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This study systematically investigates the flow behavior of 7050 aluminum (Al) alloy produced via spray forming and subjected to a proposed pretreatment through thermal compression tests. The experimental findings reveal that the peak stress increased with decreasing deformation temperature or increasing strain rates. The parameters in the Arrhenius constitutive model were determined and verified by experimental results for spray formed (SFed) 7050 Al alloy. Hot deformation activation energy of the SFed 7050 Al alloy (147.38 kJ/mol) is notably lower than that of cast Al–Zn–Mg–Cu–Zr alloys, which is attributed to factors such as fine grains, low segregation, pores, and dispersed Al3Zr induced by pretreatment. Furthermore, processing maps have been constructed at various strains, revealing optimal stable deformation conditions at 300–450 °C/0.001–0.15s−1 and 425–450 °C/0.2–1s−1. Microstructural analysis of deformed samples highlights the critical role of dynamic recrystallization in influencing the stable and unstable areas of the alloy, which may be activated by high temperature and slow strain rate. The hot deformation mechanism of the SFed Al alloy is governed by interactions among η-Mg(Zn,Al,Cu)2 precipitates, dispersed Al3Zr particles, dislocation structures, and (sub-)grain boundaries.

In order to obtain homogeneity and fine-scale microstructure of Cu–Fe alloy, a Cu-10 wt% Fe alloy slab was prepared by spray forming. The effects of cold rolling reduction on the alloy microstructure, mechanical properties, and electrical conductivity were studied. The results indicate that the Fe phase was fine and uniform with an average particle size of 4.16 μm, and the morphology of the particles was short rod or nearly spherical. The Cu matrix and Fe particles were gradually elongated, refined and finally formed into a distinct fiber structure along the rolling direction as the cold rolling reduction increased from 35 to 95%. The degree of deformation of the Cu matrix was more significant than that of the Fe phases at the same reduction, and more refined grains of the Cu matrix around the Fe phases. After cold rolling at 95% reduction, the Cu-10 wt% Fe exhibited an increase in tensile strength from 337 MPa in the initial state to 595 MPa, while the electrical conductivity decreased from 42.3% IACS to 20.2% IACS. The alloy deformation behavior and the strengthening mechanisms were illustrated. The combination of spray forming and cold rolling provides a novel approach to producing efficient, shortened process, environmentally friendly Cu–Fe alloy thin strips. A new process of preparing homogeneity and fine-scale microstructure Cu-10 wt% Fe alloy thin strip by spray forming and clod rolling is proposed. Fine and uniform Fe particles were obtained with an average size of 4.16 μm. Combined with the subsequent cold rolling, the effects of different reductions on the microstructure and mechanical properties after cold rolling were systematically studied. The specific abstract summary is as follows: [ABSTRACT FROM AUTHOR]

This research aimed to enhance the strength and ductility of spray formed (SFed) 7050 aluminum (Al) alloy through hot extrusion and subsequent heat treatment. Microstructure and mechanical properties evolution during these processes were investigated. It was found that the low densification of the SFed 7050 Al alloy due to various defects such as pores, with an average size of 7.6 μm and an area fraction of 3.7 % could be notably enhanced by hot extrusion, even achieving a level close to theoretical density. This process led to a transformation of grains from equiaxed to elongated shapes along extrusion direction and significant grain refinement, exhibiting a strong fiber texture. While the employed extrusion ratio exceeds 16 with proper heat treatment, the SFed 7050 Al alloys achieves superior strength-ductility combination compared with reported Al alloys. The achieved high performance should be attributed to the grain refinement, strong texture and high densification that suppress defect-induced plastic instability. Furthermore, the combination of hot extrusion and heat treatment, provides an effective way to enhance strength and ductility for SFed 7050 Al alloy.

Spray forming is a manufacturing process that enables the production of high-performance metallic materials with exceptional properties. Due to its rapid solidification nature, spray forming can produce materials that exhibit fine, uniform, and equiaxed microstructures, with low micro-segregation, high solubility, and excellent workability. Al-Zn-Mg-Cu alloys have been widely used in the aerospace field due to their excellent properties, i.e., high strength, low density, and outstanding machinability. The alloy manufactured by spray forming has a combination of better impact properties and higher specific strength, due to its higher cooling rate, higher solute concentration, and lower segregation. In this manuscript, the recent development of spray-formed Al-Zn-Mg-Cu alloys is briefly reviewed. The influence of hot working, i.e., hot extrusion, hot forging, and hot rolling, as well as different heat treatments on the property and microstructure of spray-formed Al-Zn-Mg-Cu alloys is introduced. The second phases and their influence on the microstructure and mechanical properties are summarized. Finally, the potential in high-temperature applications and future prospects of spray-formed aluminum alloys are discussed. [ABSTRACT FROM AUTHOR]

