Fe-Ni alloy, as a widely applied ferromagnetic material, is synthesized using selective laser melting （SLM）. The chemical compositions and microstructure of the SLM Fe-Ni alloy are characterized by X-ray diffraction...Fe-Ni alloy, as a widely applied ferromagnetic material, is synthesized using selective laser melting （SLM）. The chemical compositions and microstructure of the SLM Fe-Ni alloy are characterized by X-ray diffraction （XRD）, energy dispersive X-ray spectroscopy and scanning electron microscopy. It was found that the samples exhibited fine grains with homogenous distribution when a low laser scanning velocity was used. Moreover, the magnetic properties of the samples with different laser parameters are also measured. It shows that the SLM Fe-30%Ni alloy possesses a low coercivity and high saturation magnetization. It also can be obtained that SLM is an alternative faster method to prepare soft magnetic material with complex shapes. Moreover, the magnetic properties can be influenced by the laser parameters.展开更多
The selective laser melting （SLM） of Ti-Ni mixed powder with atomic ratio of 1：1 was performed in the present work in order to elaborate shape memory alloy （SMA）. The martensite phase of Ti-Ni alloy can be found ...The selective laser melting （SLM） of Ti-Ni mixed powder with atomic ratio of 1：1 was performed in the present work in order to elaborate shape memory alloy （SMA）. The martensite phase of Ti-Ni alloy can be found by X-ray diffraction （XRD） analysis under temperature field, moreover, the Ti2Ni phase at a high scanning velocity. The crystalline phase images also show that the synthesized Ti-Ni alloy possessed a refined martensite microstructure. In order to evaluate the mechanical properties, the microhardness and porosity were measured. The microhardness is relatively high about 400HVo.2 with champ temperature. Besides, the porosity is quite low due to the excellent laser energy absorptivity and meltability of Ni element. The differential scanning calorimetry （DSC） analysis shows that the transformation temperature from austenite phase to martensite phase is relatively high and stable.展开更多
The deformation behaviour of spray particles impacting upon a substrate under the oblique impact condition in cold spraying was investigated using finite element analysis(FEA)method.The effect of incidence angle of pa...The deformation behaviour of spray particles impacting upon a substrate under the oblique impact condition in cold spraying was investigated using finite element analysis(FEA)method.The effect of incidence angle of particle on the deformation of particle and substrate was examined.It is found that the contact area between the deformed particle and substrate decreases and the crater depth in the substrate reduces with increasing the tilting angle at the same impact velocity.The normal component of impact velocity takes an important role in the impacting process and formation of bonding.展开更多
Polyetheretherketone (PEEK) based composite materials become of great interest to applications as bearing and slider materials due to their excellent tribological performance. In present work, graphite and MoS2 (7%, w...Polyetheretherketone (PEEK) based composite materials become of great interest to applications as bearing and slider materials due to their excellent tribological performance. In present work, graphite and MoS2 (7%, wt) filled PEEK coatings were prepared using serigraph technique. Employing a uniform design experiment, the friction behavior of the composite coatings was systematically investigated under dry sliding conditions on a ball-on-disc arrangement. The evolution mechanism of coating friction coefficient was discussed. Correlation of coatings friction coefficient with sliding velocity and applied load was accomplished using stepwise regression method. The results indicate that friction coefficients of PEEK + MoS2 and PEEK + graphite coating decrease while increasing applied load. Moreover, friction coefficient of PEEK + MoS2 coating increases with increasing sliding velocity.展开更多
The effect of vacuum heat treatment on the microstructure and microhardness of cold-sprayed Cu-4%Cr-2%Nb alloy coating was investigated. The heat treatment was conducted under the temperatures from 250 ℃ to 950 ℃ wi...The effect of vacuum heat treatment on the microstructure and microhardness of cold-sprayed Cu-4%Cr-2%Nb alloy coating was investigated. The heat treatment was conducted under the temperatures from 250 ℃ to 950 ℃ with a step of 100 ℃ for 2 h. It was found that a dense thick Cu-4Cr-2Nb coating could be formed by cold spraying. After heat treatment, a Cr2Nb phase was uniformly distributed in the matrix, which was transferred from the gas-atomized feedstock. A little grain growth of Cr2Nb phase was observed accompanying with the healing-up of the incomplete interfaces between the deposited particles at the elevated temperatures. The coating microhardness increases a little with increasing the temperature to 350 ℃, and then decreases with further increasing temperature up to 950 ℃. This fact can be attributed to the microstructure evolution during the heat treatment.展开更多
