1.Introduction.Cold Spray(CS)is a highly advanced solid-state metal depo-sition process that was first developed in the 1980s.This innovative technique involves the high-speed(300-1200 m/s)impact deposition of micron-...1.Introduction.Cold Spray(CS)is a highly advanced solid-state metal depo-sition process that was first developed in the 1980s.This innovative technique involves the high-speed(300-1200 m/s)impact deposition of micron-sized particles(5-50μm)to fabricate coatings[1-3].CS has been extensively used in a variety of coating applications,such as aerospace,automotive,energy,medical,marine,and others,to provide protection against high temperatures,corrosion,erosion,oxidation,and chemicals[4,5].Nowadays,the technical interest in CS is twofold:(i)as a repair process for damaged components,and(ii)as a solid-state additive manufacturing process.Compared to other fusion-based additive manufacturing(AM)technologies,Cold Spray Additive Manufacturing(CSAM)is a new member of the AM family that can enable the fabrication of deposits without undergoing melting.The chemical composition has been largely preserved from the powder to the deposit due to the minimal oxidation.The significant advantages of CSAM over other additive manufacturing processes include a high production rate,unlimited deposition size,high flexibility,and suitability for repairing damaged parts.展开更多
Large interfacial strains in particles are crucial for promoting bonding in cold spraying(CS),initiated either by adiabatic shear instability(ASI)due to softening prevailing over strain hardening or by hydrostatic pla...Large interfacial strains in particles are crucial for promoting bonding in cold spraying(CS),initiated either by adiabatic shear instability(ASI)due to softening prevailing over strain hardening or by hydrostatic plasticity,which is claimed to promote bonding even without ASI.A thorough microstructural analysis is vital to fully understand the bonding mechanisms at play during microparticle impacts and throughout the CS process.In this study,the HEA CoCrFeMnNi,known for its relatively high strain hardening and resistance to softening,was selected to investigate the microstructure characteristics and bonding mech-anisms in CS.This study used characterization techniques covering a range of length scales,including electron channeling contrast imaging(ECCI),electron backscatter diffraction(EBSD),and high-resolution transmission microscopy(HR-TEM),to explore the microstructure characteristics of bonding and overall structure development of CoCrFeMnNi microparticles after impact in CS.HR-TEM lamellae were prepared using focused ion beam milling.Additionally,the effects of deformation field variables on microstructure development were determined through finite element modeling(FEM)of microparticle impacts.The ECCI,EBSD,and HR-TEM analyses revealed an interplay between dislocation-driven processes and twinning,leading to the development of four distinct deformation microstructures.Significant grain refinement occurs at the interface through continuous dynamic recrystallization(CDRX)due to high strain and temperature rise from adiabatic deformation,signs of softening,and ASI.Near the interface,a necklace-like structure of refined grains forms around grain boundaries,along with elongated grains,resulting from the coexistence of dynamic recovery and discontinuous dynamic recrystallization(DDRX)due to lower temperature rise and strain.Towards the particle or substrate interior,concurrent twinning and dislocation-mediated mechanisms refine the structure,forming straight,curved,and intersected twins.At the top of the particles,only deformed grains with a low dislocation density are observed.Our results showed that DRX induces microstructure softening in highly strained interface areas,facilitating atomic bonding in CoCrFeMnNi.HR-TEM investigation confirms the formation of atomic bonds between particles and substrate,with a gradual change in crystal lattice orientation from the particle to the substrate and the occurrence of some misfit dislocations and vacancies at the interface.Finally,the findings of this research suggest that softening and ASI,even in materials resistant to softening,are required to establish bonding in CS.展开更多
Cold spray(CS)has been attracting an increasing interest due to low heat input,which avoids grain growth and high thermal stress.This feature is beneficial for high damping Mn-Cu alloy through limiting oxidation and f...Cold spray(CS)has been attracting an increasing interest due to low heat input,which avoids grain growth and high thermal stress.This feature is beneficial for high damping Mn-Cu alloy through limiting oxidation and formation of hot cracks.However,high dislocation density formed because of extensive plastic deformation,pores,and cracks result in the low damping capacity in the as-deposited Mn-Cu alloy.New strategy was introduced for improving damping capacity in cold sprayed Mn-20Cu-5Ni-2Fe(M2052 at%)alloy with different particle sizes(below 25μm and between 15 and 53μm).The 15-53μm powder has high yield strength and plastic deformation resistance,which leads to a large number of defects and non-bonded interface between powders due to insufficient plastic deformation.Ageing treatment at 420℃leads to spinodal decomposition of the fcc-austenite,and the formation of Mn-rich matrix and Cu-rich nanoscale network structure is found.Under the same ageing conditions,the spinodal decomposition level of the fcc-austenite in the CS M2052 alloy with the particles of 15-53μm is higher than that with the particles of<25μm,which results from the difference in the grain size.As a result,the damping capacity in the CS M2052 samples with particle size of 15-53μm is higher compared with the CS M2052 sample with particle size of<25μm.There is a significant increase in the damping capacity in the CS M2052 samples after HIP treatment,which can effectively reduce the internal defects and improve the bonding properties between powders.展开更多
A Ti(Al,Si)3 diffusion coating was prepared on γ-TiAl alloy by cold sprayed Al?20Si alloy coating, followed by a heat-treatment. The isothermal and cyclic oxidation tests were conducted at 900 °C for 1000 h and ...A Ti(Al,Si)3 diffusion coating was prepared on γ-TiAl alloy by cold sprayed Al?20Si alloy coating, followed by a heat-treatment. The isothermal and cyclic oxidation tests were conducted at 900 °C for 1000 h and 120 cycles to check the oxidation resistance of the coating. The microstructure and phase transformation of the coating before and after the oxidation were studied by SEM, XRD and EPMA. The results indicate that the diffusion coating shows good oxidation resistance. The mass gain of the diffusion coating is only a quarter of that of bare alloy. After oxidation, the diffusion coating is degraded into three layers: an inner TiAl2 layer, a two-phase intermediate layer composed of a Ti(Al,Si)3 matrix and Si-rich precipitates, and a porous layer because of the inter-diffusion between the coating and substrate.展开更多
In this work,pure Cu with excellent strength and ductility(UTS of 271 MPa,elongation to fracture of 43.5%,uniform elongation of 30%)was prepared using cold spray additive manufacturing(CSAM),realizing a breakthrough i...In this work,pure Cu with excellent strength and ductility(UTS of 271 MPa,elongation to fracture of 43.5%,uniform elongation of 30%)was prepared using cold spray additive manufacturing(CSAM),realizing a breakthrough in the field.An in-depth investigation was conducted to reveal the microstructure evolution,strengthening and ductilization mechanisms of the CSAM Cu,as well as the single splats.The results show that the CSAM Cu possesses a unique heterogeneous microstructure with a bimodal grain structure and extensive infinitely circulating ring-mounted distribution of twinning.Based on the single splat observation,the entire copper particle forms a gradient nano-grained(GNG)structure after high-speed impact deposition.The GNG-structured single splat serves as a unit to build the heterogeneous microstructure with bimodal grain distribution during the successive deposition in CSAM.The results also show that CSAM can achieve synergistic strengthening and ductilization by controlling the grain refinement and dislocation density.This work provides potential for CSAM technique in manufacturing various metallic parts with the desired combination of high strength and good ductility without additional post-treatments.展开更多