In the present study, the influence of the addition of copper (Cu) on the wear behavior of a Al-12.6Si eutectic alloy developed using the spray forming (SF) method was discussed, and the results were compared with those of as-cast (AC) alloys. The microstructural features of the alloys were examined using both optical and the scanning electron microscopy, and the chemical composition and phase identification were achieved by X-ray diffraction (XRD) analysis. The results revealed that the microstructure of binary the SF alloy consisted of fine primary and eutectic Si phases, evenly distributed in the equiaxed α-Al matrix, whereas the Cu-based SF ternary alloy consisted of uniformly distributed fine eutectic Si particulates and spherical-shaped θ-Al2Cu precipitates, uniformly distributed in α-Al matrix. In contrast, the AC ternary (Al-12.6Si-2Cu) alloy consisted of unevenly dispersed eutectic Si needles and the coarse intermetallic compound θ-Al2Cu in the α-Al matrix. The addition of Cu enhanced the micro hardness of the SF ternary alloy by 8, 34, and 41% compared to that of the SF binary, AC ternary, and binary alloys, respectively. The wear test was conducted using a pin-on-disc wear testing machine at different loads (10–40 N) and sliding velocities (1–3 ms−1). The wear tests revealed that SF alloys exhibited an improved wear behavior in the entire applied load and sliding velocity range in comparison to that of the AC alloys. At a load of 40 N and a sliding velocity of 1 ms−1, the wear rate of the SF2 alloy is 62, 47, and 23% lower than that of the AC1, AC2, and SF1 alloys, respectively. Similarly, at a sliding velocity of 3 ms−1, the wear rate of the SF2 alloy is 52%, 42%, and 21% lower than that of the AC1, AC2, and SF1 alloys, respectively. The low wear rate in the SF2 alloy was due to the microstructural modification during spray forming, the precipitation of fine Al2Cu intermetallic compounds, and increased solid solubility. The SF alloys show an increased transition from oxidative to abrasive wear, while the AC alloys demonstrate wear mechanisms that change from oxidative to abrasive, including delamination, with an increase in sliding velocity and load. [ABSTRACT FROM AUTHOR]

This article addresses the tribological characteristics and the influence of mechanical work on the porosity of spray formed Al–Si–Pb alloys. Al‐alloys are extensively utilized in industry due to their self‐lubricant qualities, particularly in the bearing company. In the case of immiscible alloys, the spray approach is the most convenient way to adopt since it allows for single‐step fabrication. The spray process has a high cooling rate, which affects the microstructure of alloys and results in equiaxed grain morphology. Spray deposition and several factors affecting to it are discussed here. This study examines the effect of secondary processes such as cold rolling, hot rolling, extrusion, and so on on porosity, hardness, tensile strength, and tribological behavior. A comprehensive knowledge of the principles of spray techniques and their respective influence on tribological properties are discussed in this perspective by comparing the available literatures, and a future scope for better development is emphasized. [ABSTRACT FROM AUTHOR]

Ferritic stainless steels armored with borides had their endurance tested in demanding both abrasive and corrosive environment. The degradation was investigated through a very aggressive plate-on-cylinder wear test in water-based drilling mud containing chlorides, which was designed to simulate, in laboratorial scale, the corrosive tribosystem found in the wear of risers and casings used in deep water oil exploitation. A commercially-grade 430 ferritic stainless steel containing boron content far beyond its solubility limity, namely 1.2 and 3.5 wt.%, was processed by spray-forming to induce a ferritic stainless steel matrix protected by a boride skeleton. Additional corrosion assessment was performed by potentiodynamic polarization and electrochemical impedance spectroscopy in 0.27 M KCl solution, since KCl is a common clay swelling inhibitor. For comparison, API 5L X80 steel was also included since this material is used in risers and casings manufacture. The addition of boron (1.2 and 3.5 wt.%) led to the formation of microstructures composed of an α-ferrite matrix with homogeneously distributed M2B-type borides of different morphologies. Electrochemical tests revealed high corrosion resistance of the alloy with 1.2 wt.% B. However, the alloy with 3.5 wt.% B showed a considerable decrease in corrosion resistance due to Cr-depletion of the ferritic matrix given the M2B formation richer in Cr. Therefore, the alloy with 1.2 wt.% B offered the best tribocorrosion resistance.

Spray forming is a manufacturing process that enables the production of high-performance metallic materials with exceptional properties. Due to its rapid solidification nature, spray forming can produce materials that exhibit fine, uniform, and equiaxed microstructures, with low micro-segregation, high solubility, and excellent workability. Al-Zn-Mg-Cu alloys have been widely used in the aerospace field due to their excellent properties, i.e., high strength, low density, and outstanding machinability. The alloy manufactured by spray forming has a combination of better impact properties and higher specific strength, due to its higher cooling rate, higher solute concentration, and lower segregation. In this manuscript, the recent development of spray-formed Al-Zn-Mg-Cu alloys is briefly reviewed. The influence of hot working, i.e., hot extrusion, hot forging, and hot rolling, as well as different heat treatments on the property and microstructure of spray-formed Al-Zn-Mg-Cu alloys is introduced. The second phases and their influence on the microstructure and mechanical properties are summarized. Finally, the potential in high-temperature applications and future prospects of spray-formed aluminum alloys are discussed.