Numerical simulations focusing on the impacting behavior of cold sprayed particles were usually conducted by the Lagrangian formulation.However,the calculated outputs were much dependent on the meshing size owing to t...Numerical simulations focusing on the impacting behavior of cold sprayed particles were usually conducted by the Lagrangian formulation.However,the calculated outputs were much dependent on the meshing size owing to the excessive element distortion.Therefore,the Eulerian formulation becomes attractive,because it can avoid the extreme distortion of elements.In the present study,a copper particle impact on the same material substrate in cold spraying was simulated using the Eulerian formulation available in the ABAQUS software(Ver 6.8).The dependency of the calculated outputs on the meshing resolution were detailedly investigated.Results show that the meshing resolution not only has an effect on the shape of the deformed particle,but also it can significantly influence the maximum plastic strain and temperature under a given impact velocity.In addition,the copper particle deformation process at the critical velocity of 310 m/s shows that a jet composed of both of the particle and substrate materials can be formed and gets elongated with the impact time.展开更多
Effect of high static magnetic field on the dendritic morphology and growth direction in directionally solidified Al-10 wt.%Zn alloy were studied by three-dimensional(3D) X-ray micro-computed tomography, Electron Back...Effect of high static magnetic field on the dendritic morphology and growth direction in directionally solidified Al-10 wt.%Zn alloy were studied by three-dimensional(3D) X-ray micro-computed tomography, Electron Back-scattered Diffraction(EBSD) and X-ray Diffraction(XRD). The application of high static axial magnetic field(5T) during directional solidification was found to destabilize the solid/liquid interface and cause the growth direction of dendrite deviate from thermal gradient, leading to irregular solid/liquid interfacial shape and cellular to dendritic morphology transition. The thermoelectric magnetic convection(TEMC) caused by the interaction of thermoelectric effect and magnetic field was supposed to be responsible for the transition. In addition, the EBSD and XRD results confirm that the preferred growth direction of α-Al was found to transform from the traditionally expected <100> to<110>. The dendrite orientation transition(DOT) in Al-10 wt.%Zn alloy can be attributed to the effect of applied magnetic field on the anisotropy of crystal during solidification. The result indicates the potential application of high static magnetic field in altering the morphology and preferred growth direction of dendrite during directional solidification.展开更多
Cold-sprayed magnesium coatings have been little researched although cold spraying has been applied to deposit a large number of materials such as metals,metal matrix composites.In the present study,helium gas and air...Cold-sprayed magnesium coatings have been little researched although cold spraying has been applied to deposit a large number of materials such as metals,metal matrix composites.In the present study,helium gas and air were employed as the propelling gases to deposit Mg coatings under the temperature of 600℃and 630℃.The effect of gas types on the coating microstructure was investigated.It is much interesting to find that the particle deposition efficiency using helium gas as propelling gas is lower than that using air.This suggests that strong erosion occurred during cold spraying using helium gas.The porosity of the coating using helium gas is lower than that using air.In addition,the in-flight particle velocity was also simulated by the FLUENT software to explore the effect of gas types.The modeled results show that the in-flight particle velocity using helium is higher than the erosion velocity of Mg particle.展开更多
Manufacturing of solid oxide fuel cell （SOFC） components remains nowadays a key point for the indus- trial development of this technology. Especially, the deposition of the dense electrolyte layer which is sand- wic...Manufacturing of solid oxide fuel cell （SOFC） components remains nowadays a key point for the indus- trial development of this technology. Especially, the deposition of the dense electrolyte layer which is sand- wiched between the porous anode and the porous cathode is of paramount importance and thus focuses a lot of attention. Therefore, this paper considers and reviews recent developments concerning solid electrolyte layers manufacturing using thermal spray （TS） and physical vapour deposition （PVD） technologies.展开更多
A columnar Al film was firstly deposited on the top of 7%Y2O3？stabilized zirconia （7YSZ） ceramic coating in thermal barrier coating （TBC） system by magnetron sputtering. A vacuum treatment was then carried out at...A columnar Al film was firstly deposited on the top of 7%Y2O3？stabilized zirconia （7YSZ） ceramic coating in thermal barrier coating （TBC） system by magnetron sputtering. A vacuum treatment was then carried out at 700 °C for 1 h and 900 °C for 5 h to improve the erosion resistance of Al-deposited TBC. Aα-Al2O3 layer was in situ synthesized on the top of 7YSZ coating via vacuum heat treatment. The microstructure evolution of Al-deposited TBC illustrated that a loose surface-layer and a dense sub-layer formed on the top of 7YSZ coating after vacuum treatment. The phase structures of the as-sprayed TBC and the Al-deposited TBC after vacuum heat treatment were characterized by X-ray diffraction （XRD） and transmission electron microscope （TEM） assisted with focused ion beam （FIB）. Particulate erosion resistances of the as-sprayed TBC and treated TBC were compared at room temperature. In addition, erosion mechanism and schematic diagram were proposed. The results show that the Al-deposited TBC after vacuum heat treatment has better particulate erosion resistance than the as-sprayed one.展开更多
