Showing papers on "Spray forming published in 2006"

The effect of a simple annealing heat treatment on the mechanical properties of cold-sprayed aluminum

Abstract: Cold spray, a new member of the thermal spray process family, can be used to prepare dense, thick metal coatings. It has tremendous potential as a spray-forming process. However, it is well known that significant cold work occurs during the cold spray deposition process. This cold work results in hard coatings but relatively brittle bulk deposits. This work investigates the mechanical properties of cold-sprayed aluminum and the effect of annealing on those properties. Cold spray coatings approximately 1 cm thick were prepared using three different feedstock powders: Valimet H-10: Valimet H-20: and Brodmann Flomaster. ASTM E8 tensile specimens were machined from these coatings and tested using standard tensile testing procedures. Each material was tested in two conditions: as-sprayed; and after a 300°C, 22h air anneal. The as-sprayed material showed high ultimate strength and low ductility, with <1% elongation. The annealed samples showed a reduction in ultimate strength but a dramatic increase in ductility, with up to 10% elongation. The annealed samples exhibited mechanical properties that were similar to those of wrought 1100 H14 aluminum. Microstructural examination and fractography clearly showed a change in fracture mechanism between the as-sprayed and annealed materials. These results indicate good potential for cold spray as a bulkforming process.

An Overview of the Microstructures Present in High-Speed Steel -Carbides Crystallography

Abstract: The aim of the work was to prepare an overview about the microstructures present in high-speed steel, focused on the crystallography of the carbides. High-speed steels are currently obtained by casting, powder metallurgy and more recently spray forming. High-speed steels have a high hardness resulting from a microstructure, which consists of a steel matrix (martensite and ferrite), in which embedded carbides of different crystal structure, chemical composition, morphology and size, exist. These carbides are commonly named MxC, where M represents one or more metallic atoms. These carbides can be identified by X-ray diffraction considering M as a unique metallic atom. In this work, it is discussed, in basis of the first principles of physics crystallography, the validation of this identification when it is considered that other atoms in the structure are substitutional. Further, it is discussed some requirements for data acquisition that allows the Rietveld refinement to be applied on carbide crystallography and phase amount determination.

Microstructure Evolution During Spray Rolling and Heat Treatment of 2124 Al

Abstract: Spray rolling is a strip casting technology that combines elements of spray forming and twin-roll casting. It consists of atomizing molten metal with a high velocity inert gas, quenching the resultant droplets in flight, and directing the spray between mill rolls. In-flight convection heat transfer from atomized droplets and conduction heat transfer at the rolls rapidly move an alloy’s latent heat. Hot deformation of the semi-solid material in the rolls results in fully consolidated, rapidly-solidified product. While similar in many ways to twin-roll casting, spray rolling is able to process a broader range of alloys and operates at a higher production rate. A laboratory-scale strip caster has been constructed at INL and used to evaluate the interplay of processing parameters and strip quality while producing strips up to 200 mm wide and 1.6 – 6.4 mm thick. Plans are underway to scale to 600 mm width and demonstrate steady-state operation. As-spray-rolled strip is characterized by a flat, uniformly thick profile with minimal porosity or segregation. This paper examines how processing parameters influence the microstructure transformations that take place during spray rolling and post-deposition heat treatment of 2124 Al.

Using friction stir processing to fabricate Mg based composites with nano fillers

