehabilitation combined with core stability training.Both groups underwent treatment for 6 weeks.Assessments were conducted using the visual analogue scale(VAS),Oswestry disability index(ODI),and finger-to-floor test prior to treatment,6 weeks following treatment,and during the follow-up period,respectively.[Results]Prior to treatment,no statistically significant differences were observed between the two patient groups in terms of general information and various baseline measurements(P>0.05).Following 6 weeks of treatment and throughout the follow-up period,both groups demonstrated significant improvements in VAS scores,ODI scores,and lumbar anteflexion range of motion compared to baseline measurements(P<0.05).Notably,the magnitude of improvement in the experimental group exceeded that of the control group,with this inter-group difference reaching statistical significance(P<0.05).No serious adverse reactions were reported during the treatment process.[Conclusions]Core stability training combined with conventional rehabilitation can significantly enhance the alleviation of pain and functional impairments in patients suffering from chronic low back pain.This approach holds valuable implications for the optimization of rehabilitation treatment protocols.