Cold spray,as a solid-state additive manufacturing process,has been attracting increasing attention from both scientific and industrial communities.However,cold-sprayed deposits generally have unfavorable mechanical p...Cold spray,as a solid-state additive manufacturing process,has been attracting increasing attention from both scientific and industrial communities.However,cold-sprayed deposits generally have unfavorable mechanical properties in their as-fabricated state compared to conventionally manufactured and fusion-based additive-manufactured counterparts due to the inherent microstructural defects in the deposits(e.g.,porosity and incomplete interparticle bonding).This downside reduces its competitiveness and limits its wide applications as an additive manufacturing process.In the past years,many strengthening technologies have been developed or introduced to adjust the microstructure and improve the mechanical properties of cold-sprayed deposits.The term“strengthening”in this work specifically refers to improving the mechanical strength,particularly the tensile strength of the cold-sprayed bulk deposits.According to the stage that the strengthening technologies are used in the cold spray process,they can be classified into three categories:pre-process(e.g.,powder heat treatment),in-process(e.g.,powder heating,in-situ micro-forging,laser-assisted cold spray),and post-process(e.g.,post heat treatment,hot isostatic pressing,hot rolling,friction stir processing).Therefore,a comprehensive review of these strengthening technolo-gies is conducted to illuminate the possible correlations between the strengthening mechanisms and the resultant deposit microstructures and mechanical properties.This review paper aims to help researchers and engineers well understand the different strengthening methods and provide guidance for the cold spray community to develop new strengthening strategies for future high-quality mass production.展开更多
Potential engineering applications of magnesium(Mg)and Mg-based alloys,as the lightest structural metal,have made them a popular subject of study.However,the inferior corrosion and wear characteristics significantly l...Potential engineering applications of magnesium(Mg)and Mg-based alloys,as the lightest structural metal,have made them a popular subject of study.However,the inferior corrosion and wear characteristics significantly limit their application range.It is widely recognized that surface treatment is the most commonly utilized technique for remarkably improving a substrate’s surface characteristics.Numerous methods have been introduced for the surface treatment of Mg and Mg-based alloys to improve their corrosion behavior and tribological performance.Among these,thermal spray(TS)technology provides several methods for deposition of various functional metallic,ceramic,cermet,or other coatings tailored to particular conditions.Recent researches have shown the tremendous potential for thermal spray coated Mg alloys for biomedical and industrial applications.In this context,the cold spray(CS)method,as a comparatively new TS coating technique,can generate the coating layer using kinetic energy rather than combined thermal and kinetic energies,like the high-velocity oxy-fuel(HVOF)spray method.Moreover,the CS process,as a revolutionary method,is able to repair and refurbish with a faster turnaround time;it also provides solutions that do not require dealing with the thermal stresses that are part of the other repair processes,such as welding or other TS processes using a high-temperature flame.In this review paper,the recently designed coatings that are specifically applied to Mg alloys(primarily for industrial applications)employing various coating processes are reviewed.Because of the increased utilization of CS technology for both 3D printed(additively manufactured)coatings and repair of structurally critical components,the most recent CS methods for the surface treatment,repair,and refurbishment of Mg alloys as well as their benefits and restrictions are then discussed and reviewed in detail.Lastly,the prospects of this field of study are briefly discussed,along with a summary of the presented work.展开更多
In this work,the Invar 36 alloys were manufactured using cold spray(CS)additive manufacturing technique.The systematic investigations were made on the microstructural evolution,thermal expansion and mechanical propert...In this work,the Invar 36 alloys were manufactured using cold spray(CS)additive manufacturing technique.The systematic investigations were made on the microstructural evolution,thermal expansion and mechanical properties under as-sprayed(AS)and heat-treated(HT)conditions.XRD(X-ray diffraction)and ICP-AES(inductively coupled plasma atomic emission spectroscopy)analyses show that no phase transformation,oxidation,nor element content change have occurred.The X-ray computed tomography(XCT)exhibited a near fully dense structure with a porosity of 0.025%in the helium-produced sample under as-sprayed condition,whereas the nitrogen-produced samples produced at 5 MPa and 800℃show more irregular pore defects.He-AS sample shows a more prominent grain refinement than that of nitrogen samples due to the more extensive plastic deformation.The post heat-treatment exhibited a promoted grain growth,inter-particle diffusion,as well as the formation of annealing twins.Between25℃and 200℃,the nitrogen samples possessed lower CTE(coefficient of thermal expansion)values(1.53×10^(-6)/℃)compared with those produced by casting and laser additive manufacturing.The He-AS samples exhibited a noticeable negative CTE value between 25℃and 200℃,which may due to the significant compressive residual stress(-272 MPa)compensating its displacement with temperature increase during CTE test.The N2-HT and He-HT Invar 36 samples present a notable balance between strength and ductility.In conclusion,the CS technique can be considered as a potential method to produce the Invar36 component with high thermal and mechanical performance.展开更多
In this study,three kinds of A380/Al2O3 composite coatings were prepared by cold spray(CS)using spherical,irregular and spherical+irregular shaped Al2O3 particulates separately mixed in the original A380 alloy powders...In this study,three kinds of A380/Al2O3 composite coatings were prepared by cold spray(CS)using spherical,irregular and spherical+irregular shaped Al2O3 particulates separately mixed in the original A380 alloy powders.The influence of Al2O3 particulates’morphology on the microstructural characteristics(i.e.retention of Al2O3 content in coatings,coating/matrix interfacial bonding,pore size distribution and morphology etc.)and wear performance of the coatings was investigated by scanning electron microscopy(SEM),X-ray computed tomography(XCT)and 3-D optical profilometry.Results indicated that the spherical Al2O3 showsobvious tamping effect during deposition process.As a result,the interfaceshowedawavy shape while the matrix and particulates were mechanical interlocked with much improved adhesion.In addition,the porosity of the coating was minimized and the pores exhibited curved spherical structure with reduced dimensions.The irregular Al2O3 particles predominantly displayed the embedding effect together with fragmentation of Al2O3 particulates.Consequently,poor coating/matrix interfacial bonding,high porosity and the formation of angular-shaped pores were resulted in the coating.Dry sliding wear tests results revealed that the wear resistance of the coating is directly related with the retained content of Al2O3 in the coating.The coating containing irregular Al2O3 particulates displayed superior wear performance with its wear rate one seventh of that of the pure A380 alloy coating.The coating containing both kinds of Al2O3 particulates showed mixed characteristics of above two kinds of Al2O3 composite coatings.展开更多
