Showing papers on "Spray forming published in 2000"

Microstructure and properties of titanium boride dispersed Cu alloys fabricated by spray forming

Abstract: Dispersion strengthened Cu alloys have been manufactured by conventional spray forming and also by reactive spray forming, followed by hot extrusion of the spray deposited billets. In this work, we have systematically investigated the relationship between the microstructure and mechanical properties of the Cu alloys fabricated through two techniques by means of optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and tensile testing. The size of dispersed particles in the reactive spray formed alloy was much finer than that in the conventionally spray formed alloy. That was because the dominant chemical reaction between Ti and B had occurred in Cu–Ti–B alloy melt in conventional spray forming while it had occurred after deposition of droplets in reactive spray forming. The yield strength of the reactive spray formed alloy was greater than that of the conventional spray formed alloy in spite of a lower volume fraction of reinforced particles. To understand the mechanism responsible for this experimental observation, the yield strength of the two Cu alloys were analyzed using the dislocation pile-up model and Orowan mechanism, which were fairly consistent with the experimental results. Increase in yield strength of reactive spray formed alloy compared with that of conventional spray formed alloy was largely attributed to nanoscale TiB dispersoids. This indicates that refining the reinforced particle size to nanoscale is of special importance for the development of high strength Cu alloys since the yield strength predominantly depends on the size and volume fraction of the reinforcement. From this point of view, reactive spray forming can be considered as a new promising process to develop high strength Cu alloys.

Droplet splashing during arc spraying of steel and the effect on deposit microstructure

Abstract: The mechanism by which droplet deposition occurs is important when filling substrate features for the electric arc spray forming of steel tooling. Particle image velocimetry and high-speed video imaging techniques have been used to observe droplet deposition, particularly with regard to the behavior of droplets originating from splashing. Droplet splashing on deposition has been seen to be significant, and splash droplets form a large proportion of the overspray. The splash droplets are smaller and, when first created, move slower than the parent droplet. When spraying into deep features, the lateral and upward movement of splash droplets acts as a mechanism for deposit formation onto surfaces in shadow from the main spray. Microstructural study has shown that oxidation of the splash droplets before redeposition leads to a deposit with a high fraction of oxide. Simultaneous growth of deposit formed directly from the spray, and from splash droplets, results in a banded microstructure containing elongated macropores. A mechanism for such microstructural evolution is proposed.

Formulation of rod-forming models and their application in spray forming

Abstract: In rod spray forming, the preform changes its shape continually from that of a disc to a rod (transient-state rod growth) and then maintains its top surface profile once it has settled down (steady-state rod growth). The rod growth mechanism during spray forming was analyzed using rod-forming models. At a sufficiently high substrate rotation velocity, the calculated results based on the three-dimensional time-dependent model (3-D TDM) and the two-dimensional time-dependent model (2-D TDM) were observed to be identical. The calculated results of the rod’s top shape, obtained by the TDMs, were almost identical to those obtained by the two-dimensional time-independent model (2-D TIM), which means that there exists steady-state rod growth. The effects of spray-forming parameters, such as initial eccentric distance, substrate withdrawal velocity, and spray angle, on the shape-evolution behavior were analyzed in terms of the vertex growth velocity ( $$\overline {G_o^v } $$ ). The optimum spray-forming condition to minimize transient-state rod growth was also presented. Experimental verification was made to confirm the proposed forming models.

Microstructural features induced by spray forming of a ternary Pb-Sn-Sb alloy

Abstract: An alloy containing Pb-12% Sn-12% Sb with small addition of copper and arsenic was spray deposited employing two different atomization gas pressure and nozzle to substrate distances. The temperature of the spray-deposit was measured during deposition at a distance of 2 and 10 mm above the substrate-deposit interface. Thermal profile data indicated small variation in temperature with time during deposition stage whereas during post deposition stage an exponential decrease in temperature was recorded. Second phase particle size along the thickness of the deposit varied from 4 to 8 μm compared to 70 to 80 μm size of these particles in the as cast alloy. Maximum porosity occurred in the section of the deposit near the contact surface of the substrate and also in its peripheral regions. X-ray diffraction analysis exhibited the formation of additional Cu2Sb phase in the spray-deposit and CuSn and Cu3.3Sb phases in atomized powders compared to that of the as cast alloy. The microstructural evolution during spray deposition of this alloy is discussed.