Herein, 440C martensitic stainless steel (440C MSS) is manufactured by spray forming (SF) technology. Microstructural and mechanical properties such as strength, ductility, and toughness are evaluated after quenching and tempering–partitioning (Q–TP) and quenching–intercritical–quenching–tempering (Q–IQ–T) heat treatments. The microstructural features that control the deformation and fracture behavior of the heat‐treated specimens are discussed. The experimental results show that after austenitizing at 1050 °C, the material exhibits no apparent plastic deformation before fracture. However, specimens austenitized above 1050 °C and the specimen subjected to Q–IQ–T exhibit an improvement in the tensile properties by showing an elastic–plastic transition that is related to the strain‐induced martensitic transformation of retained austenite formed during the Q–TP process and to a decrease in the volume fraction of martensite with increasing austenitizing temperature. Also, it is observed that the strain hardening rate decreases with increasing austenitizing temperature. Furthermore, the stress–strain data suggest that the Q–IQ–T heat treatment effectively improves the toughness and ductility of the steel without compromising strength. The results indicate that the mechanical response of the SF‐440C MSS can be tailored by adjusting the heat treatment parameters to enable better design for industrial applications. [ABSTRACT FROM AUTHOR]

The mechanical properties and microstructure evolution of the spray formed 2195 alloy extruded sheet at warm forming temperatures (100 °C–300 °C) were systematically investigated in this work. The results showed that the yield strength and ultimate tensile strength of the alloy declined obviously as the temperature rose, while the elongation increased initially and then decreased. With an increase in the strain rate, the yield strength and elongation of the alloy decreased, whereas the tensile strength increased. In addition, the tensile fracture behavior of the alloy was significantly affected by the temperature, and the fracture mode gradually shifted from intergranular fracture to ductile fracture as the temperature rose. The softening mechanism of the alloy was dominated by the dynamic recovery at different temperatures, and a certain degree of dynamic recrystallization was observed at 300 °C, which resulted in a dramatic decrease in the dislocation density of the alloy. Moreover, with an increase in temperature, coarser grains also appeared. Besides, the dislocation density and grain size of the alloy decreased initially and then increased with an increasing strain rate. Finally, it was found that the texture component of the alloy under different test conditions was mainly composed of deformation textures such as Brass and S. With the temperature increasing, the alloy showed a decrease first and then an increase in the texture strength, while the texture strength of the alloy increased continuously as the strain rate increased.

In this study, fine position samples of heat affected zone under single and secondary thermal cycles were simulated by heat treatment method. The influence of secondary thermal cycle on softening behavior and mechanism of heat affected zone in TIG-welded spray formed 7055 aluminum alloy were studied. The results showed that the mechanical properties of the solid solution zone decreased after the second thermal cycle. The hardness of the solid solution zone decreased from 180HV to 103HV and the tensile strength decreased from 570 MPa to 346 MPa after the second thermal cycle. The main reasons for the reduction of mechanical properties in the solid solution zone after the second thermal cycle were the weakening of the solid solution strengthening effect and the occurrence of over-aging. After the second thermal cycle in the over-aging zone, the mechanical properties decreased and then increased with the increase of the thermal cycle temperature. The lowest hardness value in the over-aging zone after the second thermal cycle decreased from 124HV to 103HV, and the tensile strength decreased from 410 MPa to 284 MPa. The main reason for the decrease of mechanical properties in the overaging zone after the secondary thermal cycle was the intensification of overaging caused by the coarsening of η phase. Overall, the width of the heat affected zone increased after the secondary thermal cycle, and the most seriously softened area extended toward the fusion line.

The mild–severe wear transition of aluminum alloys is considered evidence that the wear changes from a stable state to an unstable state, which is of great importance in engineering applications. The purpose of this study is to evaluate the mild–severe wear transition of the 2195 Al–Li alloy for different loads and to elucidate the causes behind it. To this end, dry sliding tribometric tests were carried out by varying the normal load from 2 to 40 N at room temperature. The results show that the change in wear rate can be divided into three distinct stages, including weak growth at low load (2–4 N), rapidly increased growth at medium load (8–16 N), and gradually increased growth at high load (32–40 N). The transition from mild to severe wear is observed at loads ranging from 4 to 8 N. Characterization of the worn surface of the Al–Li alloy via scanning electron microscopy shows that abrasion and oxidation are the dominant wear phenomena in the mild wear regime. On the other hand, delamination, adhesion, and severe plastic deformation become dominant in the severe wear regime. The reason for the occurrence of the transition is the tribo-induced plastic deformation of the substrate. [ABSTRACT FROM AUTHOR]

