Showing papers on "Spray forming published in 1999"

Thixoforming of a novel layered metal matrix composite

Abstract: Thixoforming is a semisolid processing route capable of producing near net shape components with low levels of porosity in a single, rapid operation. It has potential for the processing of aluminium alloy based metal matrix composites (MMCs). In contrast with casting of fully liquid metal, the flow of material into the die in thixoforming is primarily laminar. Thus, a novel layered MMC structure, generated by spray forming, consisting of alternate lamellae of reinforced and unreinforced alloy, might be preserved in thixoforming. The laminated structure is intended to give an increase in toughness, compared to a homogeneously reinforced material. The material was produced by spray forming alternate layers of aluminium matrix alloy 2014 (Al–4Cu–0·8Si–0·8Mn–0·5Mg) and matrix alloy reinforced with ∼17 vol.%SiC particles. Following thixoforming, the layered structure was well preserved with good retention of layer integrity and arrangement. Impact measurements for estimating toughness (Charpy and Izod...

The effect of spray forming on the microstructure and properties of a high chromium white cast iron

Abstract: The effect of spray forming on the structure and properties of a 17% Cr, 2.5% C white cast iron is described and compared with conventionally cast material of the same composition. Spray forming resulted in a substantial reduction in microstructural scale (eutectic (Cr,Fe)7C3 fields of up to 500 μm in conventionally cast material were replaced by discrete carbides of typically 2–8 μm diameter in the spray cast deposit). Carbide size varied as a function of position in the spray deposit, being approximately twice the size at mid section compared with either surface or interface with the collector. Carbide size was not altered by the gas to metal ratio used to atomise the spray. Spray forming increased transverse rupture stress and work of fracture by ∼50% compared with the conventionally cast material. Forging of the spray formed material was possible at ∼950°C, without inducing carbide fracture or void formation in the matrix. Quenching into iced water from 300°C induced extensive macroscopic cracking in the conventionally cast material whereas 400°C was required in the spray cast material to induce similar damage. The relationship between processing, microstructure and mechanical properties is discussed.

Modelling of billet shapes in spray forming using a scanning atomizer

Abstract: A numerical method is presented to predict and analyze the shape of a growing billet produced from the ‘spray forming’ which is a fairly new near-net shape manufacturing process It is important to understand the mechanism of billet growth because one can obtain a billet with the desired final shape without secondary operations by accurate control of the process, and it can also serve as a base for heat transfer and deformation analyses The shape of a growing billet is determined by the flow rate of the alloy melt, the mode of nozzle scanning which is due to cam profile, the initial position of the spray nozzle, scanning angle, and the withdrawal speed of the substrate In the present study, a theoretical model was first established to predict the shape of the billet and next the effects of the most dominant processing conditions, such as withdrawal speed of the substrate and the cam profile, on the shape of the growing billet were studied Process conditions were obtained to produce a billet with uniform diameter and flat top surface, and an ASP30 high speed steel billet was manufactured using the same process conditions established from the simulation

Method for plastically working aluminum alloy and high- strength/high-ductility aluminum alloy worked by the same

Abstract: PROBLEM TO BE SOLVED: To provide a plastically working method for an aluminum alloy which has excellent strength at a high temperature and ductility at the normal temperature and to which necessary plastic working is applied as keeping the state of a large sized preform and a high-strength/high-ductility aluminum alloy worked by the same method. SOLUTION: By the spray forming method by which the molten metal of the aluminum alloy is sprayed by an inert gas and accumulated while rapidly solidifying, the preform 3 is manufactured and, by equal cross-sectional area aside extruding method by which its extruding direction is changed at the midway to the side direction of an interior angle of <180 deg. without changing the cross-sectional area which is possessed by the preform by pressurizing the preform 3, shear deformation is imparted to the preform 3. It is preferable to take the strain e (e=2/√3 × cotan(ϕ/2), (ϕ: a conversion angle at the midway of the extruding direction of the preform)) of the shear deformation to be imparted as within the range of 0.5-2.5.

Chapter 7 Spray-forming

Abstract: Publisher Summary This chapter discusses the principle and variations of spray-forming. Spray forming is also termed as spray atomization and deposition in the academic field as well as the industrial community. The spray deposition stage involves the collection of droplets in the spray cone onto a water-cooled substrate, forming a dense bulk material that is normally referred to as a deposit. Spray forming is normally carried out in an environmental chamber. The chamber is evacuated and back-filled, with a protective gas, such as N2, He, and Ar. The products of spray-forming include the bulk deposit and powders that are usually termed as oversprayed powders. In close-coupled spray-forming, the molten metal is released from the crucible through a delivery tube. In free-fall spray-forming, the molten metal is released from the bottom of the crucible, forming a stream. The molten metal stream travels downwards, through the atomizer unit, until it is atomized at a certain point below the atomizer. In reactive spray-forming, the atomization gas reacts with the droplets, forming inorganic phases, such as oxides, carbides, or nitrides.

