Medium-Frequency Electrical Resistance Sintering of Highly Oxidized Iron Powder

Highly oxidized iron powders were consolidated by means of the medium-frequency electrical resistance sintering technique (MF-ERS). In order to activate the powders and to disperse the oxides coating the particles, prior to the consolidation process, powders were milled in a high-energy mill for 7 minutes. Structural and mechanical characterisations of electrically consolidated compacts were carried out in order to study the effect of two main processing parameters (current intensity and heating time). The compact properties resulted to be very sensitive to these parameters, especially to the current intensity. A change from 5 kA to 10 kA in the current intensity makes the porosity to fall from 30% to 8%. Moreover, using a higher current intensity (10 kA) increases the mechanical properties of the final compacts: micro-hardness change in almost 50 HV, up to 104 HV 1, and compression resistance by around 500 MPa, up to 569 MPa.

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Production of Ultrafine Grained Hardmetals by Electrical Resistance Sintering

Metals ◽

10.3390/met9020159 ◽

2019 ◽

Vol 9 (2) ◽

pp. 159 ◽

Cited By ~ 4

Author(s):

Jesús Cintas ◽

Raquel Astacio ◽

Francisco Cuevas ◽

Juan Montes ◽

Thomas Weissgaerber ◽

...

Keyword(s):

Grain Size ◽

Grain Growth ◽

Electrical Resistance ◽

Processing Parameters ◽

Medium Frequency ◽

Main Achievement ◽

Processing Times ◽

Ultrafine Grained ◽

Protective Atmospheres ◽

Optimal Values

In this work, powders of cemented ultrafine WC-6 wt.% Co were consolidated. The feasibility of the medium frequency electrical resistance sintering (MF-ERS) technique were studied to prevent WC grain growth during consolidation. Porosity and hardness were measured at different zones of the MF-ERS compacts. The compacts showed a slight inhomogeneity in their properties across their section, but it was controlled by choosing suitable values of the processing parameters. The optimal values for the material studied were current intensities between 7 and 8 kA and sintering times between 600 and 800 ms. The main achievement using this consolidation method was that sintered compacts essentially maintained the initial WC grain size. This was attained to processing times of less than 2 s, and without the need for using protective atmospheres.

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Nickel Porous Compacts Obtained by Medium-Frequency Electrical Resistance Sintering

Materials ◽

10.3390/ma13092131 ◽

2020 ◽

Vol 13 (9) ◽

pp. 2131

Author(s):

Fátima Ternero ◽

Eduardo S. Caballero ◽

Raquel Astacio ◽

Jesús Cintas ◽

Juan M. Montes

Keyword(s):

Electrical Resistance ◽

Nickel Powder ◽

Low Voltage ◽

Applied Pressure ◽

Electrical Current ◽

Heating Time ◽

Medium Frequency ◽

Microhardness Distribution ◽

Furnace Sintering ◽

Porous Compacts

A commercially pure (c.p.) nickel powder was consolidated by Medium-Frequency Electrical Resistance Sintering (MF-ERS). In this consolidation technique, a pressure and the heat released by a high-intensity and low-voltage electrical current are concurrently applied to a metal powder mass. A nickel powder with a high tap porosity (86%) and a low applied pressure (only 100 MPa) is chosen in order to be able to obtain compacts with different levels of porosity, to facilitate the study of the porosity influence on the compact properties. The influence of current intensity and heating time on the global porosity values, the porosity and microhardness distribution, and the electrical conductivity of the sintered compacts is studied. The properties of the compacts consolidated by MF-ERS are compared with the results obtained by the conventional powder metallurgy route, consisting of cold pressing and furnace sintering. A universal equation to describe the porosity influence on all the analyzed properties of powder aggregates and sintered compacts is proposed and validated.