In this study,the effects of annealing and solution aging heat treatment on the microstructure and mechanical properties of cold spray additive manufactured(CSAMed)AA2024/Al_(2)O_(3) composite were investigated.The re...In this study,the effects of annealing and solution aging heat treatment on the microstructure and mechanical properties of cold spray additive manufactured(CSAMed)AA2024/Al_(2)O_(3) composite were investigated.The results showed that both annealing and solution aging enhanced the interfacial bonding between the deposited AA2024 particles in the composite.The tensile properties of CSAMed AA2024/Al_(2)O_(3) composite were significantly improved by 13.8%for ultimate tensile strength and 47.8%for elongation after solution aging.Microstructural examination and fractographic analysis showed that the fracture mechanism between the adjacent AA2024 particles changed from brittle to ductile-dominant mode after heat treatment.However,the interfacial bonding between the AA2024 and Al_(2)O_(3) particles cannot be improved.For the improvement of mechanical properties,the solution aging was slightly better than annealing.In addition,low-temperature annealing greatly reduced the anisotropy of the mechanical properties of CSAMed AA2024/Al_(2)O_(3) composite.展开更多
This work focused on the role of Al_(2)O_(3) particles in the corrosion behavior of cold sprayed AA5083 aluminum alloy matrix composite(Al-MMC)coatings.The electrochemical characterization of the coatings was investig...This work focused on the role of Al_(2)O_(3) particles in the corrosion behavior of cold sprayed AA5083 aluminum alloy matrix composite(Al-MMC)coatings.The electrochemical characterization of the coatings was investigated in a 3.5 wt.%NaCl solution as a function of time.The results show that fragmentation of Al_(2)O_(3) particles is not clearly observed in the case of AA5083/20 vol.%Al_(2)O_(3) coating,while the broken Al_(2)O_(3) particles can be seen clearly in AA5083/40 vol.%Al_(2)O_(3) and AA5083/60 vol.%Al_(2)O_(3) coatings.The addition of 20 vol.%Al_(2)O_(3) particles yield the coating with the lowest porosity,and different volume fractions of Al_(2)O_(3)in the feedstock have important effects on the electrochemical behavior of composite coatings.The Al-MMC coating reinforced with 20 vol.%Al_(2)O_(3) particles exhibits the highest Ecorrand the lowest icorrcompared with the other conditions.The order of current density is as follows:AA5083/20vol.%Al_(2)O_(3)<AA5083<AA5083/40 vol.%Al_(2)O_(3)<AA5083/60 vol.%Al_(2)O_(3).展开更多
The oxide scale present on the feedstock particles is critical for inter-particle bond formation in the cold spray(CS)coating process,therefore,oxide scale break-up is a prerequisite for clean metallic contact which g...The oxide scale present on the feedstock particles is critical for inter-particle bond formation in the cold spray(CS)coating process,therefore,oxide scale break-up is a prerequisite for clean metallic contact which greatly improves the quality of inter-particle bonding within the deposited coating.In general,a spray powder which contains a thicker oxide scale on its surface(i.e.,powders having high oxygen content)requires a higher critical particle velocity for coating formation,which also lowers the deposition efficiency(DE)making the whole process a challenging task.In this work,it is reported for the first time that an artificially oxidized copper(Cu)powder containing a high oxygen content of 0.81 wt.%with a thick surface oxide scale of 0.71μm.,can help achieve an astonishing increment in DE.A transition of surficial oxide scale evolution starting with crack initiations followed by segmenting to peeling-off was observed during the high velocity particle impact of the particles,which helps in achieving an astounding increment in DE.Single-particle deposit observations revealed that the thick oxide scale peels off from most of the sprayed powder surfaces during the high-velocity impact,which leaves a clean metallic surface on the deposited particle.This makes the successive particles to bond easily and thus leads to a higher DE.Further,owning to the peeling-off of the oxide scale from the feedstock particles,very few discontinuous oxide scale segments are retained at inter-particle boundaries ensuring a high electrical conductivity within the resulting deposit.Dependency of the oxide scale threshold thickness for peeling-off during the high velocity particle impact was also investigated.展开更多
In the present study, 304 stainless steel coatings were deposited on interstitial-free steel substrates by cold gas dynamic spray technology. The effect of gas temperature on microstructure, micro-hardness, cohesive s...In the present study, 304 stainless steel coatings were deposited on interstitial-free steel substrates by cold gas dynamic spray technology. The effect of gas temperature on microstructure, micro-hardness, cohesive strength, and electrochemical property of the coatings were investigated and compared. The results showed that increasing gas temperature had a great contribution to enhancing the bonding strength between the deposited particles and making the microstructure more density. Therefore, the porosity of the coatings decreased from 0%4-0.5% to 2%4-0.3%, and the tensile strength of the coatings increased from 564-4 MPa up to 734-3 MPa. In addition, the corrosion resistance of the coatings was also deeply influenced by process gas temperature. The corrosion kinetics of the coatings were affected by both of the plastic deformation of deposited particles and the porosity in the coatings.展开更多
Cold spray is an attractive and rapidly developing process for additive manufacturing with high efficiency and precision,repairing and coating,especially in aircraft and aerospace applications.Cold spray additive manu...Cold spray is an attractive and rapidly developing process for additive manufacturing with high efficiency and precision,repairing and coating,especially in aircraft and aerospace applications.Cold spray additive manufacturing deposits micro-particles with large plastic deformation below their melting point,eliminating heat effect zone which could deteriorate the quality of repairing zone.The particle deposition in cold spray is a complex process which involves high strain rate,high contact pressure and high temperature.Here we develop,utilize and validate a thermomechanical model to provide a definitive way to predict deposition mechanics and surface deformation evolution for particle deposition process in cold spray additive manufacturing.Both a single particle and dual particles models were developed to investigate the contact interaction between particle/substrate and particle/particle.Different combinations of particle/substrate materials(Cu/Cu,Al/Al,steel/steel,and nickel/nickel)and process parameters were considered in this study.The experimental study was conducted to validate simulation results,providing useful information for understanding the limitations and challenges associated with cold spray additive manufacturing.The framework provides insights into improving the quality and precision of stress/strain formation,particle interactions and particle deposition in cold spray additive manufacturing process.展开更多
Cold spray(CS)which has recently become a promising additive manufacturing(AM)technology,was used to fabricate ultra-strong pure copper.In addition,the effects of carrier gas species on the microstructural characteris...Cold spray(CS)which has recently become a promising additive manufacturing(AM)technology,was used to fabricate ultra-strong pure copper.In addition,the effects of carrier gas species on the microstructural characteristics,mechanical properties and deformation mechanisms were systemically explored.The CSAM copper manufactured with N_(2) carrier gas reveals a heterogeneous bimodal microstructure consisting of ultra-fine grains at the particle interface and relatively coarse grains in inner particles.With He carrier gas,a homogeneous grain structure consisting of ultra-fine grains in most areas was obtained.Compressive tests showed that N_(2) and He carrier gasses enabled ultra-high yield strengths of 340 and415 MPa,respectively.These values are comparable to severely plastic deformed copper,which has extremely low ductility and shape fidelity.On the other hand,both samples showed a strain-softening phenomenon that does not commonly occur at room temperature.The deformation microstructures revealed that dynamic recovery(DRV)and dynamic recrystallization(DRX)phenomena were generated despite being deformed at room temperature.Based on the above findings,the overall deformation mechanisms according to the carrier gas species in the CSAM copper manufacturing process were discussed.Furthermore,the work hardening and softening behaviors of CSAM Cu are predicted by using a constitutive equation.展开更多