In order to realize a general-purpose automatic formal verification platform based on WebAssembly technology as a web service(FVPS),which aims to provide an automated report of vulnerability detections,this work build...In order to realize a general-purpose automatic formal verification platform based on WebAssembly technology as a web service(FVPS),which aims to provide an automated report of vulnerability detections,this work builds a Hyperledger Fabric blockchain runtime model.It proposes an optimized methodology of the functional equivalent translation from source program languages to formal languages.This methodology utilizes an external application programming interface(API)table to replace the source codes in compilation,thereby pruning the part of housekeeping codes to ease code inflation.Code inflation is a significant metric in formal language translation.Namely,minor code inflation enhances verification scale and performance efficiency.It determines the efficiency of formal verification,involving launching,running,and memory usage.For instance,path explosion increases exponentially,resulting in out-of-memory.The experimental results conclude that program languages like golang severely impact code inflation.FVPS reduces the wasm code size by over 90%,achieving two orders of optimization magnitude,from 2000 kilobyte(KB)to 90 KB.That means we can cope with golang applications up to 20 times larger than the original in scale.This work eliminates the gap between Hyperledger Fabric smart contracts and WebAssembly.Our approach is pragmatic,adaptable,extendable,and flexible.Nowadays,FVPS is successfully applied in a Railway-Port-Aviation blockchain transportation system.展开更多
Yttria-stabilized zirconia（ YSZ） coatings were deposited by low pressure plasma spray（ LPPS） in 1.0× 10^4 Pa,1.5 × 10^4 Pa,and 2.5 × 10^4 Pa. Both in-flight particle diagnostic detected by DPV-2000 ...Yttria-stabilized zirconia（ YSZ） coatings were deposited by low pressure plasma spray（ LPPS） in 1.0× 10^4 Pa,1.5 × 10^4 Pa,and 2.5 × 10^4 Pa. Both in-flight particle diagnostic detected by DPV-2000 system and ANSYS-FLUENT software were used to study the connection between the parameters of flying particles and the coating formation,which might help to recognize the relationship between the operation parameters and the coatings quality. The results of simulation showed that particles in a lower spray pressure could achieve a higher velocity. The particle velocity was around 380 m/s at a distance of 35 cm from the nozzle at 1.0 × 10^4 Pa while only 300 m/s at 2.5 × 10^4 Pa in actual measurement.The results showed that the velocity of particles increased with decreasing the spray pressure,which might enhance the flattening rate of coatings and thereby decreased the porosity. The deposited YSZ coating with the lowest porosity can be gained under 1.0 × 10^4 Pa condition.展开更多
文摘Fe-Ni alloy, as a widely applied ferromagnetic material, is synthesized using selective laser melting （SLM）. The chemical compositions and microstructure of the SLM Fe-Ni alloy are characterized by X-ray diffraction （XRD）, energy dispersive X-ray spectroscopy and scanning electron microscopy. It was found that the samples exhibited fine grains with homogenous distribution when a low laser scanning velocity was used. Moreover, the magnetic properties of the samples with different laser parameters are also measured. It shows that the SLM Fe-30%Ni alloy possesses a low coercivity and high saturation magnetization. It also can be obtained that SLM is an alternative faster method to prepare soft magnetic material with complex shapes. Moreover, the magnetic properties can be influenced by the laser parameters.
文摘The selective laser melting （SLM） of Ti-Ni mixed powder with atomic ratio of 1：1 was performed in the present work in order to elaborate shape memory alloy （SMA）. The martensite phase of Ti-Ni alloy can be found by X-ray diffraction （XRD） analysis under temperature field, moreover, the Ti2Ni phase at a high scanning velocity. The crystalline phase images also show that the synthesized Ti-Ni alloy possessed a refined martensite microstructure. In order to evaluate the mechanical properties, the microhardness and porosity were measured. The microhardness is relatively high about 400HVo.2 with champ temperature. Besides, the porosity is quite low due to the excellent laser energy absorptivity and meltability of Ni element. The differential scanning calorimetry （DSC） analysis shows that the transformation temperature from austenite phase to martensite phase is relatively high and stable.
