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The present work deals with the synthesis of some Al-based composites prepared by mechanical milling and processing by powder metallurgy followed by the evaluation of process conditions as: type of additive, their concentration and milling intensity studying its effect on the characteristics of the powder composite and mechanical performance of the composite. Powder samples were microstructural characterized by electronic microscopy (SEM–TEM) and the mechanical response was followed by hardness and compressive tests. A pronounced effect on the mechanical response of the specimens was evident after the addition of reinforced particles and milling intensity. Microscopy studies showed a uniform dispersion of the reinforcing particles in the metallic matrix at nanometric scale and an important grain refinement of the Al matrix was confirmed. After processing, a 66% increase on the mechanical response was reached with 1% of additive complemented with short milling intensities.
Aluminum (Al) based composites were produced by a solid state route using a high energy ball milling. Pure Al and mechanochemical processed graphite (C) powders were used as precursors. The C particles were prepared under different milling intensities and an additional chemical leaching process. Microscopy studies showed a uniform dispersion of the carbon nanoparticles into the aluminum matrix. A pronounced effect on the mechanical response of the specimens (σmax, σy and hardness) was evident upon the addition of the C particles. An optimum value on the mechanical response was reached with small amounts of C complemented with medium milling intensities. This effect is believed to be caused by the homogeneous dispersion of the carbon particles into the matrix. Higher C contents cause both: particle agglomeration and saturation of the matrix, which decreases the mechanical properties of samples.
The 2024 aluminum alloy produced from elemental powders and reinforced by the addition of carbon nanotubes were microstructural and mechanically characterized. Composites were synthesized through milling process followed by cold consolidation, sintering and hot extrusion. The effect of the nanotubes on the microstructure and mechanical properties were analyzed in the composites after T6 thermal treatment. Al4C3 formation was due to the reaction of carbon nanotubes and Al matrix. Precipitated Al–Cu phase coexists and presents interaction with crystallized carbide and dispersed nanotubes. There is a direct relationship of carbon nanotubes content and hardness answer.
Based.carbon reinforcements (BCR) are interesting materials capable to be applied in several fields in materials science. Because of their excellent chemical, physical and mechanical properties, they are widely applied in electronic, automotive and aircraft industry.
The wear behavior of the 2024 aluminum alloy and its composites was evaluated through a pin-on-disk system. For this purpose the aluminum alloy was reinforced by carbon nanotubes dispersion produced by milling process. The nanotubes dispersion was carried out using a high energy mill for a fixed milling time. Milled powders were cold consolidated, sintered and then microstructurally and mechanically evaluated. The wear behavior of the alloy and its composites was evaluated considering the different nanotube contents under several abrasive conditions. The composites with higher nanotube concentration (5.0 wt%) displayed an improved wear resistance in all cases evaluated in this work.
Aluminum-graphite-copper (Al-C-Cu) novel micro-composites have been produced using the Mechanical Alloying process (MA). The mechanical properties of the obtained composites have been evaluated. Yield strength (σy) values reached in the composites are considerably higher than those reported for pure aluminum. There is a direct relationship between σy and final graphite content in the composite. σy values increase as the nominal C content increases as well. We found that the most important hardening element was the graphite. We found that the optimal ratio Cu/C correspond to 0.33% for different volume fractions of graphite and cooper. There is an apparent synergy effect in σy between Cu and C. Results of TEM analysis have shown the presence of alumina particles in fiber shape from oxide surface of powder. Presence of alumina fibers in the composite improves the mechanical properties.
ALFREDO MARTINEZ GARCIA ANA KARIN NAVARRO MARTINEZ Christopher Neun Lkhamsuren Bayarjargal Wolfgang Morgenroth ERICK LOPEZ VAZQUEZ MIGUEL AVALOS BORJA Bjoern Winkler Erick Adrián Juárez Arellano (2019)
"The mechanosynthesis of hexagonal rhenium carbide (Re2C) from the elements is explored as a function of the balls to powder ratio (BPR). Burgios's equation has been used to calculate the accumulated energy (Delta E-accum) and the transferred energy per hit (Delta E-b). To get the complete mechanosynthesis of Re2C several conditions have to be met: BPR > 115: 1, Delta E-accum > 500 kJ/g, and Delta E-b > 2.656 x 10(-14) kJ. The reaction is completed after 30 min of milling if a BPR of 230: 1 is used. The pressure dependence of the unit-cell volume and the lattice parameters have been evaluated by synchrotron radiation diffraction using a diamond anvil cell up to 61(2) GPa. A fit of a 2nd-order Birch-Murnaghan equation of state results in a bulk modulus of B-0 = 374(3) GPa."
Carbon nanotube/2024 aluminum alloy (CNT/Al2024) composites were fabricated with a combination of mechanical alloying (MA) and powder metallurgy routes. Composites were microstructurally and mechanically evaluated at sintering condition. A homogeneous dispersion of CNTs in the Al matrix was observed by a field emission scanning electron microscopy. High-resolution transmission electron microscopy confirmed not only the presence of well dispersed CNTs but also needle-like shape aluminum carbide (Al4C3) crystals in the Al matrix. The formation of Al4C3 was suggested as the interaction between the outer shells of CNTs and the Al matrix during MA process in which crystallization took place after the sintering process. The mechanical behavior of composites was evaluated by Vickers microhardness measurements indicating a significant improvement in hardness as function of the CNT content. This improvement was associated to a homogeneous dispersion of CNTs and the presence of Al4C3 in the aluminum alloy matrix.
Aluminum/Graphite composites (Al/C composites) have the advantages of Al (light weight, easy
machinability and good heat conduction) in combination with the advantages of C whiskers (High
Youngs Modulus, small to negative CTE, high tensile strength and high thermal conductivity).
However, Metallographic analysis, EDX and microhardness profile revealed that fibers react with
molten aluminum to form the detrimental Al4C3 phase in the HAZ and fusion zone. In order to gain
information about temperature transformation and formation conditions, scanning electron microscopy,
and termochemistry analysis were used. For experiments, were used power density (I), pulse width (t),
frequency (F), travel speed (S) and filler material (M) as independent variables. Thereby, was found
that the main process variables that influence the formation of Al4C3 are pulse duration and welding
speed, and that the effect of these variables cannot be explained only by using a thermodynamic model,
requiring a subsequent kinetic analysis.
Composites of Al-6063 aluminum alloy powder reinforced with graphite particles were
prepared by mechanical milling, sintering and subsequent hot extrusion. Mechanical properties
and microstructural characterization were done as a function of graphite content. For lower graphite
contents mechanical resistance is increasing as the graphite content is increased as well; for
higher contents, graphite agglomeration reduces mechanical resistance. This variation is related
to the graphite dispersion / agglomeration into aluminum alloy matrix.
Dispersion, Graohite Nanoparticles, 6063 Aluminum Alloy, Mechanical Milling, Hot Extrusion INGENIERÍA Y TECNOLOGÍA CIENCIAS TECNOLÓGICAS TECNOLOGÍA DE MATERIALES PROPIEDADES DE LOS MATERIALES PROPIEDADES DE LOS MATERIALES