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

Metals ◽  
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.

scholarly journals Nickel Porous Compacts Obtained by Medium-Frequency Electrical Resistance Sintering

Materials ◽  
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.

scholarly journals Medium-Frequency Electrical Resistance Sintering of Soft Magnetic Powder Metallurgy Iron Parts

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 994
Author(s):  
Raquel Astacio ◽  
Fátima Ternero ◽  
Jesús Cintas ◽  
Francisco G. Cuevas ◽  
Juan Manuel Montes
Keyword(s):  
Powder Metallurgy ◽  
Electrical Resistance ◽  
Low Voltage ◽  
Vacuum Furnace ◽  
Soft Magnetic ◽  
Medium Frequency ◽  
Joule Effect ◽  
Simultaneous Application ◽  
Cold Pressing ◽  
Furnace Sintering

The fabrication of soft magnetic Fe parts by the medium-frequency electrical resistance sintering (MF-ERS) technique is studied in this paper. This consolidation technique involves the simultaneous application to metallic powders of pressure and heat, the latter coming from the Joule effect of a low-voltage and high-intensity electric current. Commercially pure iron powder was used in the consolidation experiences. The porosity distribution, microhardness, electrical resistivity and hysteresis curves of the final compacts were determined and analysed. The results obtained were compared both with those of compacts consolidated by the conventional powder metallurgy (PM) route of cold pressing and vacuum furnace sintering, and with fully dense compacts obtained by double cycle of cold pressing and furnace sintering in hydrogen atmosphere.

Consolidation of Titanium Powder by Electrical Resistance Sintering: Practice and Simulation

2021 ◽  
Vol 876 ◽  
pp. 1-6
Author(s):  
Fátima Ternero Fernández ◽  
Petr Urban ◽  
Raquel Astacio Lopez ◽  
Rosa M. Aranda Louvier ◽  
Francisco G. Cuevas
Keyword(s):  
Electrical Resistance ◽  
Titanium Powder ◽  
Low Voltage ◽  
Pure Titanium ◽  
Commercially Pure Titanium ◽  
Consolidation Process ◽  
Simultaneous Application ◽  
Microhardness Distribution ◽  
Powder Mass ◽  
Furnace Sintering

In this work, a commercially pure titanium powder has been consolidated using the Electrical Resistance Sintering (ERS) process. This technique consists in the consolidation of a powder mass by the simultaneous application of pressure (80 MPa, in this work) and heating caused by the passage of a high intensity (3.5-6.0 kA, in this case) and low voltage current (lower than 10 V), during short dwelling times (0.8-1.6 s, in this work). The resulting compacts have been mechanically characterised by measuring their microhardness distribution. The results obtained are compared with the corresponding values of compacts prepared with the same powders following the conventional P/M route of cold pressing and furnace sintering. The results of some simulations are provided to give information about the temperatures reached inside the compacts during the electrical consolidation process.

Medium-Frequency Electrical Resistance Sintering of Highly Oxidized Iron Powder

2018 ◽  
Vol 772 ◽  
pp. 113-117
Author(s):  
Raquel Astacio ◽  
Fatima Ternero ◽  
Eduardo Sanchez Caballero ◽  
Juan Manuel Montes ◽  
Francisco Gomez Cuevas
Keyword(s):  
Electrical Resistance ◽  
Processing Parameters ◽  
High Energy ◽  
Heating Time ◽  
Current Intensity ◽  
Medium Frequency ◽  
Consolidation Process ◽  
Oxidized Iron ◽  
Hardness Change ◽  
Compression Resistance

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.

scholarly journals Effect of Applied Pressure on the Electrical Resistance of Carbon Nanotube Fibers

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2106
Author(s):  
Chris J. Barnett ◽  
James D. McGettrick ◽  
Varun Shenoy Gangoli ◽  
Ewa Kazimierska ◽  
Alvin Orbaek White ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Electrical Resistance ◽  
Copper Wire ◽  
Applied Pressure ◽  
Radial Strain ◽  
Electrical Current ◽  
Electrical Contacts ◽  
Electrical Performance ◽  
Macro Scale ◽  
Carbon Nanotube Fibers

Carbon nanotubes (CNTs) can be spun into fibers as potential lightweight replacements for copper in electrical current transmission since lightweight CNT fibers weigh <1/6th that of an equivalently dimensioned copper wire. Experimentally, it has been shown that the electrical resistance of CNT fibers increases with longitudinal strain; however, although fibers may be under radial strain when they are compressed during crimping at contacts for use in electrical current transport, there has been no study of this relationship. Herein, we apply radial stress at the contact to a CNT fiber on both the nano- and macro-scale and measure the changes in fiber and contact resistance. We observed an increase in resistance with increasing pressure on the nanoscale as well as initially on the macro scale, which we attribute to the decreasing of axial CNT…CNT contacts. On the macro scale, the resistance then decreases with increased pressure, which we attribute to improved radial contact due to the closing of voids within the fiber bundle. X-ray photoelectron spectroscopy (XPS) and UV photoelectron spectroscopy (UPS) show that applied pressure on the fiber can damage the π–π bonding, which could also contribute to the increased resistance. As such, care must be taken when applying radial strain on CNT fibers in applications, including crimping for electrical contacts, lest they operate in an unfavorable regime with worse electrical performance.

