Autor: ROBERTO MARTINEZ SANCHEZ

Wear behavior in Al2024–CNTs composites synthesized by mechanical alloying

JOSE LUIS BUENO ESCOBEDO IVANOVICH ESTRADA GUEL MARIO MIKI YOSHIDA LILIANA LICEA JIMENEZ ROBERTO MARTINEZ SANCHEZ (2012)

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.

Artículo

Carbon nanotubes; Aluminum; Composites; Milling process; Abrasive wear; Pin-on-disc QUÍMICA

Effect of carbon nanoparticles addition on the mechanical properties of an aluminum composite prepared by mechanical milling and leaching process

IVANOVICH ESTRADA GUEL CALEB CARREÑO GALLARDO ROBERTO MARTINEZ SANCHEZ (2012)

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.

Artículo

Aluminum; Composites; Graphite; High energy milling QUÍMICA

Microstructural and magnetic behavior of an equiatomic NiCoAlFe alloy prepared by mechanical alloying

JOSE MARTIN HERRERA RAMIREZ ROBERTO MARTINEZ SANCHEZ IVANOVICH ESTRADA GUEL JOSE ANDRES MATUTES AQUINO (2014)

Equiatomic NiCoAlFe powder alloys were synthesized by mechanical alloying. The microstructural evolution of the mechanically alloyed powders at different times was followed with X-ray diffraction and scanning electron microscopy. The as-mechanically alloyed powders were subjected to a rapid annealing treatment at 1273 K and 1473 K during 3 min in vacuum. X-ray diffraction studies show the structure of both, the as-mechanically alloyed and annealed powders, consisted in a mixture of nanocrystalline simple phases (FCC + BCC). Crystallite size, after annealing, still remained in nanoscale. Coercivity increased due to the decrease in crystallite size and because of the defects caused by mechanical alloying in the as-mechanically alloyed samples; then coercivity decreased due to the phenomenon of random magnetic anisotropy and tended to stabilize with longer alloying times. A similar behavior was observed in annealed samples at 1273 K. However, random magnetic anisotropy was not observed after annealing at 1473 K because crystals with larger sizes were produced, and a steady increase in coercivity was observed.

Artículo

BIOLOGÍA Y QUÍMICA

Mechanical properties of the A356 aluminum alloy modified with La/Ce.

EDUARDO AGUIRRE DE LA TORRE ROBERTO MARTINEZ SANCHEZ JAVIER CAMARILLO CISNEROS CYNTHIA DEISY GOMEZ ESPARZA RAUL PEREZ BUSTAMANTE HANSEL MANUEL MEDRANO PRIETO (2013)

The research of rare earths for the synthesis of materials with improved mechanical performance is of great interest when they are considered for potential applications in the automotive industry. In this regard, the effect on the mechanical properties and microstructure of the automotive A356 aluminum alloy reinforced with 0.2 (wt.%) Al-6Ce-3La (ACL) was investigated. The ACL was added to the melted A356 alloy in the as-received condition and processed by mechanical milling. In the second route, the effect of the ACL processed by mechanical milling and powder metallurgy techniques was investigated, and compared with the results obtained from the A356 alloy strengthened with ACL in the as-received condition. Microstructural properties were evaluated by means of X-ray diffraction in order to observe the solubility of Ce/La in the Al matrix. In addition, electron microscopy was employed in order to investigate the effect of milling time on the size and morphology of La/Ce phase under milling process. Mechanical properties of the A356 alloy modified with ACL were measured by hardness and tensile test. For comparison unmodified specimens of the A356 were characterized according to the previous procedure. The microstructural and mechanical characterization was carried out in specimens after solution and artificial aging. Observations in scanning electron microscopy indicated a homogeneous dispersion of La/Ce phases by using both routes; however, mechanical results, in the modified A356 alloy with the ACL in the as-received condition, showed an improvement in the mechanical performance of the A356 alloy over that reinforced with the ACL mechanically milled.

Artículo

A356; rare earths; mechanical milling; mechanical properties QUÍMICA

Dispersion of sDispersion of silicon carbide nanoparticles in a AA2024 aluminum alloy by a high-energy ball millilicon carbide nanoparticles in a AA2024 aluminum alloy by a high-energy ball mill

ROBERTO MARTINEZ SANCHEZ IVANOVICH ESTRADA GUEL (2014)

Al2024 alloy was reinforced with silicon carbide nanoparticles (SiCNP), whose concentration was varied in the range from 0 to 5 wt.%; some composites were synthesized with the mechanical milling (MM) process. Structure and microstructure of the consolidated samples were studied by X-ray diffraction and transmission electron microscopy, while mechanical properties were investigated by compressive tests and hardness measurements. The microstructural evidence shows that SiCNP were homogeneously dispersed into the Al2024 alloy using high-energy MM after 2 h of processing. On the other hand, an increase of the mechanical properties (yield stress, maximum strength and hardness) was observed in the synthesized composites as a direct function of the SiCNP content. In this research several strengthening mechanisms were observed, but the main was the obstruction of dislocations movement by the addition of SiCNP.

Artículo

QUÍMICA