In the present study, the influence of the addition of copper (Cu) on the wear behavior of a Al-12.6Si eutectic alloy developed using the spray forming (SF) method was discussed, and the results were compared with those of as-cast (AC) alloys. The microstructural features of the alloys were examined using both optical and the scanning electron microscopy, and the chemical composition and phase identification were achieved by X-ray diffraction (XRD) analysis. The results revealed that the microstructure of binary the SF alloy consisted of fine primary and eutectic Si phases, evenly distributed in the equiaxed α-Al matrix, whereas the Cu-based SF ternary alloy consisted of uniformly distributed fine eutectic Si particulates and spherical-shaped θ-Al2Cu precipitates, uniformly distributed in α-Al matrix. In contrast, the AC ternary (Al-12.6Si-2Cu) alloy consisted of unevenly dispersed eutectic Si needles and the coarse intermetallic compound θ-Al2Cu in the α-Al matrix. The addition of Cu enhanced the micro hardness of the SF ternary alloy by 8, 34, and 41% compared to that of the SF binary, AC ternary, and binary alloys, respectively. The wear test was conducted using a pin-on-disc wear testing machine at different loads (10–40 N) and sliding velocities (1–3 ms−1). The wear tests revealed that SF alloys exhibited an improved wear behavior in the entire applied load and sliding velocity range in comparison to that of the AC alloys. At a load of 40 N and a sliding velocity of 1 ms−1, the wear rate of the SF2 alloy is 62, 47, and 23% lower than that of the AC1, AC2, and SF1 alloys, respectively. Similarly, at a sliding velocity of 3 ms−1, the wear rate of the SF2 alloy is 52%, 42%, and 21% lower than that of the AC1, AC2, and SF1 alloys, respectively. The low wear rate in the SF2 alloy was due to the microstructural modification during spray forming, the precipitation of fine Al2Cu intermetallic compounds, and increased solid solubility. The SF alloys show an increased transition from oxidative to abrasive wear, while the AC alloys demonstrate wear mechanisms that change from oxidative to abrasive, including delamination, with an increase in sliding velocity and load.

In recent years, rapid solidification techniques have garnered considerable attention due to their capacity to yield metals with unique microstructures and properties unattainable through conventional processing methods. These techniques involve swiftly cooling the metal, resulting in a fine-grained microstructure, unlike the coarse-grained microstructures typically obtained through traditional methods. This paper offers an overview of several rapid solidification techniques, such as melt spinning, spray forming, and gas atomization. These methods entail rapidly cooling molten metal by either quenching it onto a swiftly rotating wheel or spraying it onto a substrate. The cooling rates achieved, typically ranging from 104 to 107 K/s, far exceed those of conventional casting methods. The distinctive microstructure resulting from rapid solidification techniques presents numerous advantages over conventional methods. These include enhanced homogeneity, increased strength, improved ductility, heightened thermal stability, and augmented corrosion resistance. Consequently, rapid solidification techniques hold significant promise for applications across aerospace, automotive, and medical industries. This review also underscores recent advancements in rapid solidification techniques and their potential applications. These encompass the production of high-strength, wear-resistant materials for cutting tools, the development of lightweight alloys for aerospace applications, and the manufacture of biocompatible alloys for medical implants. In summation, this review offers a comprehensive examination of the latest progress in rapid solidification techniques for metal processing and their diverse applications across various industries.

In the present work, the microstructural studies of spray deposited Al‐6Si alloys with different lead content are conducted for 0% and 40% of rolling deformation. SEM and Optical micrographs are taken for different percentage of lead content. Fine equiaxed grain morphology is observed with a uniform distribution of Pb and Si phase in an Al‐matrix and it is found from the microstructures that the size of Pb particles increased with the increase in Pb content. Grains are stretched out in the rolling direction after cold rolling. Pore size is found to decrease after 40% rolling reduction, however, it is increased with the increase in Pb content. [ABSTRACT FROM AUTHOR]

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In this investigation, fine micro-zone specimens in the heat-affected zone (HAZ) of TIG welded spray formed 7055 aluminum alloy were obtained by heat treatment method. The softening behavior and mechanism of HAZ of this alloy under single pass TIG welding were investigated. Severe non-uniformities of microstructures and mechanical properties were found, according to which the HAZ was divided into the solid solution zone and the over-aging zone. The most heavily softened area of HAZ occurred in the over-aging zone at the position corresponding to the peak thermal cycling temperature of 230–350 °C. The lowest microstructures value was 105 HV, the lowest tensile strength was about 410 MPa. The elongation was slightly higher than that of the base material. The main causes of softening in the over-aging zone were the dissolution of the coherent precipitate η′ and the growth and coarsening of the non-coherent precipitate η.Thermal cycle temperature in the solid solution zone was about 350–536 °C. Mechanical properties in this zone were higher than those of the over-aging zone. After natural aging, mechanical properties recovered to more than 90% of the base material. Microhardness reached 180 HV and tensile strength reached 570 MPa when the thermal cycle temperature was 450 °C. At the same time, the elongation in the solid solution zone was higher than that of the base material. The high mechanical properties were the results of the combined action of the increased ratio of large angle grain boundaries, the increased solid solubility and the formation of coherent GPI zone.