基金Project(50476075)supported by the National Natural Science Foundation of China
文摘The deformation behaviour of spray particles impacting upon a substrate under the oblique impact condition in cold spraying was investigated using finite element analysis(FEA)method.The effect of incidence angle of particle on the deformation of particle and substrate was examined.It is found that the contact area between the deformed particle and substrate decreases and the crater depth in the substrate reduces with increasing the tilting angle at the same impact velocity.The normal component of impact velocity takes an important role in the impacting process and formation of bonding.
文摘Polyetheretherketone (PEEK) based composite materials become of great interest to applications as bearing and slider materials due to their excellent tribological performance. In present work, graphite and MoS2 (7%, wt) filled PEEK coatings were prepared using serigraph technique. Employing a uniform design experiment, the friction behavior of the composite coatings was systematically investigated under dry sliding conditions on a ball-on-disc arrangement. The evolution mechanism of coating friction coefficient was discussed. Correlation of coatings friction coefficient with sliding velocity and applied load was accomplished using stepwise regression method. The results indicate that friction coefficients of PEEK + MoS2 and PEEK + graphite coating decrease while increasing applied load. Moreover, friction coefficient of PEEK + MoS2 coating increases with increasing sliding velocity.
文摘The effect of vacuum heat treatment on the microstructure and microhardness of cold-sprayed Cu-4%Cr-2%Nb alloy coating was investigated. The heat treatment was conducted under the temperatures from 250 ℃ to 950 ℃ with a step of 100 ℃ for 2 h. It was found that a dense thick Cu-4Cr-2Nb coating could be formed by cold spraying. After heat treatment, a Cr2Nb phase was uniformly distributed in the matrix, which was transferred from the gas-atomized feedstock. A little grain growth of Cr2Nb phase was observed accompanying with the healing-up of the incomplete interfaces between the deposited particles at the elevated temperatures. The coating microhardness increases a little with increasing the temperature to 350 ℃, and then decreases with further increasing temperature up to 950 ℃. This fact can be attributed to the microstructure evolution during the heat treatment.
基金Program for New Century Excellent Talents in University by the Ministry of Education of China(NECT-08-0463)the National Natural Science Foundation of China(51005180)the 111 Project(B08040)
文摘Numerical simulations focusing on the impacting behavior of cold sprayed particles were usually conducted by the Lagrangian formulation.However,the calculated outputs were much dependent on the meshing size owing to the excessive element distortion.Therefore,the Eulerian formulation becomes attractive,because it can avoid the extreme distortion of elements.In the present study,a copper particle impact on the same material substrate in cold spraying was simulated using the Eulerian formulation available in the ABAQUS software(Ver 6.8).The dependency of the calculated outputs on the meshing resolution were detailedly investigated.Results show that the meshing resolution not only has an effect on the shape of the deformed particle,but also it can significantly influence the maximum plastic strain and temperature under a given impact velocity.In addition,the copper particle deformation process at the critical velocity of 310 m/s shows that a jet composed of both of the particle and substrate materials can be formed and gets elongated with the impact time.
基金financially supported by National Natural Science Foundation of China (Grant Nos. 51690162, 51604171 and 51701112)China Postdoctoral Science Foundation (Grant Nos. 2017T100291 and 2017M611530)+1 种基金Shanghai Municipal Science and Technology Commission (No. 17JC1400602)open funding of State Key Laboratory of Solidification Processing in NWPU (SKLSP201602 and SKLSP201706)
文摘Effect of high static magnetic field on the dendritic morphology and growth direction in directionally solidified Al-10 wt.%Zn alloy were studied by three-dimensional(3D) X-ray micro-computed tomography, Electron Back-scattered Diffraction(EBSD) and X-ray Diffraction(XRD). The application of high static axial magnetic field(5T) during directional solidification was found to destabilize the solid/liquid interface and cause the growth direction of dendrite deviate from thermal gradient, leading to irregular solid/liquid interfacial shape and cellular to dendritic morphology transition. The thermoelectric magnetic convection(TEMC) caused by the interaction of thermoelectric effect and magnetic field was supposed to be responsible for the transition. In addition, the EBSD and XRD results confirm that the preferred growth direction of α-Al was found to transform from the traditionally expected <100> to<110>. The dendrite orientation transition(DOT) in Al-10 wt.%Zn alloy can be attributed to the effect of applied magnetic field on the anisotropy of crystal during solidification. The result indicates the potential application of high static magnetic field in altering the morphology and preferred growth direction of dendrite during directional solidification.
