Microstructures and properties of Al-45%Si alloy prepared by liquid-solid separation process and spray deposition

The microstructures and properties of A1-45%Si alloy prepared by liquid-solid separation （LSS） process and spray deposition （SD） were studied. The results show that the size, shape and distribution of the primary Si phase have different influence on the properties of alloys. Comparing with the Si particles with irregular shape, fine size and continuous distribution in SD alloy, the primary Si phase in LSS alloy is sphere-like, coarse and surrounded by the continuous AI matrix. The microstructure features of LSS alloy are beneficial to the higher thermal conductivity and lower thermal expansion coefficient at room temperature. The fine Si particle in SD alloy is advantageous to improving the mechanical properties. The increasing rates of thermal expansion coefficient with temperature are influenced by the distribution of the Si particles, where a lower rate is obtained in SD alloy with continuous Si particles. The agreement of thermal expansion coefficient with the model in LSS alloy differs from that in the SD alloy because of the different microstructure characteristics.

Age-hardening characteristic of an Al-Zn-Mg-Cu alloy produced by spray deposition

Al-10.8Zn-2.8Mg-1.9Cu alloy was synthesized by spray atomization and deposition technique. GP zones and age-hardening process in the alloy were investigated using high-resolution electron microscopy （HREM）, selected area diffraction （SAD）, and differential scanning calorimetry （DSC） analysis. The results indicated that spray deposition process accelerated the aging kinetics of the alloy at an aging temperature of 120℃, thereby reducing the peak aging time to 16 h. GPⅠ and GPⅡ are the two types of zones that are major precipitates for the alloy under peak-aged condition. The precipitation sequence for the alloy is also discussed.

Spray deposition of FeCrNiMn and high carbon steel coatings by thermite reaction

A novel surface cladding technique was developed to prepare the FeCrNiMn alloy and high carbon steel cladding layers,and the microhardness,bonding strength,abrasion wear and corrosion resistance were investigated.The microstructures of the cladding layers were analyzed by using X-ray diffraction(XRD),scanning electron microscopy(SEM),and energy dispersive spectrometry(EDS).The results show that the bonding strength between the substrate and the two cladding layers were(432.6±21)and(438.3±12)MPa,respectively.Vickers hardness values of the two cladding layers were HV418.5and HV329.6,respectively.The corrosion current densities of the two coatings were2.926×10–6and6.858×10–6A/cm2after electrochemical corrosion test in3.5%NaCl solution,and the wear rate were1.78×10–7and1.46×10–6mm3/mN after sliding wear test,respectively.This indicates that a well metallurgical bonding between the coating and the substrate was achieved,the abrasion wear and corrosion resistance of both coatings had been greatly improved compared with the substrate.The novel cladding technology is promising for preparing wear-and-corrosion resistant coatings.

In situ TiB2/Cu composites fabricated by spray deposition using solid-liquid and liquid-liquid reactions

In situ TiB2/Cu composites were fabricated by both solid-liquid(S-L)and liquid-liquid(L-L)reactive spray deposition in combination with cold rolling and annealing.The microstructure and properties of the fabricated TiB2/Cu composites were investigated.The results show that the reactive mode and rolling treatment are the main factors affecting the microstructure and properties of the TiB2/Cu composite.The in situ reaction in the L-L reaction can be carried out more completely.By controlling the rolling and annealing process,the relative density and the properties of the as-deposited composites are optimized.The comprehensive performance of the deformed TiB2/Cu composite prepared by L-L reactive spray deposition(401 MPa and 83.5%IACS)is better than that by S-L reactive spray deposition(520 MPa and 20.2%IACS).

CREEP PROPERTIES OF HIGH SILICON ALLOY ZA27 PREPARED BY SPRAY DEPOSITION

The elevated temperature creep properties(90-150℃) of high silicon(～6wt%Si) alloy ZA27 prepared by spray deposition have been investigated by means of ball hardness testing method.The results indicate that the creep properties of the material prepared by spray deposition are notably improved,compared to that of the conventional casting alloy ZA27.The creep activation energy of the spray deposited alloy ZA27 is 3.9-5.7 kJ/mol higher than that of the conventional casting alloy ZA27.The creep formulation in this experiment is also derived as follows:HB-2-HB0-2=K exp(- Q/3RT)(t1/3-t01/3)The reasons for the improvement of creep resistance are also discussed from a microstructural point of view.

