Showing papers on "Powder metallurgy published in 2012"
TL;DR: In this paper, a strategy called flake powder metallurgy (flake PM) was used to achieve a uniform distribution of carbon nanotubes (CNTs) in CNT/Al composites and thus realize the potential of CNTs as a reinforcement.
338 citations
TL;DR: In this paper, the carbon nanotube (CNT)/aluminum composites were fabricated by a combination of powder metallurgy and subsequent friction stir processing (FSP), and microstructural observations indicated that the CNTs were singly dispersed in the composites.
251 citations
TL;DR: In this article, the fabrication of open cellular titanium foams by using an innovative spacer through powder metallurgy was investigated, and the porosities and pore structures were investigated by SEM.
146 citations
TL;DR: In this article, a significant enhancement in the thermoelectric figure-of-merit of phosphorous doped nanostructured n-type Si80Ge20 alloys, which were synthesized employing high energy ball milling followed by rapid heating using spark plasma sintering, was reported.
Abstract: We report a significant enhancement in the thermoelectric figure-of-merit of phosphorous doped nanostructured n-type Si80Ge20 alloys, which were synthesized employing high energy ball milling followed by rapid-heating using spark plasma sintering. The rapid-heating rates, used in spark plasma sintering, allow the achievement of near-theoretical density in the sintered alloys, while retaining the nanostructural features introduced by ball-milling. The nanostructured alloys display a low thermal conductivity (2.3 W/mK) and a high value of Seebeck coefficient (−290 μV/K) resulting in a significant enhancement in ZT to about 1.5 at 900 °C, which is so far the highest reported value for n-type Si80Ge20 alloys.
138 citations
TL;DR: In order to combine high tensile strength and ductile behavior, carbon nanotube (CNT)/Al nanolaminated composites with alternating layers of Al (∼400-nm) and CNTs ( ∼50-nm), were fabricated by flake powder metallurgy.
134 citations
TL;DR: In this paper, the cold compaction pressure was varied between 75 and 125 MPa in order to examine its effect on density, cenosphere crushing and strength of Ti-cenosphere foam.
117 citations
TL;DR: In this paper, the authors investigated the wear and friction that occurs between copper-based composites and copper under dry sliding conditions and found that materials with MoS 2 and MoSe 2 had a coefficient of friction close to 0.2, undetectable linear wear under a contact pressure of less than 0.255
108 citations
30 May 2012-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, a high-energy planetary ball mill was used to produce Al 5083/10.43% SiCp (Al 5083 /SiCp) nanocomposite.
Abstract: Al 5083 alloy powder with 10 wt.% (∼8.43 vol.%) of silicon carbide (SiCp) nanoparticulates having size of ∼20 nm were milled using a high-energy planetary ball mill to produce Al 5083/10 wt.% SiCp (Al 5083/SiCp) nanocomposite. Subsequently, the milled powders were consolidated and sintered by employing spark plasma sintering (SPS) technique in order to attain the near theoretical densification while retaining the nanostructure of Al 5083 matrix embedded with uniformly distributed SiCp. High resolution transmission microscopy (HR-TEM) analysis revealed the grain morphology and grain size of the Al 5083 matrix along with the interfacial microstructure between Al 5083 matrix and SiCp particulates. The crystallite size of ball milled Al 5083 matrix was observed to be ∼25 nm and was coarsened up to 30 nm after rapid consolidation and sintering using SPS. Compressive strength and elastic modulus of Al 5083/SiCp metal matrix nanocomposites was significantly increased to that of the un-reinforced Al 5083 alloy. Nanoindentation measurements on these nanocomposites demonstrated the hardness of ∼280 HV with an elastic modulus of 126 GPa.
106 citations
TL;DR: In this article, a pure titanium matrix composite reinforced with carbon nanotubes (CNTs) was prepared by spark plasma sintering and hot extrusion via powder metallurgy process.
103 citations
TL;DR: In this article, a homogeneous dispersion of the nanotubes at the micron scale is required in order to improve the mechanical properties of the metal matrix composite, which can be achieved using ball-milling through the mechanisms of plastic deformation and cold-welding.
15 Mar 2012-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the microstructure of the obtained composite was investigated using light microscopy, scanning electron microscopy and transmission electron microscope using 3-point bend test, which showed that the composite starts to show ductile behavior approximately at 400 degrees C and the bending stress continuously decreases from 200 degrees C to 1000 degrees C. The hardness of the composite was found to be 4.9 GPa at 10 N load.