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Medium-Frequency Electrical Resistance Sintering and Electrical Discharge Consolidation of Metallic Powders

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.772.123 ◽

2018 ◽

Vol 772 ◽

pp. 123-127

Author(s):

Fatima Ternero ◽

Raquel Astacio ◽

Francisco Gomez Cuevas ◽

Jesus Cintas ◽

Juan Manuel Montes

Keyword(s):

Electrical Resistance ◽

Electrical Discharge ◽

Mechanical Characterization ◽

Processing Parameters ◽

Ultrafine Grain ◽

Medium Frequency ◽

Iron Powders ◽

Uniform Microstructure ◽

Sintering Time ◽

Ultrafine Grain Size

Compacts of iron powders were prepared by medium-frequency electrical resistance sintering (MF-ERS) and electrical discharge consolidation (EDC). Structural and mechanical characterization was carried out in order to study the effect of the main processing parameters (current intensity and sintering time in MF-ERS and voltage and capacity in EDC). The compact properties resulted to be quite sensitive to the consolidation method and parameters. Porosities around 8% and microhardness of about 120 HV were reached. It is concluded that the MF-ERS process can be a best option for the consolidation of cemented carbide composites with composition WC-6wt.%Co. MF-ERS compacts of this composite show a very low porosity and reasonable uniform microstructure, preserving the original ultrafine grain size and an adequate hardness with a very quick processing cycle of the order of one second.

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Influence of Processing Parameters on the Conduct of Electrical Resistance Sintering of Iron Powders

Metals ◽

10.3390/met10040540 ◽

2020 ◽

Vol 10 (4) ◽

pp. 540

Author(s):

Fátima Ternero ◽

Raquel Astacio ◽

Eduardo S. Caballero ◽

Francisco G. Cuevas ◽

Juan M. Montes

Keyword(s):

Electrical Resistance ◽

Low Voltage ◽

Applied Pressure ◽

Processing Parameters ◽

Heating Time ◽

Simultaneous Action ◽

Joule Effect ◽

Furnace Sintering ◽

Short Time ◽

Heat Released

The influence of the applied pressure and electrical parameters on the macrostructure of specimens consolidated by the medium-frequency electrical resistance sintering technique (MF-ERS) is analysed in this work. This technique is based on the application of pressure to a mass of conductive powder that, simultaneously, is being crossed by a high intensity and low voltage electric current. The simultaneous action of the pressure and the heat released by the Joule effect causes the densification and consolidation of the powder mass in a very short time. The effect of the current intensity and heating time on the global porosity, the porosity distribution, and the microhardness of sintered compacts is studied for two applied pressures (100 and 150 MPa). For the different experiments of electrical consolidation, a commercially available pure iron powder was chosen. For comparison purposes, the properties of the compacts consolidated by MF-ERS are compared with the results obtained by the conventional powder metallurgy route (cold pressing and furnace sintering). Results show that, as expected, higher current intensities and dwelling times, as well as higher pressures and the consolidation of compacts with lower aspects ratios, produce denser materials.

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Review: Filament Winding and Automated Fiber Placement with In Situ Consolidation for Fiber Reinforced Thermoplastic Polymer Composites

Polymers ◽

10.3390/polym13121951 ◽

2021 ◽

Vol 13 (12) ◽

pp. 1951

Author(s):

Yi Di Boon ◽

Sunil Chandrakant Joshi ◽

Somen Kumar Bhudolia

Keyword(s):

Processing Parameters ◽

Filament Winding ◽

Reference Points ◽

Thermoplastic Composites ◽

Manufacturing Processes ◽

Fiber Reinforced ◽

Consolidation Process ◽

Fiber Placement ◽

Automated Fiber Placement

Fiber reinforced thermoplastic composites are gaining popularity in many industries due to their short consolidation cycles, among other advantages over thermoset-based composites. Computer aided manufacturing processes, such as filament winding and automated fiber placement, have been used conventionally for thermoset-based composites. The automated processes can be adapted to include in situ consolidation for the fabrication of thermoplastic-based composites. In this paper, a detailed literature review on the factors affecting the in situ consolidation process is presented. The models used to study the various aspects of the in situ consolidation process are discussed. The processing parameters that gave good consolidation results in past studies are compiled and highlighted. The parameters can be used as reference points for future studies to further improve the automated manufacturing processes.