文摘Cold-sprayed magnesium coatings have been little researched although cold spraying has been applied to deposit a large number of materials such as metals,metal matrix composites.In the present study,helium gas and air were employed as the propelling gases to deposit Mg coatings under the temperature of 600℃and 630℃.The effect of gas types on the coating microstructure was investigated.It is much interesting to find that the particle deposition efficiency using helium gas as propelling gas is lower than that using air.This suggests that strong erosion occurred during cold spraying using helium gas.The porosity of the coating using helium gas is lower than that using air.In addition,the in-flight particle velocity was also simulated by the FLUENT software to explore the effect of gas types.The modeled results show that the in-flight particle velocity using helium is higher than the erosion velocity of Mg particle.
文摘Manufacturing of solid oxide fuel cell （SOFC） components remains nowadays a key point for the indus- trial development of this technology. Especially, the deposition of the dense electrolyte layer which is sand- wiched between the porous anode and the porous cathode is of paramount importance and thus focuses a lot of attention. Therefore, this paper considers and reviews recent developments concerning solid electrolyte layers manufacturing using thermal spray （TS） and physical vapour deposition （PVD） technologies.
基金Project(2012CB625100)supported by the National Basic Research Program of ChinaProject(2012AA03A512)supported by the National High-tech Research and Development Program of China
文摘A columnar Al film was firstly deposited on the top of 7%Y2O3？stabilized zirconia （7YSZ） ceramic coating in thermal barrier coating （TBC） system by magnetron sputtering. A vacuum treatment was then carried out at 700 °C for 1 h and 900 °C for 5 h to improve the erosion resistance of Al-deposited TBC. Aα-Al2O3 layer was in situ synthesized on the top of 7YSZ coating via vacuum heat treatment. The microstructure evolution of Al-deposited TBC illustrated that a loose surface-layer and a dense sub-layer formed on the top of 7YSZ coating after vacuum treatment. The phase structures of the as-sprayed TBC and the Al-deposited TBC after vacuum heat treatment were characterized by X-ray diffraction （XRD） and transmission electron microscope （TEM） assisted with focused ion beam （FIB）. Particulate erosion resistances of the as-sprayed TBC and treated TBC were compared at room temperature. In addition, erosion mechanism and schematic diagram were proposed. The results show that the Al-deposited TBC after vacuum heat treatment has better particulate erosion resistance than the as-sprayed one.
基金This work was supported by the National Key R&D Program of China,Grant No.2018YFA0306703.
文摘In order to realize a general-purpose automatic formal verification platform based on WebAssembly technology as a web service(FVPS),which aims to provide an automated report of vulnerability detections,this work builds a Hyperledger Fabric blockchain runtime model.It proposes an optimized methodology of the functional equivalent translation from source program languages to formal languages.This methodology utilizes an external application programming interface(API)table to replace the source codes in compilation,thereby pruning the part of housekeeping codes to ease code inflation.Code inflation is a significant metric in formal language translation.Namely,minor code inflation enhances verification scale and performance efficiency.It determines the efficiency of formal verification,involving launching,running,and memory usage.For instance,path explosion increases exponentially,resulting in out-of-memory.The experimental results conclude that program languages like golang severely impact code inflation.FVPS reduces the wasm code size by over 90%,achieving two orders of optimization magnitude,from 2000 kilobyte(KB)to 90 KB.That means we can cope with golang applications up to 20 times larger than the original in scale.This work eliminates the gap between Hyperledger Fabric smart contracts and WebAssembly.Our approach is pragmatic,adaptable,extendable,and flexible.Nowadays,FVPS is successfully applied in a Railway-Port-Aviation blockchain transportation system.
基金financially supported by the National Natural Science Foundation of China(No.51301112, No.51401129)Natural Science Foundation of Liaoning Province of China(No.201602553 )+1 种基金China Postdoctoral Science Foundation(2015M571327)The Science Research Program of Education Department in Liaoning Province(No.L2014048)
文摘Yttria-stabilized zirconia（ YSZ） coatings were deposited by low pressure plasma spray（ LPPS） in 1.0× 10^4 Pa,1.5 × 10^4 Pa,and 2.5 × 10^4 Pa. Both in-flight particle diagnostic detected by DPV-2000 system and ANSYS-FLUENT software were used to study the connection between the parameters of flying particles and the coating formation,which might help to recognize the relationship between the operation parameters and the coatings quality. The results of simulation showed that particles in a lower spray pressure could achieve a higher velocity. The particle velocity was around 380 m/s at a distance of 35 cm from the nozzle at 1.0 × 10^4 Pa while only 300 m/s at 2.5 × 10^4 Pa in actual measurement.The results showed that the velocity of particles increased with decreasing the spray pressure,which might enhance the flattening rate of coatings and thereby decreased the porosity. The deposited YSZ coating with the lowest porosity can be gained under 1.0 × 10^4 Pa condition.