In order to further enhance the strength and ductility of ultra-high strength aluminum alloys, the laser shock peening technology was applied to ultra-high strength Al-Zn-Mg-Cu alloy. The ultimate tensile strength, elongation and hardness can reach to 751 MPa, 11 % and 208.3 HV by combining spray forming, secondary extrusion, solid solution, retrogression and reaging as well as laser shock peening. The high strength and hardness of the alloys is mainly attributed to the fine-grained layer on surface as well as new grain boundaries, dislocation cells and high-density dislocations introduced by laser shock peening, uniform nano-sized strengthening phases with high density precipitated during heat treatments. The excellent ductility of the alloys is mainly ascribed to multiple structures including fine-grained layer on surface and slip lines inside different grains introduced by laser shock peening, smaller size of fibrous grains and Al 7 Cu 2 Fe phase produced by secondary extrusion and spray forming. The aging treatment after laser shock peening can lead to the annihilation of high-density dislocations as well as significantly promote the formation of stable and coarse η phase, which can greatly reduce the strength of the studied alloys. • The hardness and tensile property of Al-Zn-Mg-Cu alloys were improved by laser shock peening. • The performance improvement and microstructure modification mechanisms were revealed. • Combining spray forming, RRA and laser shock peening can obtain the optimum strength and plasticity. [ABSTRACT FROM AUTHOR]

Al-6Si-18Pb alloy was fabricated using spray deposition method with 430-mm flight distance followed by warm rolling. The microstructural change was studied using Optical Microscopy (OM), Field Emission Scanning Electron Microscopy (FESEM) and Electron Backscatter Diffraction (EBSD). Consequently, porosity, hardness properties and tensile behaviour followed by fractography was investigated. The results showcased a higher rolling deformation and continuous and discontinuous dynamic recrystallisation observed in the sprayed Al-6Si-18Pb alloy. The results also elucidated an increase in the rolling percentage from 0% to 60% along with refinement in the grain from coarse to fine structure. Further, the Pb atoms were homogeneously distributed in the Al matrix. The elongation and tensile strength for 60% warm-rolled sample at elevated temperature were 23% and 140 MPa, respectively, and the tensile fracture was lower at elevated temperature for warm-rolled samples. The porosity and hardness got significantly effected after warm rolling in comparison with the spray deposited specimen. [ABSTRACT FROM AUTHOR]

Antifriction alloys such as AlSn20Cu are key material options for sliding bearings used in machinery. Uniform distribution and a near-equiaxed granularity tin phase are generally considered to be ideal characteristics of an AlSn20Cu antifriction alloy, although these properties vary by fabrication method. In this study, to analyze the variation of the microstructure with the fabrication method, AlSn20Cu alloys are prepared by three methods: semi-continuous casting, semi-solid die casting, and spray forming. Bearing blanks are subsequently prepared from the fabricated alloys using different processes. Morphological information, such as the total area ratio and average particle diameter of the tin phase, are quantitatively characterized. For the tin phase of the AlSn20Cu alloy, the deformation and annealing involved in semi-continuous casting leads to a prolate particle shape. The average particle diameter of the tin phase is 12.6 µm, and the overall distribution state is related to the deformation direction. The tin phase of AlSn20Cu alloys prepared by semi-solid die casting presents both nearly spherical and strip shapes, with an average particle diameter of 9.6 µm. The tin phase of AlSn20Cu alloys prepared by spray forming and blocking hot extrusion presents a nearly equilateral shape, with an average particle diameter of 6.2 µm. These results indicate that, of the three preparation methods analyzed in this study, semi-solid die casting provides the shortest process flow time, whereas a finer and more uniform tin-phase structure may be obtained using the spray-forming process. The semi-solid die casting method presents the greatest potential for industrial application, and this method therefore presents a promising possibility for further optimization. [ABSTRACT FROM AUTHOR]

The study aims to investigate the microstructural and mechanical properties of Al-12.5%Si matrix composites reinforced with ZrO2 were fabricated by spray forming method and stir casting (SC) technique by varying reinforcement of 2%, 6% and 10 wt.% ZrO2 powder (size 25 μm).The spray-formed (SD) composites were subjected to hot (400°C) isostatic pressing to reduce the porosity. The microstructure of spray-formed and SC composites were examined using optical and SEM/ EDS. The microstructure of the spray-formed composites showed uniform distribution of fine Si, eutectic phase and ZrO2 particles in the equiaxed Al-matrix. In contrast, SC composites consist of a coarse Si, needle like eutectic phase and clustering of reinforcement particles at grain junctions as a continuous network along the grain boundaries. The hardness, ultimate tensile strength of both spray-formed and SC composites improved as the ZrO2 content increased, while yield strength decreased. Spray-formed composites showed better mechanical properties. This was attributed to uniform distribution fine of Si particles, reinforced particles, equiaxed matrix induced during spray deposition process. Tensile fracture surface of spray-formed composites possess ductile and cleavage fractures. SC composites showed intragranular cracks in coarse Si particles and increase in micro-cracks with increasing reinforcement. [ABSTRACT FROM AUTHOR]

Al–Si–Pb alloys are considered immiscible, and their synthesis is performed by spray forming. In this work the mechanical properties of Al–Si–Pb alloys were examined by varying Pb weight fraction (x = 0, 10, 15, and 20 wt.%). SEM and EDX analyses showed coarse and spherical lead particles in the microstructure due to the high melting temperature. Furthemore, with different melting temperatures of Si and Pb, the latter surrounded the Si particles. The wettability between Si and Pb was also quite high. Different phases and zones were analyzed using XRD micrographs. The alloy with 15 wt.% of Pb (Al–Si–15Pb) exhibited better mechanical properties. The SEM images demonstrated the microstructure of well-pushed lead particles within Al intertrial gaps. The primary purpose of the presented research is to optimize the torque and thrust forces during the drilling of the alloy, exhibiting the most reliable mechanical properties among Al–16Si–xPb (x = 0, 10, 15, 20 wt.%) alloys. The drilling operation on this alloy is based on factorial design experiments done following the response surface methodology (RSM) and binary-based model (BBM). The operated multi-objective particle swarm optimization (PSO) was applied to obtain the best combination of such drilling parameters as spindle speed, feed rate, and tool diameter based on the thrust force and torque responses. The integration of RSM and PSO allowed for predicting optimized responses. Eventually, the optimized results were applied experimentally and correlated with relative error. [ABSTRACT FROM AUTHOR]