In this study, an innovative approach was used to fabricate Ti–Ta composite biomaterials through cold spray additive manufacturing followed by a diff usion treatment. The microstructure and mechanical properties of t...In this study, an innovative approach was used to fabricate Ti–Ta composite biomaterials through cold spray additive manufacturing followed by a diff usion treatment. The microstructure and mechanical properties of the composites were investigated in detail using field emission scanning electron microscopy, electron backscatter diff raction, 3D X-ray computed tomography, tensile test, nanohardness test and resonance vibration test. The obtained results indicated that the prepared composites have inhomogeneity in their microstructure and composition. A unique microstructure, composed of Ti-rich, Ta-rich and diff usion regions, was evolved in the composites due to incomplete diff usion between Ti and Ta splats. Further, Kirkendall pores were formed in the composites due to uneven diff usion of the two phases(of Ti and Ta) during high-temperature heat treatment. The prepared composites simultaneously showed low elastic modulus and high tensile strength which is required for a good biomaterial. Low elastic modulus was associated with the residual pores and the alloying eff ect of Ta in Ti, while high tensile strength was related to the solid solution strengthening eff ects. The obtained results indicated that the prepared Ti–Ta composites have a great potential to become a new candidate for biomedical applications.展开更多
Particles may rebound from a substrate surface during cold spraying, which affects the quality of the coating. In this paper, the rebound phenomenon and its consequences on deposition behavior have been analyzed using...Particles may rebound from a substrate surface during cold spraying, which affects the quality of the coating. In this paper, the rebound phenomenon and its consequences on deposition behavior have been analyzed using the finite element analysis software ANSYS/LS-DYNA version 970. In a range of particle velocities of 50-1000 m/s, increases of the impact velocity caused a rapid decline of the rebound coefficient R to a low point Rmin. After that, R began to rise slowly. Then the effect of the impact velocities and material properties on the rebound phenomenon were analyzed. Both the material strength and density influenced this rebound phenomenon. Four stages of the impact process and a model of strain distribution were proposed in detail to explain the rebound phenomenon.展开更多
The particle acceleration behavior and deposition mechanism of cold spraying aluminum matrix composites(Al_(2)O_(3)/2024)are complicated by the addition of ceramic particles.The effects of different feeding rates and ...The particle acceleration behavior and deposition mechanism of cold spraying aluminum matrix composites(Al_(2)O_(3)/2024)are complicated by the addition of ceramic particles.The effects of different feeding rates and particle diameters on critical velocity and mechanical properties were studied by numerical simulation and experiment.The results indicate that as the powder feeding rate increases,the impact velocity of gas and particles gradually decreases,and the temperature of gas and particles increases,resulting in an increase in the difference between particle impact velocity and critical velocity.The highest tensile strength of the deposit is achieved at a powder feeding rate of 1 r/min,which is 343 MPa.As the powder feeding rate increases,the performance of the deposits decreases,but it significantly saves time and cost.As the particle diameter increases,the impact temperature first increases and then decreases,resulting in the critical velocity first decreasing and then increasing,and the mechanical performance first increasing and then decreasing.To some extent,the best performance of the deposit is achieved when the size of the metal particle is close to that of the ceramic particle.展开更多
Cold spray(CS) is considered as a new type of repairing technique for restoration or remanufacturing of a wide range of unserviceable engineering components due to its unique ‘cold’ characteristic. In this work, a v...Cold spray(CS) is considered as a new type of repairing technique for restoration or remanufacturing of a wide range of unserviceable engineering components due to its unique ‘cold’ characteristic. In this work, a viable repairing approach i.e. "cold spraying followed by hot rolling post-treatment" was successfully applied to restore defective neutron shielding B_(4)C/6061 Al composite plates. Scanning electron microscopy(SEM) and electron backscatter diffraction(EBSD) results revealed that the coating-substrate interface is in a good bonding state without micro-cracks. Hot rolling post-treatment resulted in improved microstructure of the as-sprayed deposit with more uniform distribution of B_(4)C particles in the matrix.Moreover, well bonded splat boundaries and strain free Al grains were evolved in the matrix due to enhanced splat deformation and continuous dynamic recrystallization(CDRX). Three-point bending test results revealed that the strength of the repaired material is at par with the in-service plates. The findings of this work could be considered as a great stride to further extend possible applications of CS for repairing engineering structural components.展开更多
Cold spraying is a new coating process and manufacturing technology.The coating quality is upgraded with dense layers,higher bonding force and lower oxidation comparing with thermal spraying.Bonding of particles onto ...Cold spraying is a new coating process and manufacturing technology.The coating quality is upgraded with dense layers,higher bonding force and lower oxidation comparing with thermal spraying.Bonding of particles onto substrate is a result of extensive plastic deformation and related phenomena at the interface.The cold-sprayed copper and aluminum deposits on aluminum and steel substrates were prepared,and the features of interface were observed by using scanning electron microscope(SEM).Then the particle/substrate impact process was modeling through finite-element methods(ANSYS/LS-DYNA software).Numerical results show that the high plastic strain at the interface can result in an adiabatic shear instability at the interface.Due to these extremely high pressure and strain rate,it may be more appropriate to treat the material adjacent to the particle/substrate interface as a viscous‘fluid-like’material,various fluid-based phenomena,such as interfacial instabilities and roll-ups and vortices,can lead to interface material mixing.In numerical simulation,adiabatic shear instability both in the particle and the substrate at contact interface is regarded as a criterion for predicting the optimal process parameters and the bonding feature.展开更多
基金supported by the National Natural Science Foundation of China(No.52061135101 and 52001078)the German Research Foundation(DFG,No.448318292)+3 种基金the Technology Innovation Guidance Special Foundation of Shaanxi Province(No.2023GXLH-085)the Fundamental Research Funds for the Central Universities(No.D5000240161)the Project of Key areas of innovation team in Shaanxi Province(No.2024RS-CXTD-20)The author Yingchun Xie thanks the support from the National Key R&D Program(No.2023YFE0108000).