Abstract: There have been numerous methods in fabricating particulate reinforced metallic matrix composites, including stir casting, squeeze casting, spray forming, powder metallurgy, and mechanical alloying. In this paper, one solid state processing technique, friction stir processing, is applied to incorporate 5-15 vol% nano-sized ceramic particles SiO2 into the AZ61 Mg alloy matrix to form bulk composites, using the characteristic rotating downward and circular material flow around the stir pin. The upper working FSP temperature is controlled to less than 400 o C in order to avoid chemical reaction. The fixed pin tool is 6 mm in diameter and 6 mm in length, with a shoulder diameter of 18 mm and a 3 o tilt angle. The advancing speed of the rotating pin is kept constant to be 45 mm/min, with rotational speed of the pin from 800 rpm (rotation per min), resulting in a strain rate around 10 1 s -1 . After one-pass FSP, the particle dispersion within the central cross-sectional area of the onion ring regions, measuring nearly 6 mm in diameter, was macroscopically uniform. However, the observed particle size is frequently 0.5-5 µm, much larger than the individual SiO2 size (~20 nm), suggesting the clustering of nano particles. The situation after two FSP passes, with an opposite FSP direction for the second pass, appear to be further improved. Electron microscopy characterizations reveal that the aggregating particles were seen to vary from 10 to 1000 nm in size. Some of the large particles, 1-5 µm in diameter, were identified to be the Mn bearing dispersoids (e.g. Al4Mn) by the SEM-EDS. The average grain sizes of the composites with 5-15 vol% SiO2 varied within 0.5-2 µm, and the composites double the hardness as compared with the as-received AZ61 cast billet.

Strengthening and toughness of AZ61 Mg with nano SiO2 particles

Abstract: The strengthening mechanisms and bending toughness of the AZ61 Mg based composites reinforced by nano SiO 2 particles are examined. The composites were prepared either by spray forming, ingot metallurgy, or powder metallurgy, followed by severe hot extrusion. The spray formed composites exhibit the best nano particle distribution and toughness, but the volume fraction of the nano particles that can be inserted is limited. The nano composites fabricated through the powder metallurgy method possess the highest strength due to the extra strengthening effect from the MgO phase. Strengthening analysis based on the Orowan strengthening mechanism can predict well the composite strength provided that the nano particles are in reasonably uniform dispersion. For composites containing higher nano particle volume fractions greater than 3%, the experimental strength data fall well below the theoretical predictions, suggesting poor dispersion of the reinforcement.

Discrete break-up modeling of melt sprays

Abstract: Modeling of melt atomization for the production of metal powders, or for spray forming, is the focus of this study. In this context, several types of atomizer are used for inert-gas atomization resulting in disintegration of the melt. Here the fragmentation of a cylindrical melt jet in a free-fall gas atomizer was investigated by means of a discrete break-up model. The model analyzed the interaction process of the gas and the melt, and described the primary and secondary break-up of the melt stream. In the model, each fragment and droplet has been individually tracked through the flow field. The melts investigated were tin, copper, and steel. Finally, the resulting droplet-size distribution, and solid fraction of the droplets in the spray, were derived. The results of the computation have been compared with experimental data.

Modeling the Heat Flow in Spray Formed Steel Shells for Tooling Applications

Abstract: This article concerns a metal spraying process for the manufacture of production tooling at reduced time and cost. Critical to the successful operation of this process is control of the sprayed steel shell temperature to eliminate thermal residual stresses and distortion. A computational model of the transient heat flow in steel shells during spray forming has been developed. The critical data for the distribution of convective heat-transfer coefficient distribution over the shell surface and average spray temperature has been obtained from experiments using embedded calorimeters and process monitoring respectively. Shell average temperature and temperature variance have been investigated using the model, and predictions compared well with experimental measurements obtained using infrared thermal imaging. The wire feed rate was identified as the most suitable control parameter for a closed loop control system to regulate shell surface temperature during manufacture.

Spray Formed Superalloys and Their Fabrication Technologies

Abstract: As a novel technology to directly produce preforms or semi-products of metal materials using rapid solidification technique,spray forming has been rapidly developed to process high-alloyed and hard-to-process superalloys in recent yearsThe status of the spray forming of high temperature structural materials was briefly reviewed,including the development of the unique spray forming plants,spray atomization-deposition process and their applicationsThe spray forming route for compositionally complex high-strength nickel-base superalloy disks was also compared with conventional ingot metallurgy and powder metallurgy both metallurgically and economicallySound preforms of wrought,powder metallurgy and cast superalloys could be achieved by optimising spray atomization and deposition variables using either nitrogen or argon as atomisation gasThe high-quality preforms exhibited highdensity,refined grains,homogenous microstructures,segregation-free macrostructure,low gas contents,improved workability and enhanced mechanical properties