Distribution of lead in lead-containing aluminium alloys obtained by liquid phase co-spray forming technique

Abstract: Liquid phase co-spray forming (LPCSF) technique was employed to produce Al-Pb and Al-Si-Pb alloys to show that it is possible, using this technique, to distribute lead into very fine-sized particles in Al/Al alloy matrix at low melt temperatures. Microstructural studies were carried out to explore the mechanisms governing lead distribution in the matrix of the alloys during processing. Results showed that, regardless of the alloy compositions and experimental conditions, the microstructures of the preforms exhibited great similarity, i.e. less uniform distribution of Pb particles in the base region, and uniform distribution of fine Pb particles in the equiaxed region. During LPCSF process, the behaviour of Pb droplets was similar to that of ceramic particles, except that the shape and size of liquid Pb phase varied corresponding to local solidification condition.

Microstructural evolution during reactive spray forming of dispersion strengthened Cu alloy

Abstract: Dispersion strengthened Cu alloy was fabricated by injecting Cu-B alloy powders into the spray of Cu-Ti droplets. The microstructures of over-sprayed powders and spray deposited billet were observed by optical microscopy, scanning electron microscopy, and transmission electron microscopy. The over-sprayed powders were composed of not only Cu-B and Cu-Ti alloy powders but also small amounts of Cu-B alloy powders surrounded by Cu-Ti droplets. Fine dispersoids of TiB were observed in the Cu-B powders surrounded by Cu-Ti, indicating that very rapid reaction of Ti and B had occurred during the flight of the droplets. TiB dispersoids of ∼10 nm having an orientational relationship with the Cu matrix were distributed in the Cu-B alloy powder region and coarser TiB dispersoids of ∼50 nm were observed in the circumferencial Cu-Ti region. The spray deposited billet consisted of the regions showing a fine microstructure of round shape, presumably originating from the injected Cu-B alloy powders, and a relatively coarse cellular microstructure. TiB2 and TiB of ∼200 nm were observed along the grain and cell boundaries. Fine TiB dispersoids of ∼10 nm having an orientational relationship with the Cu matrix were observed in both regions. The solidification behavior, with special interest in (he formation of dispersoids, was examined based on this observation.

Thermal cracking in large diameter spray formed billets

Abstract: During the production of large diameter spray formed copper and alloy steel billets, hot cracks were observed at the head with residual melt present during crack initiation. Temperature simulations were carried out to investigate the hot cracking phenomenon in the spray forming process. A commercial finite element program was used for the calculations with boundary conditions and assumptions based on experimental results. The temperature history of the billet was calculated during and after spraying. It is shown that different spray parameters influence the radial thermal gradient, especially at the top of the billet; reduced heat input at the top of the billet decreases the thermal gradient. In the experiments hot cracks are reduced or avoided with a lower heat input.

Gefüge und mechanische Eigenschaften von sprühkompaktiertem Stahl: Einfluss einer thermomechanischen Behandlung

Abstract: As a comparatively new primary shaping process, spray forming opens the possibility to manufacture semifinished products with a fine grain structure without segregations. However the spray forming of unalloyed low carbon steels shows some effects that can be regarded as disadvantages. Depending on the line of the process a porous region at the billet border and a Widmannstatten microstructure in the core of the billet can be noticed. By a following hot deformation of the billet the porosity and the microstructure can be modified considerably. Based on previous results the effects of rolling temperature and initial porosity on microstructure anti mechanical properties are investigated. Therefore samples with defined initial porosity were rolled with a variation of the temperature and submitted to tensile testings. The results are compared with those of the as spray formed and conventional cast material.

Spray forming method of insert

Abstract: PROBLEM TO BE SOLVED: To provide a technique for producing a high-performance insert which is not only more cost-effective but is unlimited in terms of chemical properties or in terms of a capability to incorporate a ceramic material. SOLUTION: This method forms the sheet insert by thermal spraying of a bulk material. This method has (a) a stage of preparing a mandrel which is a mandrel having the external dimension not larger than the desired internal dimension of the desired insert and has a means for separating the bulk material sprayed from the mandrel, (b) a stage of forming a bulk composite material having a density of at least 99% by thermal spraying one or more kinds of iron or nickel alloy in the presence of a controlled atmosphere and (c) a stage of forming the discrete sheet insert shapes by cooling the bulk material, then removing such material from the mandrel and slicing the material described above for fitting into the final products.

MICROSTRUCTURE AND AGE HARDENING OF Cu-15Ni-8Sn ALLOY PREPARED BY SPRAY FORMING

Abstract: The microstructure and age hardening of spray deposited Cu-15Ni-8Sn alloy have been investigated by using hardness measurement, optical microscope, electron probe, X-ray difFraction and transmission electron microscope. The microstructure of as sprayed Cu-15Ni-8Sn alloy was compared with that of the same alloy obtained by the conventional ingot metallurgy. The result showed that spray deposited Cu-15Ni-8Sn alloy exhibited the equiaxial grain and refined and homogeneous distribution of composition. Phase precipitation in alloy during age hardening treatment were also studied. It was suggested that spinodal modulation decomposition and the formation of metastable γ-(Cux, Ni1-x)3Sn phase with the DO22 ordered structure were two main causes of age hardening in spray deposited Cu15Ni--8Sn alloy.