Abstract: A W-2Y(2)O(3) composite is produced by powder metallurgy, including the pressing of the mixed elemental powders, their sintering and hot forging. The microstructure of the obtained composite is investigated using light microscopy, scanning electron microscopy and transmission electron microscopy. It appears that the material is composed of W grains having a mean size of 1-2 mu m and Y2O3 particles having a mean size of 300 nm to 1 mu m. The W grains contain a high density of dislocations. The mechanical properties of this material are investigated using nanoindentation and 3-point bend test. Berkovich hardness value is found to be 4.9 GPa at 10 N load, which is similar to that of pure W. 3-Point bend test shows that the composite starts to show ductile behavior approximately at 400 degrees C and the bending stress continuously decreases from 200 degrees C to 1000 degrees C. (C) 2012 Elsevier B.V. All rights reserved.
TL;DR: In this article, the evolution of microstructure, density and hardness of Cu-Al2O3 metal matrix composites with different techniques of sintering have been demonstrated, and the effect of Sintering atmosphere on the interfacial compatibility of matrix and reinforcement has also been discussed.
TL;DR: In this article, the effects of different sintering temperatures on the mechanical properties of four aluminum-graphite alloys were reported Different percentages of exfoliated graphite nanoplatelets particles (xGnP) were added to pure aluminum by using the powder metallurgy technique.
15 Mar 2012-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the effects of mechanical alloying time and CNT dispersion on the microstructure and mechanical properties of the metal-CNT composite have not been fully investigated.
Abstract: For powder-based metal composite manufacturing, mechanical alloying has been widely used to disperse the clustered carbon nanotubes (CNTs) in the metal matrix. However, the effects of mechanical alloying time and CNT dispersion on the microstructure and mechanical properties of the metal–CNT composite have not been fully investigated. In this study, aluminum alloy 6061 (Al6061)–CNT composites were synthesized by semi-solid powder processing from powders that had been mechanically alloyed for different durations. The powder morphology, microstructure, hardness, flexural strength, fracture surface, and composition of the Al6061–CNT composites were analyzed. The results showed that the multi-walled CNT agglomerates were first crushed into thin layers and then dispersed during the mechanical alloying procedure. The CNTs on the surfaces of Al6061 particles at various mechanical alloying times showed that the CNT length decreased quickly to about 1.2 μm after 1 h of mechanical alloying and below 1 μm after 3 h from the original length of over 5 μm. The grains of the Al6061–CNT composites deformed severely during the mechanical alloying process. The hardness improved as the mechanical alloying time increased. However, the bend test and fracture surface indicated reduction of the composite ductility with increasing mechanical alloying time. Compositional analysis also showed formation of aluminum carbide (Al 4 C 3 ) due to the CNT addition. In addition, a modified shear lag model was used to predict the strength of Al6061–CNT at different mechanical alloying times.
TL;DR: In this article, the thermal conductivity of metal powders with different particle diameters and their mixture was analyzed using a theoretically verified method, and its relation to porosity was elaborated.
Abstract: Selective Laser Melting (SLM) is a direct fabrication of part through layer by layer powder deposition and successive laser beam irradiation based on Computer Aided Design (CAD) data. One of the important properties in SLM is thermal conductivity of metal powder. This is because the ability of metal powder to conduct heat will affect the consolidation process during SLM. In this paper, thermal conductivity of metal powders with different particle diameters and their mixture was analysed. Other than that, thermal conductivity of consolidated materials fabricated via SLM process was also studied. In order to measure the thermal conductivity of metal powder, a theoretically verified method which was previously developed by the authors was used. Determination of thermal conductivity of consolidated material was analysed using laser flash technique. It was found that the thermal conductivity of powder metal was influenced by bulk density and particle diameter of metal powder. In this study also, metal powders of different particle diameters were mixed with various volume ratios, and its effect was discussed. Thermal conductivity of the consolidated materials was also examined, and its relation to porosity was elaborated.
TL;DR: In this paper, the mechanical properties of copper were enhanced by adding 1.5% SiC particles into the matrix of the powder metallurgy method and sintering was performed in an open atmospheric furnace at 700°C for 2 hours.
Abstract: In this study mechanical properties of copper were enhanced by adding 1 wt.%, 2 wt.%, 3 wt.% and 5 wt.% SiC particles into the matrix. SiC particles of having 1 μm, 5 μm and 30 μm sizes were used as reinforcement. Composite samples were produced by powder metallurgy method and sintering was performed in an open atmospheric furnace at 700 °C for 2 h. Optical and SEM studies showed that the distribution of the reinforced particle was uniform. XRD analysis indicated that the dominant components in the sintered composites were Cu and SiC. Relative density and electrical conductivity of the composites decreased with increasing the amount of SiC and increased with increasing SiC particle size. Hardness of the composites increased with both amount and the particle size of SiC particles. A maximum relative density of 98% and electrical conductivity of 96% IACS were obtained for Cu–1 wt.% SiC with 30 μm particle size.