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Factors Affecting the Metal Recovery Yield during Induction Melting of Aluminium Swarf

Materials Science Forum ◽

10.4028/www.scientific.net/msf.730-732.781 ◽

2012 ◽

Vol 730-732 ◽

pp. 781-786

Author(s):

Hélder Puga ◽

Joaquim Barbosa ◽

Carlos Silva Ribeiro

Keyword(s):

Processing Parameters ◽

High Energy ◽

Metal Recovery ◽

Raw Material ◽

Protective Atmosphere ◽

Induction Melting ◽

Recovery Rates ◽

Recovery Yield ◽

High Efficient ◽

Machining Operations

Machining operations of cast parts usually generate considerable amounts of waste in the form of chips (usually 3–5% of the casting weight). Traditionally, swarf is sold to scrapers and remelters, but this option is quite expensive because the selling price is roughly 30% of the acquisition price of the commercial 2nd melt raw material. For most aluminium foundries that incorporate machining operations in their products, reusing aluminium chips as raw material for the melting stocks is perhaps the best option as waste management policy in what concerns to economical and technical aspects. Nevertheless, aluminium swarf is a low density product (0.25 kg/dm3) and is usually covered by a thin film of aluminium oxide and machining fluid. Melting such a product without suitable previous preparation leads to very low metal recovery rates, high energy consumption, gases and smoke generation and very low quality of the final product. During the last years, the authors have developed a high efficient and environmentally friend aluminium swarf recycling technique, using direct incorporation in aluminium melts. The influence of processing parameters, namely melt temperature and holding time, melting atmosphere, swarf briquetting pressure and melting charge composition in the metal recovery yield and dross generation was studied and characterized, and the optimal processing parameters were established. The microstructure of the final product obtained in those conditions was evaluated and is also presented. It is shown that the recycling efficiency depends on the swarf conditioning, the melting technique and the melt treatment methodology. Swarf moisture reduction, induction melting under protective atmosphere and a specially developed degassing technique were found the most important factors influencing the recycling process. By using the developed technique, cast ingots with microstructure and sanity similar to commercially available AlSi12Cu1 2nd melt raw material were successfully obtained with minimal dross formation and metal recovery rates around 90%, without using traditional salts and fluxes.

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Multiscale Copper-µDiamond Nanostructured Composites

Materials Science Forum ◽

10.4028/www.scientific.net/msf.730-732.925 ◽

2012 ◽

Vol 730-732 ◽

pp. 925-930

Author(s):

Daniela Nunes ◽

Vanessa Livramento ◽

Horácio Fernandes ◽

Carlos Silva ◽

Nobumitsu Shohoji ◽

...

Keyword(s):

Pure Copper ◽

Thermal Stabilization ◽

Hot Extrusion ◽

Processing Parameters ◽

High Energy ◽

X Ray Diffraction ◽

X Ray ◽

Optimal Processing ◽

Novel Approach ◽

Transmission Electron

Nanostructured copper-diamond composites can be tailored for thermal management applications at high temperature. A novel approach based on multiscale diamond dispersions is proposed for the production of this type of materials: a Cu-nDiamond composite produced by high-energy milling is used as a nanostructured matrix for further dispersion of micrometer sized diamond. The former offers strength and microstructural thermal stability while the latter provides high thermal conductivity. A series of Cu-nDiamond mixtures have been milled to define the minimum nanodiamond fraction suitable for matrix refinement and thermal stabilization. A refined matrix with homogenously dispersed nanoparticles could be obtained with 4 at.% nanodiamond for posterior mixture with mDiamond and subsequent consolidation. In order to define optimal processing parameters, consolidation by hot extrusion has been carried out for a Cu-nDiamond composite and, in parallel, for a mixture of pure copper and mDiamond. The materials produced were characterized by X-ray diffraction, scanning and transmission electron microscopy and microhardness measurements.