Spray deposition for making large size billet with swing atomizer

The movement mode of the atomizer is a very important parameter during spray deposition process,which has direct influence on the size and surface texture of the billets. To resolve the problem of manufacturing large size billets,a method of spray deposition by the atomizer with off-center swing was put forward. The atomizer was driven by the alternating current servomotor to swing within 7° at varying speed. The influence of the atomizer parameters,such as translation of the atomizer,swing angle of the atomizer,substrate falling speed and spraying pressure,on the spray deposition was studied. The optimized parameters of the spray deposition process were obtained. The results show that the large size billets with uniform surface quality can be made through adjusting swing frequency and angle of the atomizer,offset distance of the atomizer and inclined angle of the substrate; the valid spray area will decrease and the dimension of top surface will reduce when pressure is less than 0.4 MPa within certain spray distance; meantime,the moving time and cooling time of the droplets are extended,which will lead to loose structure and bad densification. When the pressure,the swing angle and the eccentric offset of the atomization equal 0.5 MPa,7° and 60 mm,respectively,large size billets with fine texture and diameter of 500 mm can be produced.

Biodegradable Polylactide-co-glycolide (PLGA) Thin Films Prepared by Electrospray and Pressurized Spray Deposition

PLGA thin films were prepared onto implantable devices by the electrospray and pressurized spray method. Thin films with structural gradients were obtained by controlling four parameters consisting of solution concentration, applied voltage, air pressure , and deposition time. The surface morphologies of the deposited films were observed using scanning electron microscopy （SEM）. The image analysis revealed the control factors on the preparation of PLGA thin films. The beaded structure is ensily formed with a decrease in polymer concentration while the fibrous structure is easily formed with an increuse in polymer concentration. With the increase in applied voltage, the surface morphologies changed continnously from a small amount of fibrous shape to a large fibrous one： a small amount of.fibrous shape at 10 kV, more fibers with non-uniform diameter at 20 kV, and most fibers with uniform diameter at 30 kV. Low air pressure（0.1 MPa ） corresponded to round particles while high air pressure （0.3 MPa ） corresponded to fiat particles. The change in thickness from 5.34 to 10.1μm was a result of deposition time increasing from 5 to 10 s. From our above work, films of the bead or fiber structures can be obtained by changing electrical parameters to impropvc tbe biocompntibility of the film.

Preparation of 6066/SiC-p composites by multilayer spray deposition

SiC particulate reinforced 6066 aluminium alloy metal matrix composites (MMCs) were prepared by multi layer spray forming. The preparation technology and process parameters were discussed. It is shown that SiC particulate can be continuously and evenly fed and co deposited in the spray forming process. The reciprocally scanning movement of spraying system can make the SiC particulates distribute homogeneously in the composite. The ratio of SiC particulates captured by the metal matrix is influenced by process parameters, especially the metal flow rate. 6066/SiC p composite preforms of d 300 mm×540 mm and tubes with a size of up to d 650/ d 300 mm×1 000 mm were made by the same process. After extrusion and T6 heat treatment, the multi layer spray deposited 6066/SiC p composites can achieve improved properties. [

Effects of fan speed on spray deposition and drift for targeting air-assisted sprayer in pear orchard

In order to reduce the application dosage of pesticides,a targeting air-assisted(TAA)sprayer was developed and tested in this study.Fruit trees were assayed by an infrared detection system to determine if the canopy needs to be sprayed.This TAA sprayer was compared with conventional air-assisted(CAA)sprayers,and the impacts of various fan speeds(0,800 r/min,1300 r/min,and 1800 r/min)on spray deposition,coverage,and drift amount were tested.Ponceau 2R was used as tracer to measure spray deposition under each treatment.Droplet coverage and canopy deposition were best when the CAA application fan speed was increased to 1300 r/min,but at higher fan speeds,spray deposition and coverage in canopy did not increase because extra air flow blew droplets from the ground into the air.During TAA spraying,droplet sizes increased at opening and closing moments.Optimal spray effects were achieved when the auxiliary airflow velocity was increased at a fan speed of 1800 r/min.The research provides a useful reference for the design of TAA and parameters optimization method with respect to the relationship between droplets deposition into tree canopy,ground and drift in the air.

Solidification microstructures of Al-Zn-Mg-Cu alloys prepared by spraydeposition and conventional casting methods

High strength Al-Zn-Mg-Cu alloys were prepared by spray deposition and casting techniques. The microstructures of the Al-Zn-Mg-Cu alloys were studied using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Secondary phases in the microstructures of the alloys prepared by spray deposition and conventional cast were examined. The results indicate that under the conventional casting condition, the microstructure of the alloy revealed the presence of coarse Al/Mg（ZnCu）2 eutectic phases, and the spray deposited process causes an obvious modification in size, morphology, and distribution of secondary phases in the microstructure as well as reduction of segregation. The superior microstructure of the spray-deposited Al-Zn-Mg-Cu alloy was attributed to the high cooling rate, and associated with the rapid solidification process.