TL;DR: In this article, the effect of volume fraction of porosities on the thermal conductivity of pure copper was analyzed. But, the porosity is inherently introduced in these material systems, and adversely affects the composite material, among other factors including interfaces and reinforcement distribution.
TL;DR: In this article, the surface modification of aluminum workpiece by electric discharge coating (EDC) process using TiC/Cu green compact tool-electrode was presented, where the effect of input parameters (peak current, pulse-on-time, composition and compaction pressure of the tool-Electrode) on process performance parameters (roughness and micro-hardness of workpiece surface and coating layer thickness) were investigated.
Abstract: This article presents the surface modification of aluminum workpiece by electric discharge coating (EDC) process using TiC/Cu green compact tool-electrode. Powder metallurgy (P/M) tool-electrodes were used to create hard layer(s) on the workpiece surface by a material transfer from this tool-electrode (produced with powder metallurgy) to the workpiece surface it was possible to create hard layer(s) there with high tribological properties and integrity. The present study has been carried out to investigate the effect of input parameters (peak current, pulse-on time, composition and compaction pressure of the tool-electrode) on process performance parameters (roughness and micro-hardness of workpiece surface and coating layer thickness). Regression models have been developed to define a mathematical correlation between input and process performance parameters. Analysis of variance has been conducted at the 95% confidence level, to test the significance of these models. The results of the experiments indicat...
TL;DR: In this article, a new powder metallurgy process to make alumina parts through indirect selective laser sintering (SLS) is assessed, where density measurements, some geometrical assessments and scanning electron microscopy microstructural analyses are performed after each stage of the process, allowing an objective overview to be provided of the challenges and possibilities for the processing of high density technical ceramic parts through SLS of ball milled alumina/polyamide powder agglomerates.
Abstract: Purpose – The purpose of this paper is to assess a new powder metallurgy process to make alumina parts through indirect selective laser sintering (SLS). Density measurements, some geometrical assessments and scanning electron microscopy (SEM) microstructural analyses are performed after each stage of the process, allowing an objective overview to be provided of the challenges and possibilities for the processing of high density technical ceramic parts through SLS of ball milled alumina/polyamide powder agglomerates.Design/methodology/approach – The powder production by ball milling, SLS, cold isostatic pressing (CIP) or quasi isostatic pressing (QIP), debinding and sintering (FS) stages of the powder metallurgy process were sequentially investigated.Findings – Alumina parts with a density up to 94.1 per cent could be produced by a powder metallurgy process containing an SLS step. Microstructural investigation of the sintered samples reveals an alumina matrix with a grain size of ∼5 μm and two different ki...
TL;DR: In this article, a detailed characterisation of titanium-titanium boride composites processed by three powder metallurgy techniques, namely, hot isostatic pressing, spark plasma sintering and vacuum Sintering, was conducted.
15 May 2012-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the mechanical properties and corrosion behavior of an Mg-Al-Mn-Ca alloy produced by spinning water atomization process (SWAP) were investigated and compared to those of the alloys made by gravity cast and hot extrusion.
Abstract: The mechanical property and in particular the corrosion behavior of an Mg–Al–Mn–Ca alloy produced by spinning water atomization process (SWAP) were investigated and compared to those of the alloys made by gravity cast and hot extrusion. It is found that the SWAPed alloy has not only superior mechanical properties but also distinguished corrosion resistance. The corrosion resistance of the SWAPed alloy is about 2.5 and 10 times higher than that of the hot-extruded and as-cast alloys, respectively, when immersed in 0.1 M NaCl solution. Potentiodynamic polarization shows that both the anodic and cathodic current densities of the three alloys in 0.1 M NaCl solution are in the order of SWAPed alloy
23 Mar 2012
TL;DR: Powder injection molding (PIM) as discussed by the authors is a technology for manufacturing complex, precision, netshape components from either metal or ceramic powder, which can combine multiple parts into a single one, and overcomes the dimensional and productivity limits of isostatic pressing and slip casting, defects and tolerance limitations of investment casting, the mechanical strength of die-cast parts.