Spray Rolling Aluminum Strip

Abstract: Spray forming is a competitive low-cost alternative to ingot metallurgy for manufacturing ferrous and non-ferrous alloy shapes. It produces materials with a reduced number of processing steps, while maintaining materials properties, with the possibility of near-net-shape manufacturing. However, there are several hurdles to large-scale commercial adoption of spray forming: 1) ensuring strip is consistently flat, 2) eliminating porosity, particularly at the deposit/substrate interface, and 3) improving material yield. Through this program, a new strip/sheet casting process, termed spray rolling, has been developed, which is an innovative manufacturing technique to produce aluminum net-shape products. Spray rolling combines the benefits of twin-roll casting and conventional spray forming, showing a promising potential to overcome the above hurdles associated with spray forming. Spray rolling requires less energy and generates less scrap than conventional processes and, consequently, enables the development of materials with lower environmental impacts in both processing and final products. Spray Rolling was developed as a collaborative project between the University of California-Davis, the Colorado School of Mines, the Idaho National Engineering and Environmental Laboratory, and an industry team. The following objectives of this project were achieved: (1) Demonstration of the feasibility of the spray rolling process at the bench-scale level and evaluationmore » of the materials properties of spray rolled aluminum strip alloys; and (2) Demonstration of 2X scalability of the process and documentation of technical hurdles to further scale up and initiate technology transfer to industry for eventual commercialization of the process.« less

A Spray Coating and Its Mechanical Properties of Al-Si-Zn Alloy Produced by the Spray Forming Process

Abstract: A 55 mass%Al-1.5 mass%Si-Zn system alloy with good corrosion resistance was sprayed on a plaster substrate. Then, the formation process and some properties of the sprayed coating were investigated. Using the interrupted quenching method, it was found that the sprayed coating structure was not only the layer structure but also a casting structure. Due to large solidification range, the solidification pattern was a mushy type with characteristic of Al-Si-Zn alloys. The maximum temperature and the shrinkage ratio of the sprayed coating decreased as the spray distance increased, due to the decreasing melt particle temperature. Tensile strength and the elongation of the sprayed coating decreased as the spray distance increased, due to an increase in the porosity ratio. In particular, a large amount of oxide was formed in the sprayed coating when air was used as the carrier gas. This oxide formation causes an increase in the shrinkage ratio. [doi:10.2320/matertrans.47.1853]

The corrosion behaviour of a hypereutectic Al-Si alloy obtained by spray forming in acid, neutral and alkaline solutions

Abstract: Al-Si hypereutectic alloys produced by spray forming represent an important technological development for application in the aeronautical and automotive industries. Due to some special properties these alloys find application as cylinder liners, mainly due to their high strength and wear resistance. Much research has been carried out to evaluate the mechanical properties of these alloys but the literature on their corrosion performance is still very scarce. In this study, the corrosion behaviour of a spray formed Al-Si-Cu hypereutectic alloy was investigated by electrochemical impedance spectroscopy (EIS) in acid (pH 3.3), neutral (pH 7) and alkaline (pH 11) solutions. Intense localized attack occurred in the acid electrolyte and the impedance decreased with time of immersion. In the neutral medium, the alloy was passivated but localized attack also occurred on weak areas of the passive film. In the alkaline medium, precipitation of corrosion products occurred during the first hours of immersion causing the increase of impedance but thickening of this layer led to cracks growth with time and, consequently, to the exposure of metallic substrate, resulting in the decrease in impedance for longer periods.