文摘1.Introduction.Cold Spray(CS)is a highly advanced solid-state metal depo-sition process that was first developed in the 1980s.This innovative technique involves the high-speed(300-1200 m/s)impact deposition of micron-sized particles(5-50μm)to fabricate coatings[1-3].CS has been extensively used in a variety of coating applications,such as aerospace,automotive,energy,medical,marine,and others,to provide protection against high temperatures,corrosion,erosion,oxidation,and chemicals[4,5].Nowadays,the technical interest in CS is twofold:(i)as a repair process for damaged components,and(ii)as a solid-state additive manufacturing process.Compared to other fusion-based additive manufacturing(AM)technologies,Cold Spray Additive Manufacturing(CSAM)is a new member of the AM family that can enable the fabrication of deposits without undergoing melting.The chemical composition has been largely preserved from the powder to the deposit due to the minimal oxidation.The significant advantages of CSAM over other additive manufacturing processes include a high production rate,unlimited deposition size,high flexibility,and suitability for repairing damaged parts.
文摘Large interfacial strains in particles are crucial for promoting bonding in cold spraying(CS),initiated either by adiabatic shear instability(ASI)due to softening prevailing over strain hardening or by hydrostatic plasticity,which is claimed to promote bonding even without ASI.A thorough microstructural analysis is vital to fully understand the bonding mechanisms at play during microparticle impacts and throughout the CS process.In this study,the HEA CoCrFeMnNi,known for its relatively high strain hardening and resistance to softening,was selected to investigate the microstructure characteristics and bonding mech-anisms in CS.This study used characterization techniques covering a range of length scales,including electron channeling contrast imaging(ECCI),electron backscatter diffraction(EBSD),and high-resolution transmission microscopy(HR-TEM),to explore the microstructure characteristics of bonding and overall structure development of CoCrFeMnNi microparticles after impact in CS.HR-TEM lamellae were prepared using focused ion beam milling.Additionally,the effects of deformation field variables on microstructure development were determined through finite element modeling(FEM)of microparticle impacts.The ECCI,EBSD,and HR-TEM analyses revealed an interplay between dislocation-driven processes and twinning,leading to the development of four distinct deformation microstructures.Significant grain refinement occurs at the interface through continuous dynamic recrystallization(CDRX)due to high strain and temperature rise from adiabatic deformation,signs of softening,and ASI.Near the interface,a necklace-like structure of refined grains forms around grain boundaries,along with elongated grains,resulting from the coexistence of dynamic recovery and discontinuous dynamic recrystallization(DDRX)due to lower temperature rise and strain.Towards the particle or substrate interior,concurrent twinning and dislocation-mediated mechanisms refine the structure,forming straight,curved,and intersected twins.At the top of the particles,only deformed grains with a low dislocation density are observed.Our results showed that DRX induces microstructure softening in highly strained interface areas,facilitating atomic bonding in CoCrFeMnNi.HR-TEM investigation confirms the formation of atomic bonds between particles and substrate,with a gradual change in crystal lattice orientation from the particle to the substrate and the occurrence of some misfit dislocations and vacancies at the interface.Finally,the findings of this research suggest that softening and ASI,even in materials resistant to softening,are required to establish bonding in CS.
基金supported by Guangdong Natural Science Foundation(No.2024A1515011287)Guangdong Academy of Sciences Project(No.2021GDASYL-20210102002)+2 种基金GDAS’Project of Science and Technology Development(Nos.2022GDASZH-2022010103 and 2022GDASZH-2022010202-04)GuangDong Province Key-Area R&D Program(No.2020B0101340004)the Ministry of Science and Higher Education of the Russian Federation within the framework of the“World-class Science Center”program:Advanced Digital Technologies(No.075-15-2022-312 from 20 April 2022).
文摘Cold spray(CS)has been attracting an increasing interest due to low heat input,which avoids grain growth and high thermal stress.This feature is beneficial for high damping Mn-Cu alloy through limiting oxidation and formation of hot cracks.However,high dislocation density formed because of extensive plastic deformation,pores,and cracks result in the low damping capacity in the as-deposited Mn-Cu alloy.New strategy was introduced for improving damping capacity in cold sprayed Mn-20Cu-5Ni-2Fe(M2052 at%)alloy with different particle sizes(below 25μm and between 15 and 53μm).The 15-53μm powder has high yield strength and plastic deformation resistance,which leads to a large number of defects and non-bonded interface between powders due to insufficient plastic deformation.Ageing treatment at 420℃leads to spinodal decomposition of the fcc-austenite,and the formation of Mn-rich matrix and Cu-rich nanoscale network structure is found.Under the same ageing conditions,the spinodal decomposition level of the fcc-austenite in the CS M2052 alloy with the particles of 15-53μm is higher than that with the particles of<25μm,which results from the difference in the grain size.As a result,the damping capacity in the CS M2052 samples with particle size of 15-53μm is higher compared with the CS M2052 sample with particle size of<25μm.There is a significant increase in the damping capacity in the CS M2052 samples after HIP treatment,which can effectively reduce the internal defects and improve the bonding properties between powders.
基金Project(50971127)supported by the National Natural Science Foundation of China
文摘A Ti(Al,Si)3 diffusion coating was prepared on γ-TiAl alloy by cold sprayed Al?20Si alloy coating, followed by a heat-treatment. The isothermal and cyclic oxidation tests were conducted at 900 °C for 1000 h and 120 cycles to check the oxidation resistance of the coating. The microstructure and phase transformation of the coating before and after the oxidation were studied by SEM, XRD and EPMA. The results indicate that the diffusion coating shows good oxidation resistance. The mass gain of the diffusion coating is only a quarter of that of bare alloy. After oxidation, the diffusion coating is degraded into three layers: an inner TiAl2 layer, a two-phase intermediate layer composed of a Ti(Al,Si)3 matrix and Si-rich precipitates, and a porous layer because of the inter-diffusion between the coating and substrate.
基金the National Natural Science Foundation of China(Nos.52001191,52001078,52061135101)the Shanghai Science and Technology Committee(No.20511107700)+5 种基金Shanghai“Shuguang Program”(No.20SG42)Shanghai Rising-Star Program(No.20QA1403800)Key-Area Research and Development Program of Guangdong Province of China(No.2020B0101330001)Guangzhou Science and Technology Program of China(No.202007020008)the Research Fund of the State Key Laboratory of Solidification Processing(NPU,China)(No.2022-TZ-01)the Guangdong Provincial Key Laboratory of Modern Surface Engineering Technology and the Institute of New Materials,Guangdong Academy of Sciences(No.2020B1212060049).