Abstract: Powder injection molding (PIM) is a technology for manufacturing complex, precision, netshape components from either metal or ceramic powder. The potential of PIM lies in its ability to combine the design flexibility of plastic injection molding and the nearly unlimited choice of material offered by powder metallurgy, making it possible to combine multiple parts into a single one (Hausnerova, 2011). Furthermore, PIM overcomes the dimensional and productivity limits of isostatic pressing and slip casting, the defects and tolerance limitations of investment casting, the mechanical strength of die-cast parts, and the shape limitation of traditional powder compacts (Tandon, 2008).
TL;DR: In this article, an optimized mechanical milling and hot pressing method was used to produce nanostructured Al2024 composites, which achieved an endothermic peak at ∼632°C due to Al 2024 melting and exothermic peaks between 645 and 658°C related to Al and MWCNTs reaction.
TL;DR: In this article, the sintering of a synthesized p-type Bi2Te3 nano-powder has been investigated by three different techniques, such as Hot Isostatic Pressing (HIP), microwave Sintering and Spark Plasma Sinterings (SPS) in terms of parameters such as temperature, pressure and power, microstructure and thermoelectric properties.
TL;DR: Physical, chemical, and mechanical characterizations of porous titanium implants made by an additive manufacturing method are described to gain insight into the correlation of process parameters and final physical properties of implants used in orthopedics.
Abstract: This article describes physical, chemical, and mechanical characterizations of porous titanium implants made by an additive manufacturing method to gain insight into the correlation of process parameters and final physical properties of implants used in orthopedics For the manufacturing chain, the powder metallurgy technology was combined with the additive manufacturing to fabricate the porous structure from the pure tanium powder A 3D printing machine was employed in this study to produce porous bar samples A number of physical parameters such as titanium powder size, polyvinyl alcohol (PVA) amount, sintering temperature and time were investigated to control the mechanical properties and porosity of the structures The produced samples were characterized through porosity and shrinkage measurements, mechanical compression test and scanning electron microscopy (SEM) The results showed a level of porosity in the samples in the range of 31–43%, which is within the range of the porosity of the cancelluous bone and approaches the range of the porosity of the cortical bone The results of the mechanical test showed that the compressive strength is in the wide range of 56–509 MPa implying the effect of the process parameters on the mechanical strengths This technique of manufacturing of Ti porous structures demonstrated a low level of shrinkage with the shrinkage percentage ranging from 15 to 5% © 2012 Wiley Periodicals, Inc J Biomed Mater Res Part B: Appl Biomater, 2012
TL;DR: In this article, a novel process called hydrogen sintering and phase transformation (HSPT) was proposed to produce near-fully dense Ti materials with very fine grain size (1.0µm) in as-sintered state.
Abstract: Titanium powder is typically sintered in high vacuum to achieve high density and low oxygen. Sintered materials usually have coarse grain size or coarse lamellar structure if it is the Ti–6Al–4V alloy. A novel process—hydrogen sintering and phase transformation (HSPT)—for sintering Ti in hydrogen is studied in this paper that can produce near-fully dense (>99%CP-Ti, >98%Ti–6Al–4V) Ti materials with very fine grain size (<1.0µm) in as-sintered state. This presents a potential opportunity for low cost manufacturing of powder metallurgy Ti materials with superior mechanical properties.
01 Jan 2012-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the effects of phase volume content, processing conditions, the size of aluminum particles, and porosity, on the physical and thermo-mechanical properties of an alumina reinforced aluminum composite in 25-450°C temperature range were determined.
Abstract: The objective of this study is to determine the effects of phase volume content, processing conditions, the size of aluminum particles, and porosity, on the physical and thermo-mechanical properties of an alumina reinforced aluminum composite in 25–450 °C temperature range. Composites with 0%, 5%, 10%, 20% and 25% volume contents of alumina are manufactured using powder metallurgy technique. Two types of composites with different aluminum powders were manufactured: composite A – 99.97% pure Al with 7–15 μm particles, and composite B – 97.5% pure Al powder with 3–4.5 μm particles. For both composites A and B, alumina powder with
TL;DR: In this paper, the effect of SiC content and particle size on the relative density, hardness and electrical conductivity of composites was investigated and the relative densities of Cu-SiC composites sintered at 700°C for 2h were obtained.
TL;DR: In this paper, a detailed transmission electron microscopy analysis has revealed that small additions of yttrium hydride to a powder metallurgy Ti 2.25Mo 1.5Fe alloy resulted in the formation of both chlorine-free yttium oxides and essentially oxygen-free Yttrium chlorides.