Grain refinement and stabilization in spray-formed AISI 1020 steel

Abstract: An AISI 1020-grade mild steel, with a small amount of aluminum, was spray-formed by nitrogen gas-atomization and deposition. The spray-formed 1020 steel contained 0.05 mass% of nitrogen and 0.06 mass% of aluminum. Rolling the spray deposit at 1123 K for a thickness reduction of 70% and subsequent normalizing at low austenitic temperatures produced a fully dense steel having a refined ferrite grain size as small as 3 μm. This grain refinement resulted from the pinning of prior austenite grain boundaries by fine AlN particles which precipitated during the thermomechanical treatments. Room-temperature tensile properties (YS: 550 MPa, UTS: 630 MPa, elongation: 23%), exceeding those of conventional microalloyed high-strength low alloy steels, were achieved in the normalized state. The AlN-pinned fine-grained microstructure survived subsequent re-austenizing at temperatures as high as 1273 K. When tensile-tested in the austenite region at 1123 K, the microalloyed 1020 steel showed a large elongation exceeding 200%.

Aluminium precipitates in the primary silicon of as-sprayformed hypereutectic aluminium-silicon alloys

Abstract: Precipitates have been observed in the primary silicon of as-spray-formed hypereutectic aluminium-silicon alloys with and without various alloy additions. The precipitates have been investigated using transmission electron microscopy and high-resolution transmission electron microscopy. They are aluminium based and generally adopt a spheroidal morphology, with diameters in the range of approximately 5-10nm, unless located on a stacking fault or grain boundary. Spray forming is a rapid solidification process and precipitation occurs because of the low solid solubility of aluminium in silicon (maximum of 0.016 +/- 0.003at.% at 1190 C). The morphology of the precipitates suggests that they form from aluminium or aluminium-rich liquid. The orientation relationships of several precipitates in one of the primary silicon grains have been determined.

Spray forming of ultra-fine SiC particle reinforced 5182 Al-Mg

Abstract: This paper describes the spray forming of SiC particle reinforced Al metal matrix composites (MMCs) with particular emphasis on microstructure characterization of SiC particle distribution. A 5182 Al-Mg alloy was used as matrix material, and SiC particles with a mean diameter of 1.2 μm and 2.0 μm as reinforcement. The reinforcing particle distribution and microstructural characteristics of MMCs were analyzed in the current study using TEM, SEM and optical microscopy. The distribution of SiC particles in the as-spray deposited and hot-extruded conditions was characterized. SEM results indicate that the SiC particles are homogeneously distributed although some clustering was evident in the matrix. TEM and OM examinations show that most of SiC particles are present intergranularly in the Al matrix. EDS analysis indicated that Mg tends to segregate and form oxide phases in the vicinity of SiC particles and that there is no compositional variation of Mg across grain boundaries in the Al matrix.

An analytical simulation of solidification behavior within deposited preform during spray forming process

Abstract: Solidification within spray deposited preform is one of the key processing stages of spray forming, which has a substantial influence on the formation of the final microstructure of the preform. For the sake of optimizing the process and getting desired microstructure and properties of the preform, the solidification behavior should be fully understood. In this investigation, a concept of ‘virtual’ solidification layer was applied to establish an analytical model to simulate the solidification behavior within the preform during spray forming process, which will provide clearer physical pictures of the solidification behavior. According to the model developed, a simulation of the solidification behavior was performed for a typical Al–Cu alloy. The results show that both the processing parameters (such as deposition rate and temperature of spray cone at the point of impingement) and the thermophysical properties of the material are the important factors controlling the solidification behavior. Even for the same thermodynamic state of spray cone at the point of impingement, the top surface temperature of the preform will change conspicuously as variation of the processing parameters or thermophysical properties of the material takes place, which will cause the variation of microstructure and properties of the preform. Therefore, the principle of taking the thermodynamic state of spray cone at the point of impingement as the key factor controlling the spray deposition process should be modified adequately. A new parameter (the surface temperature of the preform) for the processing control of spray forming was proposed.

A metal matrix composite based on boron steel

Abstract: The present invention relates to a metal matrix composite based on boron steel containing at least 0.0010 % boron by weight, produced by spray forming, comprising ceramic particles with a hardness greater than 800 HV, method for producing such a metal matrix composite, and metal matrix composites produced by said method.