CFD Simulation and Experimental Validation of Solidification of Metal Matrix Composites (MMC) in the Presence of Cooled Fibers

2004 ◽  
Author(s):  
R. S. Amano ◽  
J. Xie ◽  
E. K. Lee ◽  
P. K. Rohatgi
Keyword(s):  
Metal Matrix Composites ◽  
Metal Matrix ◽  
Cfd Simulation ◽  
Applied Pressure ◽  
Casting Process ◽  
Processing Parameters ◽  
Matrix Composites ◽  
Primary Alpha ◽  
Parametric Studies ◽  
Solidification Of Metal

A new experimental configuration for the casting of metal matrix composites (MMCs) using Al-4.5 wt pct Cu have been used to obtain finer microstructures around the fiber reinforcement. The new configuration allows the fibers to be extended out the mold and cooled by a heat sink. By doing so, the solidification can be made more rapid, and more primary alpha-aluminum phase can be formed on the surface of the fibers. It is believed that this can lead to improvement in the properties of the composite. CFD simulation of the solidification of Al-4.5 wt pct Cu in the casting process has been carried out by using commercial CFD code. Parametric studies on the effects of different processing parameters on solidification time have been simulated using the CFD code. These parameters include, but are not limited to, the pouring temperature of the liquid melt, sink temperature, fiber length extended out of the mold, the mold initial temperature, fiber conductivity, applied pressure, and fiber bundle diameter. Selected simulation results are compared with the available experimental data obtained from the UWM Center for Composites.

Deformation Induced Percolating Porosity In High Pressure Torsioned (HPT) Copper

2011 ◽  
Vol 702-703 ◽  
pp. 105-108 ◽  
Author(s):  
Matthias Wegner ◽  
Jörn Leuthold ◽  
Sergiy V. Divinski ◽  
Daria Setman ◽  
Michael Zehetbauer ◽  
...  
Keyword(s):  
High Pressure ◽  
Impurity Concentration ◽  
High Pressure Torsion ◽  
Applied Pressure ◽  
Processing Parameters ◽  
Tracer Method ◽  
Radiotracer Technique ◽  
Degree Of Deformation ◽  
Radio Tracer ◽  
Structural Aspects

Copper of different purity levels (4N, 5N) produced by High Pressure Torsion (HPT) with varying processing parameters is investigated utilizing the radiotracer technique. While the degree of deformation is constant, the effect of the applied quasi-hydrostatic pressure and of the impurity concentration on the as deformed samples is analysed. By applying the radio tracer method micro structural aspects are revealed that are not easily accessible by conventional methods. The measurements indicate the formation of a percolating porosity during the HPT process as a function of the applied pressure and (although less pronounced) of the impurity concentration.

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

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.

Electroactive Paper Materials Coated With Carbon Nanotubes and Conducting Polymers

Aerospace ◽  
2005 ◽  
Author(s):  
Jaehwan Kim ◽  
Zoubeida Ounaies ◽  
Sung-Ryul Yun ◽  
Yukeun Kang ◽  
Seung-Hun Bae
Keyword(s):  
Carbon Nanotubes ◽  
Low Voltage ◽  
Artificial Muscle ◽  
Processing Parameters ◽  
Single Wall Carbon Nanotubes ◽  
Gold Electrodes ◽  
Force Output ◽  
Final Performance ◽  
Low Voltage Operation ◽  
Muscle Actuators

Electro-Active Paper (EAPap) materials based on cellulose are attractive for many applications because of their low voltage operation, lightweight, dryness, low power consumption, bio-degradable. The construction of EAPap actuator has been achieved using the cellulose paper film coated with thin electrode layers. This actuator showed a reversible and reproducible bending movement. In order to improve both force and displacement of this, EAPap actuator efforts are made to construct the device using increasing number of complementary conducting polymer layers and carbon nanotubes. A hybrid EAPap actuator is developed using single-wall carbon nanotubes (CNT)/Polyaniline (PANi) electrodes, as a replacement to gold electrodes. It is expected that the use of CNT can enhance the stiffness of the tri-layered actuator, thus improving the force output. Furthermore, the presence of the CNT may increase the actuation performance of the EAPap material. CNT is dispersed in NMP(1-Methyl-2-pyrrolidine), and the resulting solution is used as a solvent for PANi. The CNT/PANi/NMP solution is then cast on the EAPap by spin coating. The coated EAPap is dried in an oven. The effect of processing parameters on the final performance of the CNT/PANi electrodes is assessed. The final performance of the electrodes is quantified in terms of the electrical conductivity under dc and ac measurement conditions. The actuation output of the CNT/PANi/EAPap samples is tested in an environmental chamber in terms of free displacement and blocked force. The performance of the hybrid actuators is also investigated in terms of frequency, voltage, humidity and temperature to help shed light on the mechanism responsible for actuation. Comparison of these results in that of the EAPap with PANi and gold electrodes are also accomplished. EAPap materials are bio-degradable that is important property for artificial muscle actuators for biomimetic with controlled properties and shape.

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