This paper presents the study of the microstructure, wear properties of spray-deposited and hot compressed Al-35Si and Al-45Si alloys. The microstructure analysis and wear mechanisms of spray formed and as cast alloys were studied by using optical and scanning electron microscope (SEM). The microstructure of the spray-formed alloys showed fine particulate of primary Si and eutectic phases distributed uniformly in the equiaxed Al- matrix. Microstructural refinement was further increased in the hot-compressed alloys. Hardness, dry friction and wear tests were performed on spray formed alloys and compared with as cast alloys. Friction coefficient (COF) and wear rate of the alloys were measured under different applied loads (10–50 N) and sliding velocities of 1 and 1.5 m/s at constant sliding distance of 5000 m. The results indicated that the hardness and wear resistance of spray formed and hot-pressed alloys were considerably high over that of the as cast alloys. The improvements in hardness and wear resistance of spray-formed alloys were mainly attributed to morphology, size and distribution of Si particles induced during spray deposition process. Analysis of worn surfaces by SEM showed dominant wear mechanism of spray-formed alloy was mainly abrasive wear and oxidation wear. [ABSTRACT FROM AUTHOR]

The mild–severe wear transition of aluminum alloys is considered evidence that the wear changes from a stable state to an unstable state, which is of great importance in engineering applications. The purpose of this study is to evaluate the mild–severe wear transition of the 2195 Al–Li alloy for different loads and to elucidate the causes behind it. To this end, dry sliding tribometric tests were carried out by varying the normal load from 2 to 40 N at room temperature. The results show that the change in wear rate can be divided into three distinct stages, including weak growth at low load (2–4 N), rapidly increased growth at medium load (8–16 N), and gradually increased growth at high load (32–40 N). The transition from mild to severe wear is observed at loads ranging from 4 to 8 N. Characterization of the worn surface of the Al–Li alloy via scanning electron microscopy shows that abrasion and oxidation are the dominant wear phenomena in the mild wear regime. On the other hand, delamination, adhesion, and severe plastic deformation become dominant in the severe wear regime. The reason for the occurrence of the transition is the tribo-induced plastic deformation of the substrate.

Gleeble physical simulation technique was employed to investigate the high-temperature flow stress characteristics of the studied spray forming 7055 aluminum alloy. Simultaneously, the Arrhenius constitutive model which couples the parameter of true strain and the BP artificial neural network constitutive model were contrastingly utilized to predict the flow stress behavior of the experimental alloy. The result shows that the flow stress of spray forming 7075 aluminum alloy is significantly affected by deformation parameter, which is negative correlated with deformation temperature and positively correlated with strain rate. Through the comparison of the two models, the average relative error of the Arrhenius constitutive model lies over 2%. And the error of the model tends to increase with the rising temperature. Moreover, the average absolute error and the average relative error reach the maximum at hot processing temperature (around 450 ℃). It is difficult to precisely predict the flow stress characteristics of the alloy. However, BP artificial neural network constitutive model has higher prediction accuracy, the average relative error δ value is only 0.813% and has higher temperature stability.

The research and development in liquid metal atomisation and forming technologies of high performance metallic materials with the emphases on gas atomised superalloy powders, spray formed superalloys, powder metallurgy TiAl alloys and spray formed high-speed steels at Beijing Institute of Aeronautical Materials are reviewed. The technology and equipment of argon atomisation and minus atmospheric pressure atomisation (i.e. atomisation in sub-atmospheric pressure atomising assembly) of superalloy powders were established. Major factors contributing to powder oxygen content, particle size and non-metallic inclusions have been identified. A variety of high-purity, fine-grained and high-quality spherical powders of superalloys were produced , which have been utilised in the research and production of hot section components, such as turbine disks in advanced aero-engines. Spray forming technologies of highly-alloyed materials were investigated and developed while taking the key technical issues for making sound performs into process consideration, such as formation and deposition of droplets, densification and shape control, and hot working of preforms. The relative densities of as-deposited performs of superalloys and high-speed steels could be higher than 99.0% after the optimisation of process parameters. Low cost and high performance spray formed superalloys and high-speed steels were developed. Spherical powders of TiAl alloys with high purity and low oxygen content were obtained using the argon atomization techniques, and high performance sheets were subsequently deformed.