Spray Deposition Behavior and Numerical Simulation of Growth of Tubular Preform in Spray Forming Process

Analysis on the deposition behavior of spray on deposition surface was made and an optimization method for the movement parameters （u, ω） of substrate was obtained. Simultaneously, a mathematical model of growth of tubular preform, specifically aimed at the kind of atomizer that is fixed and with a tilt angle was established. By in- tegrating the optimization method and the mathematical model, the growth process and shape of preform were simu- lated. The results show that the tilt angle of atomizer plays an important role on the dimensions and shapes of tubular preforms and it can provide a guidance for the development of spray forming equipment.

MICROSTRUCTURE AND TENSILE PROPERTIES OF RAPIDLY SOLIDIFIED Al－3．8Li－0．8Mg－0．4Cu－0．13Zr ALLOY PREPARED BY SPRAY DEPOSITION

Al-3.8Li-0.8Mg-0.4Cu-0.13Zr alloy was prepared by a novel spray deposition technique,and its microstructure and tensile properties after various aging treatments have been investigated. The experimental results show that the alloy,under study has very fine equiaxed grains about 5-20μm in diameter and a relative density of(94±3)% on average.Grains in the as-extruded alloy are'brick-like'in morphology,and few oxide particles have been found al the grain boundaries.δ' particles with irregular shape and'δ'-β''coprecipitates appear in the aged alloy.The coarsening of δ'particles is fast,and the distance between the particles does not widen so obviously as that of IM(ingot-casting method) alloys with increasing aging time.The spray deposited Al-Li alloy.reaches the peak-aged condition in a short time(10 h al 190℃) when the best properties(σb=534 MPa, σ0.2=480 MPa.δ=10%) are obtained.Compared with RSPM(rapid solidification processing method)Al-Li alloy,the ductility of the tested alloy has been obviously.enhanced while a comparable tensile strength is maintained.

Wear mechanism for spray deposited Al-Si/SiC_p composites under dry sliding condition

Al-Si/15%SiCp(volume fraction) composites with different silicon contents were fabricated by spray deposition technique, and typical microstructures of these composites were studied by optical microscopy(OM). Dry sliding wear tests were carried out using a block-on-ring wear machine to investigate the effect of applied load range of 10-220 N on the wear and friction behavior of these composites sliding against SAE 52100 grade bearing steel. Scanning electron microscopy(SEM) and energy-dispersive X-ray microanalysis(EDAX) were utilized to examine the morphologies of the worn surfaces in order to observe the wear characteristics and investigate the wear mechanism. The results show that the wear behavior of these composites is dependent on the silicon content in the matrix alloy and the applied load. Al-Si/15%SiCp composites with higher silicon content exhibit better wear resistance in the applied load range. Under lower loads, the major wear mechanisms are oxidation wear and abrasive wear for all tested composites. Under higher loads, severe adhesive wear becomes the main wear mechanisms for Al-7Si/15%SiCp and Al-13Si/15%SiCp composites, while Al-20Si/15%SiCp presents a compound wear mechanism, consisting of oxidation, abrasive wear and adhesion wear.

Characterization of microstructure evolution and mechanical properties of the spray-deposited AZ31 magnesium alloy

The cylindrical billets of a Mg-3Al-1Zn （AZ31） alloy were synthesized by spray deposition processing. The microstructure evolution and mechanical properties of the alloy were investigated. The results reveal that the microstructure of the AZ31 alloy is refined significantly by spray deposition processing. A homogeneous and equiaxial-grain structure with an average grain size of 17 μm is obtained. Further grain refinement with an average grain size of 5 μm is attributed to dynamic recrystallization during extrusion processing. The great increase in the density of grain boundary nucleation sites by the finer initial grain sizes makes the dislocation pile-ups near subgrain boundaries being absorbed easily by the boundaries, resulting in an accelerated recrystallization process. The average tensile ultimate and yield strengths of the extruded rods are 321 MPa and 237 MPa, respectively, with an elongation of 15.2% at room temperature, which are remarkably higher than those of the conventional as-cast AZ31 alloy.

Microstructure and mechanical propertiesof spray-deposited Al-Si-Fe-Cu-Mg alloy containing Mn

Al-20Si-5Fe-3Cu-1Mg alloy was synthesized by the spray atomization and deposition technique. The microstructure and mechanical properties of the spray deposited hypereutectic Al-Si alloy were studied using optical microscopy, scanning electron microscopy, X-ray diffraction, TEM (Transmission Electron Microscope) and HREM (High-resolution Electron Microscope), DSC (Differential Scanning Calorimetry), microhardness measurement, and tensile tests. The effects of Mn on the microstructural evolution of the high-silicon aluminum alloy after extrusion and heat treatment have been examined. The results show that two kinds of phases, i. e. S (Al2CuMg) and σ(Al5Cu6,Mg2), precipitated from matrix and improved the tensile strength of the alloy efficiently at both the ambient and elevated temperatures (300℃). The tensile test results indicate that the spray-deposited Al-20Si-5Fe-3Cu-1Mg alloy has better strength than the powder metallurgy processed Al-20Si-3Cu-1Mg alloy at elevated temperature.