New Light-Weight Aluminium Alloys with High Mg2Si-Content by Spray Forming

Abstract: Aluminum alloys with high Mg2Si-content (>10 %) offer the possibility of a significant decrease in density and an increase in stiffness at the same time. But these alloys can hardly be produced in casting processes, due to an oxidation and a generation of pores by hydrogen solubility of the melt. Furthermore, the usual solidification rate is not sufficient for a fine microstructure morphology. A fine distribution of Mg2Si is possible by spray forming, where a coarsening of the particles can be avoided due to a higher solidification rate. Different aluminum alloys with high Mg2Si-content (>10 %) have successfully been produced by spray forming, extrusion and age hardening. Mg-excess as well as Si-excess has been investigated. An additional alloying with copper leads to a further increase in strength by the precipitation sequence of Al2Cu. The new light-weight aluminum alloys have been investigated regarding age hardening, physical and mechanical properties. Densities of 2.5-2.6 g/cm3 and Young´s modulus of approx. 80,000 MPa have been found. Microstructures were dense, homogeneous and of fine morphology. The yield strength of these alloys reached values of approx. 400 MPa after artificial aging, whereby only a slight decrease for the hot yield strength was observed up to a temperature of 200 °C. Applications of the new light-weight aluminum alloys can be expected where a reduced density together with a high hot yield strength would lead to a more compact design in high temperature environments, e.g. in combustion engines.

On the texture of spray formed gamma titanium aluminide

Abstract: Spray forming is an attractive processing route for titanium aluminides that combines advantages both of ingot and powder metallurgy. Spray formed deposits were produced using the electrode induction melting gas atomization technique. The texture of a spray formed Ti–48.9 at.% Al deposit in the as-sprayed state and after isothermal forging as well as after isothermal forging and a subsequent stress relief heat treatment was analysed by means of neutron diffraction. The spray formed deposit was found to have a very weak 〈1 1 1〉-fibre texture with a maximum pole density of 1.12 multiples of random distribution. After isothermal forging of cylinders to 77% reduction at an initial strain rate of 2 × 10 −3 s −1 at 1150 °C, a band of orientations from 〈1 0 1〉 to 〈1 0 0〉 with a maximum close to 〈3 0 2〉 was found. A Zener–Hollomon parameter of 12.6 is estimated, which indicates that during isothermal forging dynamic recrystallization is governed by nucleation of new grains. A subsequent stress relief treatment at 1030 °C for 2 h caused additional grain growth, after which the maximum pole density is increased from 3.3 to 3.8 times random.

Method for jet deposition formation to preparing lanthanum matrix massive amorphous alloy

Abstract: Disclosed is a method for jet deposition formation to preparing lanthanum matrix massive amorphous alloy, which comprises preparing lanthanum-based master alloy by employing a vacuum electric induction furnace, then obtaining big blocks of amorphous La86-yAl14(Cu,Ni)y(y = 16-29 atomuN) through spraying deposition forming process, wherein the processing parameters for the spray forming is disclosed in the specification. The receiving substrate material employs red copper or red copper with Al2O3.SiC amorphous coating sprayed on the surface.

AZ61 Mg with Nano SiO2 Particles Prepared by Spray Forming plus Extrusion

Abstract: The current study applies the inclusion of thermally stable ceramic nano powders into the light weight AZ61 Mg base alloys via spray forming plus extrusion The combination of spray forming and severe extrusion provides a new processing route for fabricating nano composites, with uniform distribution of the nano fillers Parallel tries using the PM route followed by the same severe extrusion can also yield sound composites but the dispersion of the nano SiO2 appears to be less uniform The processed composites are characterized in terms of microstructure examination, thermal analysis, phase identification, and mechanical testing

A method for manufacturing metal components and a metal component

Abstract: A method for manufacturing metal components (9) by spray forming comprises depositing by spray forming a first layer (8) of a first metal on a mould, and depositing by spray forming a second layer (10) of a second metal on the first layer, wherein the materials to be deposited and the process conditions of the deposition are selected to produce the microstructure of the first layer (8) being optimised for the final use of the first layer surface (7) defined by the mould (2) on which the first layer is deposited, and the microstructure of the second layer (10) differing from that of the first layer and being optimised for the further actions to be performed to the second layer.