文摘In this work,pure Cu with excellent strength and ductility(UTS of 271 MPa,elongation to fracture of 43.5%,uniform elongation of 30%)was prepared using cold spray additive manufacturing(CSAM),realizing a breakthrough in the field.An in-depth investigation was conducted to reveal the microstructure evolution,strengthening and ductilization mechanisms of the CSAM Cu,as well as the single splats.The results show that the CSAM Cu possesses a unique heterogeneous microstructure with a bimodal grain structure and extensive infinitely circulating ring-mounted distribution of twinning.Based on the single splat observation,the entire copper particle forms a gradient nano-grained(GNG)structure after high-speed impact deposition.The GNG-structured single splat serves as a unit to build the heterogeneous microstructure with bimodal grain distribution during the successive deposition in CSAM.The results also show that CSAM can achieve synergistic strengthening and ductilization by controlling the grain refinement and dislocation density.This work provides potential for CSAM technique in manufacturing various metallic parts with the desired combination of high strength and good ductility without additional post-treatments.
基金the financial support from the following funding agency and projects:Science Foundation Ireland Frontiers for the Future Project(No.20/FFP-P/8815)National Natural Science Foundation of China(Nos.51875471,52001078,and 52061135101)+2 种基金China Scholarship Council-Trinity College Dublin Joint Scholarship Programme(No.201906460020)International Cooperation Project of Guangdong Province(No.2021A0505030052)Alexander von Humboldt Foundation.
文摘Cold spray,as a solid-state additive manufacturing process,has been attracting increasing attention from both scientific and industrial communities.However,cold-sprayed deposits generally have unfavorable mechanical properties in their as-fabricated state compared to conventionally manufactured and fusion-based additive-manufactured counterparts due to the inherent microstructural defects in the deposits(e.g.,porosity and incomplete interparticle bonding).This downside reduces its competitiveness and limits its wide applications as an additive manufacturing process.In the past years,many strengthening technologies have been developed or introduced to adjust the microstructure and improve the mechanical properties of cold-sprayed deposits.The term“strengthening”in this work specifically refers to improving the mechanical strength,particularly the tensile strength of the cold-sprayed bulk deposits.According to the stage that the strengthening technologies are used in the cold spray process,they can be classified into three categories:pre-process(e.g.,powder heat treatment),in-process(e.g.,powder heating,in-situ micro-forging,laser-assisted cold spray),and post-process(e.g.,post heat treatment,hot isostatic pressing,hot rolling,friction stir processing).Therefore,a comprehensive review of these strengthening technolo-gies is conducted to illuminate the possible correlations between the strengthening mechanisms and the resultant deposit microstructures and mechanical properties.This review paper aims to help researchers and engineers well understand the different strengthening methods and provide guidance for the cold spray community to develop new strengthening strategies for future high-quality mass production.
文摘Potential engineering applications of magnesium(Mg)and Mg-based alloys,as the lightest structural metal,have made them a popular subject of study.However,the inferior corrosion and wear characteristics significantly limit their application range.It is widely recognized that surface treatment is the most commonly utilized technique for remarkably improving a substrate’s surface characteristics.Numerous methods have been introduced for the surface treatment of Mg and Mg-based alloys to improve their corrosion behavior and tribological performance.Among these,thermal spray(TS)technology provides several methods for deposition of various functional metallic,ceramic,cermet,or other coatings tailored to particular conditions.Recent researches have shown the tremendous potential for thermal spray coated Mg alloys for biomedical and industrial applications.In this context,the cold spray(CS)method,as a comparatively new TS coating technique,can generate the coating layer using kinetic energy rather than combined thermal and kinetic energies,like the high-velocity oxy-fuel(HVOF)spray method.Moreover,the CS process,as a revolutionary method,is able to repair and refurbish with a faster turnaround time;it also provides solutions that do not require dealing with the thermal stresses that are part of the other repair processes,such as welding or other TS processes using a high-temperature flame.In this review paper,the recently designed coatings that are specifically applied to Mg alloys(primarily for industrial applications)employing various coating processes are reviewed.Because of the increased utilization of CS technology for both 3D printed(additively manufactured)coatings and repair of structurally critical components,the most recent CS methods for the surface treatment,repair,and refurbishment of Mg alloys as well as their benefits and restrictions are then discussed and reviewed in detail.Lastly,the prospects of this field of study are briefly discussed,along with a summary of the presented work.
基金supported financially by the National Key Research and Development Program of China(No.2019YFA0705300)the Guangdong Special Support Program(No.2019BT02C629)+6 种基金the National Natural Science Foundation of China(No.51690160)the Shanghai Science and Technology Committee(No.19DZ1100704)the Shanghai Sailing Program(No.19YF1415900)Golden Apple Project of Baosteel Co.,Ltd(No.A19EC13500)the Guangdong Basic and Applied Basic Research Foundation(No.2019B1515120016)the Guangzhou Science and Technology Program(Nos.202002030290 and 202007020008)the GDAS’Project of Science and Technology Development(Nos.2019GDASYL-0503006 and 2020GDASYL-20200302011)。
文摘In this work,the Invar 36 alloys were manufactured using cold spray(CS)additive manufacturing technique.The systematic investigations were made on the microstructural evolution,thermal expansion and mechanical properties under as-sprayed(AS)and heat-treated(HT)conditions.XRD(X-ray diffraction)and ICP-AES(inductively coupled plasma atomic emission spectroscopy)analyses show that no phase transformation,oxidation,nor element content change have occurred.The X-ray computed tomography(XCT)exhibited a near fully dense structure with a porosity of 0.025%in the helium-produced sample under as-sprayed condition,whereas the nitrogen-produced samples produced at 5 MPa and 800℃show more irregular pore defects.He-AS sample shows a more prominent grain refinement than that of nitrogen samples due to the more extensive plastic deformation.The post heat-treatment exhibited a promoted grain growth,inter-particle diffusion,as well as the formation of annealing twins.Between25℃and 200℃,the nitrogen samples possessed lower CTE(coefficient of thermal expansion)values(1.53×10^(-6)/℃)compared with those produced by casting and laser additive manufacturing.The He-AS samples exhibited a noticeable negative CTE value between 25℃and 200℃,which may due to the significant compressive residual stress(-272 MPa)compensating its displacement with temperature increase during CTE test.The N2-HT and He-HT Invar 36 samples present a notable balance between strength and ductility.In conclusion,the CS technique can be considered as a potential method to produce the Invar36 component with high thermal and mechanical performance.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51671205 and 51801217).
文摘In this study,three kinds of A380/Al2O3 composite coatings were prepared by cold spray(CS)using spherical,irregular and spherical+irregular shaped Al2O3 particulates separately mixed in the original A380 alloy powders.The influence of Al2O3 particulates’morphology on the microstructural characteristics(i.e.retention of Al2O3 content in coatings,coating/matrix interfacial bonding,pore size distribution and morphology etc.)and wear performance of the coatings was investigated by scanning electron microscopy(SEM),X-ray computed tomography(XCT)and 3-D optical profilometry.Results indicated that the spherical Al2O3 showsobvious tamping effect during deposition process.As a result,the interfaceshowedawavy shape while the matrix and particulates were mechanical interlocked with much improved adhesion.In addition,the porosity of the coating was minimized and the pores exhibited curved spherical structure with reduced dimensions.The irregular Al2O3 particles predominantly displayed the embedding effect together with fragmentation of Al2O3 particulates.Consequently,poor coating/matrix interfacial bonding,high porosity and the formation of angular-shaped pores were resulted in the coating.Dry sliding wear tests results revealed that the wear resistance of the coating is directly related with the retained content of Al2O3 in the coating.The coating containing irregular Al2O3 particulates displayed superior wear performance with its wear rate one seventh of that of the pure A380 alloy coating.The coating containing both kinds of Al2O3 particulates showed mixed characteristics of above two kinds of Al2O3 composite coatings.