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Nanostructured Strontium-Doped Calcium Phosphate Cements: A Multifactorial Design

Applied Sciences ◽

10.3390/app11052075 ◽

2021 ◽

Vol 11 (5) ◽

pp. 2075

Author(s):

Massimiliano Dapporto ◽

Davide Gardini ◽

Anna Tampieri ◽

Simone Sprio

Keyword(s):

Calcium Phosphate ◽

Setting Time ◽

Processing Parameters ◽

High Energy ◽

Powder Particle Size ◽

Extrusion Force ◽

Precise Control ◽

Calcium Phosphate Cements ◽

Shear Mixing ◽

Mixing Techniques

Calcium phosphate cements (CPCs) have been extensively studied in last decades as nanostructured biomaterials for the regeneration of bone defects, both for dental and orthopedic applications. However, the precise control of their handling properties (setting time, viscosity, and injectability) still represents a remarkable challenge because a complicated adjustment of multiple correlated processing parameters is requested, including powder particle size and the chemical composition of solid and liquid components. This study proposes, for the first time, a multifactorial investigation about the effects of powder and liquid variation on the final performance of Sr-doped apatitic CPCs, based on the Design of Experiment approach. In addition, the effects of two mixing techniques, hand spatula (low-energy) and planetary shear mixing (high-energy), on viscosity and extrusion force were compared. This work aims to shed light on the various steps involved in the processing of CPCs, thus enabling a more precise and tailored design of the device, based on the clinical need.

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Plasma Spheroidized Alumina/Zircon Mixtures

Thermal Spray 2000: Proceedings from the International Thermal Spray Conference ◽

10.31399/asm.cp.itsc2000p0871 ◽

2000 ◽

Author(s):

Y. Li ◽

K.A. Khor

Keyword(s):

Thermal Spraying ◽

Processing Parameters ◽

High Energy ◽

Molten State ◽

Composite Powders ◽

Spray Process ◽

Plasma Spheroidization ◽

Plasma Spray Process ◽

Energy Ball ◽

Spheroidized Powder

Abstract The plasma-spray process is specified by the associated processing parameters, where these influence the properties of the resultant deposits. This article describes the preparation and processing of composite powders for use in thermal spraying by mixing high purity zircon and alumina powders. The spheroidized powder were obtained by high energy ball milling and rapid solidification from the molten state during plasma spraying. The article discusses the processes involved in spray drying and plasma spheroidization, describing thermal analysis and mullitization kinetics in the spheroidized alumina/zircon mixtures.

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Characterizing the Effect of Processing Parameters on Temperature Distribution of 7075 Aluminum Alloy Slurry Prepared by Enthalpy Control Process

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.327.263 ◽

2022 ◽

Vol 327 ◽

pp. 263-271

Author(s):

Gan Li ◽

Jin Kang Peng ◽

En Jie Dong ◽

Juan Chen ◽

Hong Xing Lu ◽

...

Keyword(s):

Aluminum Alloy ◽

Temperature Difference ◽

Initial Temperature ◽

Control Process ◽

Processing Parameters ◽

Heating Time ◽

7075 Aluminum Alloy ◽

Semi Solid ◽

7075 Alloy ◽

Slurry Preparation

There is a strong demand for high-strength aluminum alloys such as 7075 aluminum alloy to be applied for rheocasting industry. The overriding challenge for the application of 7075 alloy is that its solid fraction is very sensitive to the variation of temperature in the range of 40% ~ 50% solid fraction, which inevitably narrows down the processing window of slurry preparation for rheocasting process. Therefore, in this work, a novel method to prepare semi-solid slurry of the 7075 alloy, so called Enthalpy Control Process (ECP), has been developed to grapple with this issue. In the method, a medium-frequency electromagnetic field was applied on the outside of slurry preparation crucible to reduce the temperature difference throughout the slurry. The effect of processing parameters, including heating power, heating time, the initial temperature of crucible and melt weight, on the temperature field of the semi-solid slurry was investigated. The results exhibited that although the all the processing parameters had a great influence on the average temperature of the slurry, heating time was the main factor affecting the maximum temperature difference of the slurry. The optimum processing parameters during ECP were found to be heating power of 7.5 KW, the initial temperature of crucible of 30 °C ~ 200 °C and melt weight of 2 kg.

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