INFLUENCE OF EXTRUSION ON DAMPING CAPACITIES OF AS-SPRAY DEPOSITED HIGH SILICON ALLOY ZA27 MODIFIED BY CERIUM

The effects of cerium modification and extrusion on the resultant damping behavior and mechanical properties of the as-sprayed high silicon alloy ZA27 were investigated in an thort to develop a new functional material possessing high damping capacity and good mechanical properties. The damping capacity, as well as the rslative dynamic modulus, was tneasured at frequencies of 1 and 4 Hertz over the 30 to 200℃runge. At below 80℃ the as-sprayed materials appear to be approximately Asquency independent. Above 80℃, the,naterials becotne temperature sensitive, exhibiting the highest damping for the lowest hequency. The extruded, as-sprayed high silicon alloy ZA27 modified by cerium has the highest damping capacity and elongation values among them. The micro8tructure of the as-sprayed high silicon alloy ZA27 modified by 0. 5 wt% cerium was made up of fine lamellar eutectoid, porositg, a light dot-like phase and a polygonal silicon-rich phase. Finally, the opemtive damping tnechanisms were discussed in light of the data obtained hem characterization of microstructure and damping capacity. The high damping capacity was attributed primarily to phase interface thermoelastic damping between the lamellar phases with various substrvctures,except for the grain refinement.

Microstructure and Mechanical Properties of Spray Deposited Ni-based Superalloys

Three kinds of superalloys were prepared by spray deposited process. The analysis results of microstructures and mechanical properties indicate that the spray deposited preforms with higher integral densification and the oxygen content in each kind of superalloy was very low. The microstructures are consisted of fine grain without dendritic equi-axed. The spray deposited superalloys possessed good ductility. The forging experiment displays that even though the once deformation of spray deposited GH742 alloy more than 60%, the crack can not be found. Meanwhile, the mechanical properties of spray deposited superalloys are significantly increased.

Simultaneously spray-assisted assembling reversible superwetting coatings for oil-water separation

Here,superhydrophobic cuprous oxide(Cu2O)with hierarchical micro/nanosized structures was synthesized via sprayassisted layer by layer assembling.The asprepared superhydrophobic meshes with high contact angle(159.6°)and low sliding angle(1°)are covered with Cu_(2)O "coral reef"like micro/nanosized structures.Interestingly,the superhydrophobic mesh surfaces became superhydrophilic again due to the oxidization of Cu_(2)O to CuO by annealing at a higher temperature(300℃).And the superhydrophobic properties would be recovered by heating at 120℃.Furthermore,the superwetting meshes were applied to design a miniature device to separate light or heavy oil from the wateroil mixtures with excellent separation efficiency.These superwetting surfaces by simultaneously sprayassisted layer by layer assembling technique show the potential application in universal oilwater separation.

Superplasticity of Spray Deposited 5083 Al-Mg Alloy

The superplasticity of spray deposited and thermomechanical processed 5083Al-Mg alloy is investigated in this paper. The results show that spray deposited 5083 Al exhibits anequiaxed grain morphology with an average size of 15 m and porosity in the range of 0.1 vol. % to 5vol. % . Two distinct TMP procedures are employed to close porosity and refine grain size:extrusion plus rolling and direct rolling. The material processed using the former method exhibits arelatively high superplasticity with a maximum superplastic elongation of 465 % , whereas thatprocessed using the latter method exhibits a maximum superplastic elongation of 295 % . Materialsprocessed using extrusion plus rolling and direct rolling both exhibit similar stress-strainbehavior and strain rate sensitivity factors. The strain rate factors are in the 0.3 to 0.5 range.The difference in their superplastic elongation is possibly the result of differences in grain sizeand available cavity nucleation sites provided by closed gas pores.

Effect of Precipitating Phases on Tensile Strength and Microstructural Stability of a Spray-Deposited Al-Si-Fe-Mn-Cu-Mg Alloy

Spray deposition is a novel process which is used to manufacture rapidly solidified bulk and near-net-shape preforms. In this study, AI-20Si-5Fe-3Mn-3Cu-1Mg alloy was synthesized by spray deposition technique. The aging process of the alloy was investigated by differential scanning calorimetry (DSC) analysis and transmission electron microscopy (TEM). The results show that two kinds of phases, i.e. S(Al2CuMg) and σ(Al5Cu6Mg2), precipitate from matrix and improve the tensile strength of the alloy efficiently at both the ambient and elevated temperatures (300℃). In addition, the σ-Al5Cu6Mg2 is a relatively stable phase which improves microstructural stability of the alloy.