In this research, the effects of solid solution, peak aging (PA), over aging (OA) and retrogression re-aging (RRA) on microstructure, mechanical properties, and corrosion resistance of the spray-formed Al–Zn–Mg–Cu alloy were systematically and comparatively studied. It was found that after solid solution, most of the secondary phases dissolved into the α(Al) matrix and created a favorable condition for aging treatment. When the material was subjected to the RRA, the microstructure of the alloy consisted of fine precipitates within the grains similar to the PA condition and discontinuous coarse precipitates along the grain boundaries resembling the OA condition, allowing the RRA specimens to possess optimal strength (747 MPa) and high intergranular corrosion (IGC) resistance. The mechanism of IGC on mechanical properties on different aged samples was elaborated.

The research on hot deformation including flow behavior, microstructure evolution via EBSD method and the constitutive characteristic model of hot extruded GH738 alloy fabricated by spray forming was conducted by using Gleeble-3500TM simulator at the temperature range of 950~1150 ℃, strain rate range of 0.001~1 s–1 and engineering strain of 50%. The results show that the flow stress decreases with increasing of the deformation temperature and decreasing of the strain rate. The peak flow stress of coarse grain GH738 is higher than that of fine grain within the extruded GH738 alloy. The activation energy Q of extruded GH738 alloy is 651.08 kJ·mol–1. The hot deformation activation energy Q of GH738 alloy is tending to increasing with the decreasing of the original average grain size. The microstructure evolutes from original stretched grain to equiaxed grain with the increasing deformation temperature through the onset of recrystallization. The full dynamic recrystallization microstructure is obtained at the temperature above 1000 ℃ and the microstructure tend to coarsen with the higher deformation temperature.

In the present study, the microstructure and tribological performance of Al alloy has been enhanced by cryorolling. The Al-6 wt.% Si alloy has been selected as Al alloy which has been prepared by spray forming technique with 400 mm flight distance. Developed spray formed Al alloy has been subjected to cryorolling with different thickness reduction (25% and 50%) on non-reversing rolling mill using liquid nitrogen. The alteration in microstructure and tribological properties has been studied by different techniques. The microstructure results indicate that the cryorolling process refines the size of aluminium rich phase and silicon particles of spray formed Al alloy. The tribological testing results illustrate that the wear rate of Al alloy decrease by cryorolling. While the cumulative volume loss and wear rate increase with an increasing sliding distance and applied load for spray formed and cryorolled Al alloy. The coefficient of friction exhibits a fluctuating action with sliding distance while it decreases with an applied load and cryorolling. The worn surfaces have also been analyzed under scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and atomic force microscopy (AFM) techniques to study the operative wear mechanisms. Hardness property and microscopic analysis of Al alloy have also been correlated with tribological properties. [ABSTRACT FROM AUTHOR]

Antifriction alloys such as AlSn20Cu are key material options for sliding bearings used in machinery. Uniform distribution and a near-equiaxed granularity tin phase are generally considered to be ideal characteristics of an AlSn20Cu antifriction alloy, although these properties vary by fabrication method. In this study, to analyze the variation of the microstructure with the fabrication method, AlSn20Cu alloys are prepared by three methods: semi-continuous casting, semi-solid die casting, and spray forming. Bearing blanks are subsequently prepared from the fabricated alloys using different processes. Morphological information, such as the total area ratio and average particle diameter of the tin phase, are quantitatively characterized. For the tin phase of the AlSn20Cu alloy, the deformation and annealing involved in semi-continuous casting leads to a prolate particle shape. The average particle diameter of the tin phase is 12.6 µm, and the overall distribution state is related to the deformation direction. The tin phase of AlSn20Cu alloys prepared by semi-solid die casting presents both nearly spherical and strip shapes, with an average particle diameter of 9.6 µm. The tin phase of AlSn20Cu alloys prepared by spray forming and blocking hot extrusion presents a nearly equilateral shape, with an average particle diameter of 6.2 µm. These results indicate that, of the three preparation methods analyzed in this study, semi-solid die casting provides the shortest process flow time, whereas a finer and more uniform tin-phase structure may be obtained using the spray-forming process. The semi-solid die casting method presents the greatest potential for industrial application, and this method therefore presents a promising possibility for further optimization.

Monodisperse ZrO2 ceramic beads with size larger than 1 mm have been prepared by an improved micro‐droplet spray forming process, through which a compressor and a dispenser were employed to produce droplets continuously. Furthermore, the slurry recipe and drying temperature have been optimized to enhance the sphericity and smoothness of the beads. The sintered ZrO2 ceramic beads present promising mechanical performance, including a relative density of 84.6%, a crush strength of 256.2 ± 36.6 N as well as a Vickers hardness of 1344.4 ± 58.3 HV. Such procedure reveals great potential in mass production of ceramic beads. [ABSTRACT FROM AUTHOR]

In the present study, the microstructural characteristics, compressive strength, and corrosion behavior of aluminum-cenosphere composite foam (CF) developed by spray forming route (processed with 5 Psi (3.45 × 104 N/m2) and 10 Psi (6.90 × 104 N/m2) hydrogen pressure) has been undertaken. The microstructure of the spray-formed coupon consists of hollow cenosphere particles distributed uniformly in aluminum matrix. Compressive yield strength (YS) of the aluminum-cenosphere foam (CF) is different from commercially pure aluminum (cp-Al). It is found that the YS of the foam processed with 5 Psi is 83.62 MPa and for the foam processed at 10 Psi is 113.32 MPa as compared to 104.42 MPa for cp-Al. A detailed study of corrosion behavior through electrochemical measurements indicates that CF exhibits a reduced corrosion rate from 0.092 (for cp-Al) to 0.056 mm/year and 0.080 mm/year for the samples processed with 10 and 5 Psi, respectively. Through a detailed analysis of Nyquist and Bode plots derived from EIS measurements, it is concluded that mostly localized corrosion occurs in all the samples. The post-corrosion microstructural study confirms that interface of aluminum and cenosphere is the potential area for initiation of corrosion. [ABSTRACT FROM AUTHOR]