Modeling of Spray-Formed Materials: Geometrical Considerations

Abstract: In this article, a mathematical model is formulated to predict the evolution and final geometry of an axisymmetric billet (i.e., round) obtained using an off-axis spray arrangement. The model is formulated by calculating the shape change of a profile curve of a billet surface, based on an axisymmetric surface. On the basis of this model, a methodology to determine the “shadowing effect” coefficient is presented. The modeling results suggest that there are three distinct regions in a spray-formed billet: a base transition region, a uniform diameter region, and an upper transition region. The effects of several important processing parameters, such as the withdrawal velocity of substrate, maximum deposition rate, spray distribution coefficient, initial eccentric distance, and rotational velocity of substrate, on the shape factors (e.g., the diameter size of the uniform region and the geometry of the transition regions) are investigated. The mechanisms responsible for the formation of the three distinct regions are discussed. Finally, the model is then implemented and a methodology is formulated to establish optimal processing parameters during spray forming, paying particular attention to deposition efficiency.

Aluminum alloy made impeller and manufacture thereof

Abstract: PROBLEM TO BE SOLVED: To surely prevent reduction of yield of products caused by cracking generated at the time of an after process by performing preliminary forging work for improving ductility, on a cylindrical impeller raw material formed in such a way that rapidly cooled and solidified aluminum alloy formed by a spray forming method is extrusion-worked within a specified temperature. SOLUTION: An impeller 1 is attached to a rotor shaft 2, and is disposed in a casing 9. In this case, rapidly cooled and solidified aluminum alloy of Al-Fe as a material of the impeller 1 is manufactured by means of such a spray forming method that fused metal is sprayed by inert gas and is stuck simultaneously with rapidly cooled and solidified with cooling speed of 102 deg.C/sec or more. After its manufactured mold is hot-extrusion worked within a temperature of 200 to 600 deg.C, preliminary forging work is performed for improving ductility of a surface layer in both side surfaces of the extrusion raw material. After that, regular forging work acted to an inside of the extrusion raw material, and stamping work using a prescribed mold are performed.

Spray Forming of FeSi2 Thermoelectric Material by High-velocity Oxy-fuel Thermal Spraying

Abstract: Large sized n-and p-type FeSi2 thermoelectric devices were spray-formed by high-velocity oxy-fuel thermal spraying (HVOF) method. One is a plate 100mm square with the thickness of 6mm and another is a tube-type device which was formed on a stainless tube (25 mm in diameter, 500 mm long) with the thickness of 5 mm. Their microstructure and physical properties were compared to those of hot-pressed material. The bulk density of HVOF-formed FeSi2 was lower than that of hot-pressed materials due to higher amount of pore. For n-type FeSi2, Seebeck coefficient and thermal conductivity of HVOF-formed material were comparable to those of hot-pressed material. While electrical conductivities of both n-and p-type HVOF-FeSi2 were quite lower than that of hot-pressed n-type material, resulted in low performance as thermo electric device.

Spray-formed tooling for injection molding and die casting applications

Abstract: Rapid Solidification Process (RSP) Tooling{trademark} is a spray forming technology tailored for producing molds and dies. The approach combines rapid solidification processing and net-shape materials processing in a single step. The ability of the sprayed deposit to capture features of the tool pattern eliminates costly machining operations in conventional mold making and reduces turnaround time. Moreover, rapid solidification suppresses carbide precipitation and growth, allowing many ferritic tool steels to be artificially aged, an alternative to conventional heat treatment that offers unique benefits. Material properties and microstructure transformation during heat treatment of spray-formed H13 tool steel are described.

Microstructure and internal friction of spray deposited Al-3.3Fe-10.7Si alloy

Abstract: Al-3.3Fe-10.7Si alloy has been experimentally made with spray deposition technology. The internal friction of the alloy which was directly associated with the microstructures under spray deposited, extruted and heat treated conditions has been investigated using a low frequency inverted torsion pendulum over the temperature region of 10–300 °C. An internal friction peak was observed in the temperature range 50–250 °C in the present alloy. The Q-1 peak decreased after extruted and in subsequent to the earliness of isothermal annealing, which was found to be directly attributed to the precipitation of FeAl2 and Al– Fe– Si intermetallics from the supersaturated aluminium alloy matrix. We suggest that the internal friction peak in the alloy originates from grain boundary relaxation, but the grain boundary relaxation can also be affected by FeAl2 and Al– Fe– Si intermetallics at the grain boundaries, which will impede grain boundary sliding.