Microstructure variation of spray formed 70Si30Al alloy during heating procedure

Abstract: A novel 70Si30Al alloy was prepared by spray forming process for electronic packaging material.Microstructure variation of as-deposited preforms during heating procedure was studied.The results show that the microstructure is fine and homogenous,the primary silicon phases distributing in the alloy evenly are fine and irregular,and most of the phases that disperse between the primary silicon phases are supersaturated α(Al) and Al-Si Pseudo-eutectic phases.When the alloy is held under 620℃ for 90min,the primary silicon phases do not increase obviously and have spheroidized phenomenon with temperature increasing.The supersaturated α(Al)phases do not change significantly during heating procedure.The Al-Si pseudo-eutectic phases remelt in the temperature range from 566℃ to 582℃,and the mass of remelting phases increase with temperature increasing and they conglomerate together.The range of hot deformation temperature of spray formed 70Si30Al alloy is from 560℃ to 590℃.

Combination of Spray Forming and Metal Powder Productions by the Internal Mixing Atomizer with a Substrate

Abstract: This paper describes the performance of an atomizer coupled with a substrate which produces metal powder and spray forming materials simultaneous in the spray chamber. Ultra fine metal powders are produced from this process. The melt is atomized by a twin-fluid atomizer with internal mixing mechanisms. The molten spray injected from the swirling chamber of the atomizer is then impinged upon the substrate to form the two phase impinging flow. The deposition rate of the molten spray on the substrate is controlled by the diameter of the substrate, the height of the substrate ring and the distance of the substrate from the outlet of the atomizer. This in turn determines the powder production rate of the spraying processes. Experimental results indicate that the deposition rate of the spray forming material decreases as the distance between the substrate and the atomizer increases. For example, the deposition rate decreases from 48% to 19% as the substrate is placed at a distance from 20cm to 40cm. On the other hand, the metal powder production rate and its particle size increases as the substrate is placed far away from the atomizer. The production of metal powder with mean particle size as low as 3μ m level has been achieved, a level which is not achievable by the conventional gas atomization processes.

Effect of additional elements on aging behavior of Al-Zn-Mg-Cu alloys by spray forming

Abstract: 水花的 microstracture 和老化行为形成了 Al-Zn-Mg-Cu 合金我们 reinvestigated 作为 alloying 增加的功能。扔 theas 的合金的谷物与增加 Zn 元素被精制，这被揭示，当 Ni 增加的功能是岩山时引出处于同样渗出的条件的谷物边界粒子和 eutectic。包含 Mgand Zn 的粒子被发现内容增加与 Zn 增加，当 Ni 的角色是然后减少两个时这些粒子的棕土和尺寸。在一致的热处理以后，在谷物边界的抽出物的部分融化了，谷物没显然长大。在热挤出以后，更稠密的 microstracturebecomes 并且当有第二个阶段，沿着渗出的方向安排在纵的节时，在剖面图有许多猛抛的阶段。在人工老化期间， Zn 内容的增长不在山峰坚硬上生产许多效果，除了加速的过多 oftening。然而，大约 0.13% Ni 的增加在变老的温度产生不仅改进山峰坚硬而且性质稳定性的改进。

A method for spray forming a metal component and a spray formed metal component

Abstract: A method for spray forming a metal component (11, 17, 21, 27) having an elongated open channel (10, 20, 22, 28) therein comprises firstly spray forming a layer (8, 19, 24) of the desired metal onto a deposition substrate (2), placing then an elongated spray blocking object (9, 18, 26, 29) on the already sprayed layer for forming the channel, and continuing then the spray forming process until the desired total thickness of the component is achieved. According to the present invention, the spray blocking object is a strip (18, 26, 29), the cross-sectional profile of the strip being fully open in the direction of an axis (a) in a cross-sectional plane of the strip, and the strip is placed on the already deposited layer (8, 19, 24) with said axis directed substantially parallel to the direction of the incident metal spray (6).