Spray Forming Aluminum - Final Report (Phase II)

Abstract: The U.S. Department of Energy - Office of Industrial Technology (DOE) has an objective to increase energy efficient and enhance competitiveness of American metals industries. To support this objective, ALCOA Inc. entered into a cooperative program to develop spray forming technology for aluminum. This Phase II of the DOE Spray Forming Program would translate bench scale spray forming technology into a cost effective world class process for commercialization. Developments under DOE Cooperative Agreement No. DE-FC07-94ID13238 occurred during two time periods due to budgetary constraints; April 1994 through September 1996 and October 1997 and December 1998. During these periods, ALCOA Inc developed a linear spray forming nozzle and specific support processes capable of scale-up for commercial production of aluminum sheet alloy products. Emphasis was given to alloys 3003 and 6111, both being commercially significant alloys used in the automotive industry. The report reviews research performed in the following areas: Nozzel Development, Fabrication, Deposition, Metal Characterization, Computer Simulation and Economics. With the formation of a Holding Company, all intellectual property developed in Phases I and II of the Project have been documented under separate cover for licensing to domestic producers.

Evaluation of porosity in spray deposited A2 tool steel

Abstract: The objective of the present study is to provide a numerical model to serve as a guide in the determination of optimum processing parameters for the spray forming of tool steels. Porosity is predicted using a heuristic model that incorporates the effect of the relative magnitudes of the fluid flow characteristic time and the solidification characteristic time on the porosity formation process, Two regimes, the 'fast flow' regime and the 'fast salidification regime, are identified a priori. Expressions for porosity as a function of the particle size distribution, the over-age solid fraction of the incident spray, and the solidification contraction are derived, based on these assumptions. The average solid fraction of the incident spray is estimated from the droplet size distribution and the solid fraction of a single droplet of a given size. The fatter is determined by cakulating the droplet dynamics and thermal history. The effects of process parameters (melt superheat, atomization pressure, deposition distance, and melt mass flow rate) on the level of porosity are investigated. By determining the conditions corresponding to a minimom in predicted porosity, optimum processing parameters can be assessed. As a result, processing maps are provided as a reference for achieving spray fermed tool steels with minimum parosity.

Manufacture of semi finished steel or nickelous system alloy

Abstract: PROBLEM TO BE SOLVED: To improve abrasion resistance property or mechanical properties by making it a semi finished item, wherein a nitrogen or a nitrogen contained gas is sprayed, after a given value of titanium is added to a steel which does not contain a titanium or a nickel system liquid alloy. SOLUTION: A billet is made by a spray forming of an alloy, wherein a titanium added volume is set to be 0.01-2.5 wt.%, preferably 0.1-1.0 wt.%, in a nitrogen gas atmosphere. Thus, a titanium nitride is formed, being dispersively precipitated as a fine precipitate, and a material character of the alloy is improved by restraining a growth of grain size, coarse graining at the time the billet is finally solidified and cooled. Specifically, after adding 1% Ti to a given liquid metal composition, for example, a molten alloy composed of C: 0.1%, Cr: 12%, Mo: 1.75%, Ni: 2.5%, V: 0.3%, the nitrogen gas is used as a double spraying device. A dropping which being partially solidified with the liquid is sprayed to a moving collector disc so as to make a billet in a range of diameter being 200-500 mm, and of 2 m length.

Spray forming a metal deposit onto a heated ceramic pattern

Abstract: A method of spray forming a weldable metal deposit; said method comprising: (a) providing a ceramic spray forming pattern (14); (b) heating the spray forming pattern (14) to a sustained temperature sufficient to prevent internal stress formation in carbon steel having a carbon content of less than about 0.3 weight percent deposited on the heated spray forming pattern; (c) spraying metallic particles (42) onto the spray forming pattern (14) heated to the sustained temperature, the metallic particles (42) having a carbon content which is sufficient to result in metal particles having a carbon content of less than about 0.3 weight percent when deposited on the heated spray forming pattern (14); and (d) allowing the sprayed metallic particles (42) to cool to form a metal deposit (44) having a carbon content of less than about 0.3 weight percent.

Aluminum or aluminum alloy sputtering target and method for manufacturing the same

Abstract: The sputtering target is manufactured by adjusting the ratio of the gas flow volume (Nm3)/molten liquid flow mass (kg) to 5 Nm3/kg or more in the gas atomizing step of the spray forming method using an Al or Al alloy sputtering target material in which the maximum length of all the inclusions is 20 mum or less.