Process for manufacturing AL-Si alloys for use in vehicle propeller shafts

Abstract: A process for manufacturing an Al—Si alloy for use in a vehicle propeller shaft is provided. The Al—Si alloy manufacturing process includes the steps of heating and melting Al—Si alloy where Si contains 13-40 weight percentage (wt %) of the whole alloy, to thereby prepare melt, maintaining the melt at 700-900° C. and then spraying an high pressure inert gas to the melt and rapidly solidifying the same to thereby obtain a forming body, and extruding the forming body at 400-550° C. The physical properties of the Al—Si alloy manufactured by a spray forming process is at least similar to that of the vehicle propeller shafts which have been already known, and also spotlighted as new alloy compositions which can replace the conventional propeller shaft material.

Application of a Novel Multilayer Spray Forming Technology in the Preparation of Large Dimension Aluminium Alloy Blanks

Abstract: 多层的水花由它形成和试管和营舍的准备技术的原则在文章被介绍并且描述。形成技术的多层的水花的显著特征是水花系统的往来活动的运动，因此预先形成是由有在形成进程的水花期间保留相对低的温度的存款的表面的层的扔的层。多层的水花形成的二个突出的优点如下：对生产大尺寸空白合适，更高的团结冷却率。现在 Al-Fe-V-Si 合金(8009 ) 并且原文如此，粒子增强了铝合金金属矩阵在直径和直到在外部直径，在内部直径的 360 公里和在长度的 1 200 公里的 650 公里的尺寸的管状的空白的 00 公里与技术被做了的 300 鈥 ? 的合成营舍。在挤出以后，材料有好性质。

Umformen und Sprühkompaktieren von Flachprodukten. Diskussion

Abstract: The production of flat products by spray forming, offers the possibility of the manufacturing of thin semi-finished material with optimized material properties. With the production of such thin slabs or sheet metals the small initial thickness reduces the range of following transforming handling steps. The occurring process-determined porosity, which appears negligible with large volume deposits, as well as problems with the production of a geometry suitable for the subsequent treatment, however obstruct the commercial use of the potentials of the spray forming process for other products, e. g. in sheet metals. The production process and studies for the workability of the flat products are the subject of this paper.

Production of iron-nickel base blank for shadow mask

Abstract: PROBLEM TO BE SOLVED: To provide a method for producing an Fe-Ni base blank for a shadow mask excellent in suppressing the occurrence of ununiform streaks after etching and working in a good yield. SOLUTION: This blank is produced by adopting a spray forming method consisting substantially of a process for vacuum-melting an Fe-Ni base base material at a temp, exceeding a liquids line temp., a process for gas-atomizing the resultant molten metal with gaseous N2 and a process for depositing the atomized molten drop in a half-solidified state. The temp, of the molten metal at the time of the gas atomization is preferably in the range from (the liquidus line temp, +50 deg.C) to (the liquidus line temp, +200 deg.C) or the ratio of the flow rate (m3/min) of gaseous N2 at the time of the gas atomization to the flow rate (kg/min) of the molten metal is preferably in the range of 0.3-3.0 (m3/kg).

Application of a novel multilayer spray forming technology in the preparation of large dimension aluminium alloy blanks

Abstract: Principle of multilayer spray forming and preparation technique of tubes and billets by it were presented and described in the article The marked characteristic of multilayer spray forming technology is the to-and-fro movement of spray system, so the preform is deposited layer by layer with the surface of the deposit retaining relatively low temperature during the spray forming process The two outstanding advantages of multilayer spray forming are as follows: suitable for manufacturing large dimension blanks, higher solidification cooling rate Now Al-Fe-V-Si alloy (8009) and SiC particle reinforced aluminium alloy metal matrix composite billets of 300–600 mm in diameter and tubular blanks of size up to 650 mm in outer diameter, 360 mm in inner diameter and 1 200 mm in length have been made with the technology After extrusion, the material has good properties