In this study, Al–6Si alloys with various Pb content (0, 10, 20, and 30 wt.%) were prepared by the spray deposition technique. Gaussian or bell-shaped spray deposits were obtained for different Al–6Si–xPb alloys at a pressure of 10 bar, at a nozzle to substrate distance of 450 mm, delivery tube with a diameter of 4 mm with a substrate inclination angle of 0°. Spray deposited Al–6Si–xPb alloys with variable Pb content were subjected to different rolling deformation. For the hardness measurements, samples were cut from the central and peripheral regions of the deposit containing different percentages of lead content. This paper examines the effect of deformation degree during different rolling reductions and the lead content of the spray deposited aluminum-silicon alloy on hardness behavior through the linear regression technique. A factorial design analysis was conducted to study the effect of different parameters, such as percentage of rolling deformation, variation of the lead composition, and preform distance from center to the periphery of the spray deposit. The influence of different rolling deformation on hardness values was more pronounced relative to that of the distance from the center to the peripheral region of the aluminum-silicon spray deposit with lead content. The hardness largely depends on the rolling deformation degree. Hardness values of the deposits were noted to increase with a higher deformation degree of the deposit, but it decreased as the Pb content increased. [ABSTRACT FROM AUTHOR]

The large-sized (?300 mm) nickel based superalloy GH738 billet was fabricated by spray forming followed by hot isostatic press (HIP) and hot extrusion (HEX) within varied deformation temperatures. The micro-defect, carbonitride distribution, γ/γ′ evolution during the hot processes were investigated by the relevant approaches including XRD, SEM, TEM, EBSD and phase analysis technique respectively. The results show that the porosities in γ matrix of spray deposited billet are welded up to closure after HIP process. The difference of characteristic microstructure after dynamic recrystallization obtained after the hot extrusion is mainly based on the varied deformation conditions including temperature and strain-stress state. The grain-boundary-distributed carbonitrides in HIPed billiet are transformed into extrusion-direction-along distribution after hot extrusion. The effects of temperature field delivered and cooling condition on elements constitution, mass fraction, morphology, size and distribution of γ′ in GH738 are validated during different hot processes as well.

Aluminum alloys fabricated by spray forming (SF) technology are commonly followed by hot-working without heat treatments. A new approach that is a pretreatment before hot-working is proposed in the present work. The results show that the microstructural stability of materials processed by this new approach is improved evidently, which is related to the pinning effect on dislocations and grain boundaries by Al3Zr particles induced during pretreatment. The strength of SF Al alloy processed by this treatment can be enhanced significantly. Owing to the combined effect of grain refinement strengthening, dislocation strengthening and precipitation strengthening, the yield strength and ultimate tensile strength can be enhanced by 171 MPa and 143 MPa, respectively. Based on experimental characterizations and a physical-based model, the underlying mechanisms regarding on enhancement of mechanical properties is mainly related to the induced Al3Zr particles and the optimized precipitates by the pretreatment.

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Double disks controller was used to constrain the size of spray plume. The flow field characteristics of the constrained spray technology under different gas inlet pressures were simulated by the computational fluid dynamics (CFD) software "Fluent", and the simulation result was experimentally verified. The results show that with the increase of atomization gas inlet pressure, the speed of reverse gas flow increases, and thus, the temperature of the nozzle tip decreases. In this case, solidification of the melt in the nozzle occurs. When the inlet pressures of the gas and metal are 2.5×105Pa and 2.0×104Pa respectively, the pressure acting on the melt decreases to minimum value of about 8.99×103Pa.At this condition, the molten metal flows out smoothly and no apparent oxidation phenomena appear in the deposition billet. Moreover, the effect of atomization is the best and the width of the deposition billet is exactly consistent with the width of the wheel groove of continuous extrusion machine.

Copyright of Journal of Aeronautical Materials is the property of Editorial Board of Journal of Aeronautical Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Recently it was shown that the Al–Cu–Fe–Cr system can form a microstructure consisting mainly of quasicrystalline and α-Al phases by arc-melting and subsequent annealing of an appropriate composition. In the present work we demonstrate that it is possible to fabricate a large volume of this composite directly from the liquid phase by spray forming an Al 85 Cu 6 Fe 3 Cr 6 (%at) alloy. The overspray powder and an arc-melted sample were also analyzed. Tribological properties of the Al-based composite reinforced with quasicrystals was evaluated by pin-on-disk tests, which demonstrated to be superior than an Al–Si alloy, A380, used in this work as a comparison material. Image, graphical abstract [ABSTRACT FROM AUTHOR]