基金supported by the National Natural Science Foundation of China (No.51875471)the Research Fund of the State Key Laboratory of Solidification Processing (NPU),China (No.2021TZ-01)。
文摘In this study,the effects of annealing and solution aging heat treatment on the microstructure and mechanical properties of cold spray additive manufactured(CSAMed)AA2024/Al_(2)O_(3) composite were investigated.The results showed that both annealing and solution aging enhanced the interfacial bonding between the deposited AA2024 particles in the composite.The tensile properties of CSAMed AA2024/Al_(2)O_(3) composite were significantly improved by 13.8%for ultimate tensile strength and 47.8%for elongation after solution aging.Microstructural examination and fractographic analysis showed that the fracture mechanism between the adjacent AA2024 particles changed from brittle to ductile-dominant mode after heat treatment.However,the interfacial bonding between the AA2024 and Al_(2)O_(3) particles cannot be improved.For the improvement of mechanical properties,the solution aging was slightly better than annealing.In addition,low-temperature annealing greatly reduced the anisotropy of the mechanical properties of CSAMed AA2024/Al_(2)O_(3) composite.
基金financially supported by the authors would like to acknowledge the National Key Research and Development Program of China(No.2016YFB1100104)the National Natural Science Foundation of China(No.51875470)+1 种基金the State Key Laboratory of Solidification Processing(NPU,China)(No.2019-QZ-01)the financial support from the fund of SAST(No.SAST2016043)。
文摘This work focused on the role of Al_(2)O_(3) particles in the corrosion behavior of cold sprayed AA5083 aluminum alloy matrix composite(Al-MMC)coatings.The electrochemical characterization of the coatings was investigated in a 3.5 wt.%NaCl solution as a function of time.The results show that fragmentation of Al_(2)O_(3) particles is not clearly observed in the case of AA5083/20 vol.%Al_(2)O_(3) coating,while the broken Al_(2)O_(3) particles can be seen clearly in AA5083/40 vol.%Al_(2)O_(3) and AA5083/60 vol.%Al_(2)O_(3) coatings.The addition of 20 vol.%Al_(2)O_(3) particles yield the coating with the lowest porosity,and different volume fractions of Al_(2)O_(3)in the feedstock have important effects on the electrochemical behavior of composite coatings.The Al-MMC coating reinforced with 20 vol.%Al_(2)O_(3) particles exhibits the highest Ecorrand the lowest icorrcompared with the other conditions.The order of current density is as follows:AA5083/20vol.%Al_(2)O_(3)<AA5083<AA5083/40 vol.%Al_(2)O_(3)<AA5083/60 vol.%Al_(2)O_(3).
基金supported financially by the National Natural Science Foundation of China(No.51875443)the Guangdong Basic and Applied Basic Research Foundation(Nos.2019B1515120016 and 202002030290)+3 种基金the Shaanxi Co-Innovation Projects(No.2015KTTSGY03-03)the Shaanxi Natural Science Foundation(No.2015JQ5200)the Open Project from The Key Lab of Guangdong for Modern Surface Engineering Technologyfinancial support by Guangdong Academy of Sciences’Project of Constructing First-class Domestic Research Institutions(Nos.2019GDASYL-0503006,2020GDASYL-20200302011)。
文摘The oxide scale present on the feedstock particles is critical for inter-particle bond formation in the cold spray(CS)coating process,therefore,oxide scale break-up is a prerequisite for clean metallic contact which greatly improves the quality of inter-particle bonding within the deposited coating.In general,a spray powder which contains a thicker oxide scale on its surface(i.e.,powders having high oxygen content)requires a higher critical particle velocity for coating formation,which also lowers the deposition efficiency(DE)making the whole process a challenging task.In this work,it is reported for the first time that an artificially oxidized copper(Cu)powder containing a high oxygen content of 0.81 wt.%with a thick surface oxide scale of 0.71μm.,can help achieve an astonishing increment in DE.A transition of surficial oxide scale evolution starting with crack initiations followed by segmenting to peeling-off was observed during the high velocity particle impact of the particles,which helps in achieving an astounding increment in DE.Single-particle deposit observations revealed that the thick oxide scale peels off from most of the sprayed powder surfaces during the high-velocity impact,which leaves a clean metallic surface on the deposited particle.This makes the successive particles to bond easily and thus leads to a higher DE.Further,owning to the peeling-off of the oxide scale from the feedstock particles,very few discontinuous oxide scale segments are retained at inter-particle boundaries ensuring a high electrical conductivity within the resulting deposit.Dependency of the oxide scale threshold thickness for peeling-off during the high velocity particle impact was also investigated.
文摘In the present study, 304 stainless steel coatings were deposited on interstitial-free steel substrates by cold gas dynamic spray technology. The effect of gas temperature on microstructure, micro-hardness, cohesive strength, and electrochemical property of the coatings were investigated and compared. The results showed that increasing gas temperature had a great contribution to enhancing the bonding strength between the deposited particles and making the microstructure more density. Therefore, the porosity of the coatings decreased from 0%4-0.5% to 2%4-0.3%, and the tensile strength of the coatings increased from 564-4 MPa up to 734-3 MPa. In addition, the corrosion resistance of the coatings was also deeply influenced by process gas temperature. The corrosion kinetics of the coatings were affected by both of the plastic deformation of deposited particles and the porosity in the coatings.
基金supported by National Natural Science Foundation of China(No.52005133)Self-Planned Task of State Key Laboratory of Robotics and System(HIT),China(No.SKLR202002C)+1 种基金the Fundamental Research Funds for the Central Universities,China(No.AUGA5710050320)the Science Challenge Project,China(No.TZ 2016006-050301)。
文摘Cold spray is an attractive and rapidly developing process for additive manufacturing with high efficiency and precision,repairing and coating,especially in aircraft and aerospace applications.Cold spray additive manufacturing deposits micro-particles with large plastic deformation below their melting point,eliminating heat effect zone which could deteriorate the quality of repairing zone.The particle deposition in cold spray is a complex process which involves high strain rate,high contact pressure and high temperature.Here we develop,utilize and validate a thermomechanical model to provide a definitive way to predict deposition mechanics and surface deformation evolution for particle deposition process in cold spray additive manufacturing.Both a single particle and dual particles models were developed to investigate the contact interaction between particle/substrate and particle/particle.Different combinations of particle/substrate materials(Cu/Cu,Al/Al,steel/steel,and nickel/nickel)and process parameters were considered in this study.The experimental study was conducted to validate simulation results,providing useful information for understanding the limitations and challenges associated with cold spray additive manufacturing.The framework provides insights into improving the quality and precision of stress/strain formation,particle interactions and particle deposition in cold spray additive manufacturing process.
基金supported by Korea Institute for Advancement of Technology(KIAT)grant funded by the Korea Government(MOTIE)(P0002007,The Competency Development Program for Industry Specialist)。
文摘Cold spray(CS)which has recently become a promising additive manufacturing(AM)technology,was used to fabricate ultra-strong pure copper.In addition,the effects of carrier gas species on the microstructural characteristics,mechanical properties and deformation mechanisms were systemically explored.The CSAM copper manufactured with N_(2) carrier gas reveals a heterogeneous bimodal microstructure consisting of ultra-fine grains at the particle interface and relatively coarse grains in inner particles.With He carrier gas,a homogeneous grain structure consisting of ultra-fine grains in most areas was obtained.Compressive tests showed that N_(2) and He carrier gasses enabled ultra-high yield strengths of 340 and415 MPa,respectively.These values are comparable to severely plastic deformed copper,which has extremely low ductility and shape fidelity.On the other hand,both samples showed a strain-softening phenomenon that does not commonly occur at room temperature.The deformation microstructures revealed that dynamic recovery(DRV)and dynamic recrystallization(DRX)phenomena were generated despite being deformed at room temperature.Based on the above findings,the overall deformation mechanisms according to the carrier gas species in the CSAM copper manufacturing process were discussed.Furthermore,the work hardening and softening behaviors of CSAM Cu are predicted by using a constitutive equation.
文摘In this study, an innovative approach was used to fabricate Ti–Ta composite biomaterials through cold spray additive manufacturing followed by a diff usion treatment. The microstructure and mechanical properties of the composites were investigated in detail using field emission scanning electron microscopy, electron backscatter diff raction, 3D X-ray computed tomography, tensile test, nanohardness test and resonance vibration test. The obtained results indicated that the prepared composites have inhomogeneity in their microstructure and composition. A unique microstructure, composed of Ti-rich, Ta-rich and diff usion regions, was evolved in the composites due to incomplete diff usion between Ti and Ta splats. Further, Kirkendall pores were formed in the composites due to uneven diff usion of the two phases(of Ti and Ta) during high-temperature heat treatment. The prepared composites simultaneously showed low elastic modulus and high tensile strength which is required for a good biomaterial. Low elastic modulus was associated with the residual pores and the alloying eff ect of Ta in Ti, while high tensile strength was related to the solid solution strengthening eff ects. The obtained results indicated that the prepared Ti–Ta composites have a great potential to become a new candidate for biomedical applications.
基金supported by the National Natural Science Foundation of China (Nos.50871019 and 50874009)
文摘Particles may rebound from a substrate surface during cold spraying, which affects the quality of the coating. In this paper, the rebound phenomenon and its consequences on deposition behavior have been analyzed using the finite element analysis software ANSYS/LS-DYNA version 970. In a range of particle velocities of 50-1000 m/s, increases of the impact velocity caused a rapid decline of the rebound coefficient R to a low point Rmin. After that, R began to rise slowly. Then the effect of the impact velocities and material properties on the rebound phenomenon were analyzed. Both the material strength and density influenced this rebound phenomenon. Four stages of the impact process and a model of strain distribution were proposed in detail to explain the rebound phenomenon.
基金supported by the National Natural Science Foundation of China(Nos.52405356,52061135101,52071265)Jiangxi Provincial Natural Science Foundation Project,China(No.20242BAB20200)the National Key Research and Development Program,China(No.2021YFB3200500).
文摘The particle acceleration behavior and deposition mechanism of cold spraying aluminum matrix composites(Al_(2)O_(3)/2024)are complicated by the addition of ceramic particles.The effects of different feeding rates and particle diameters on critical velocity and mechanical properties were studied by numerical simulation and experiment.The results indicate that as the powder feeding rate increases,the impact velocity of gas and particles gradually decreases,and the temperature of gas and particles increases,resulting in an increase in the difference between particle impact velocity and critical velocity.The highest tensile strength of the deposit is achieved at a powder feeding rate of 1 r/min,which is 343 MPa.As the powder feeding rate increases,the performance of the deposits decreases,but it significantly saves time and cost.As the particle diameter increases,the impact temperature first increases and then decreases,resulting in the critical velocity first decreasing and then increasing,and the mechanical performance first increasing and then decreasing.To some extent,the best performance of the deposit is achieved when the size of the metal particle is close to that of the ceramic particle.
基金financially supported by the National Natural Science Foundation of China (Nos.51671205 and 51801217)。
文摘Cold spray(CS) is considered as a new type of repairing technique for restoration or remanufacturing of a wide range of unserviceable engineering components due to its unique ‘cold’ characteristic. In this work, a viable repairing approach i.e. "cold spraying followed by hot rolling post-treatment" was successfully applied to restore defective neutron shielding B_(4)C/6061 Al composite plates. Scanning electron microscopy(SEM) and electron backscatter diffraction(EBSD) results revealed that the coating-substrate interface is in a good bonding state without micro-cracks. Hot rolling post-treatment resulted in improved microstructure of the as-sprayed deposit with more uniform distribution of B_(4)C particles in the matrix.Moreover, well bonded splat boundaries and strain free Al grains were evolved in the matrix due to enhanced splat deformation and continuous dynamic recrystallization(CDRX). Three-point bending test results revealed that the strength of the repaired material is at par with the in-service plates. The findings of this work could be considered as a great stride to further extend possible applications of CS for repairing engineering structural components.
基金National Nature Science Foundation of China(50871019 and 50874009)
文摘Cold spraying is a new coating process and manufacturing technology.The coating quality is upgraded with dense layers,higher bonding force and lower oxidation comparing with thermal spraying.Bonding of particles onto substrate is a result of extensive plastic deformation and related phenomena at the interface.The cold-sprayed copper and aluminum deposits on aluminum and steel substrates were prepared,and the features of interface were observed by using scanning electron microscope(SEM).Then the particle/substrate impact process was modeling through finite-element methods(ANSYS/LS-DYNA software).Numerical results show that the high plastic strain at the interface can result in an adiabatic shear instability at the interface.Due to these extremely high pressure and strain rate,it may be more appropriate to treat the material adjacent to the particle/substrate interface as a viscous‘fluid-like’material,various fluid-based phenomena,such as interfacial instabilities and roll-ups and vortices,can lead to interface material mixing.In numerical simulation,adiabatic shear instability both in the particle and the substrate at contact interface is regarded as a criterion for predicting the optimal process parameters and the bonding feature.
