Autor: ROBERTO MARTINEZ SANCHEZ

Simultaneous effect of mechanical alloying and arc-melting processes in the microstructure and hardness of an AlCoFeMoNiTi high-entropy alloy

ROBERTO MARTINEZ SANCHEZ (2015)

A nanostructured AlCoFeMoNiTi high entropy alloy was synthesized through the mechanical alloying process. Bulk samples were obtained by two different routes to compare the microstructural evolution and hardness behavior: sintering and arc melting. Through electron microscopy analyses the formation of Mo-rich and Ti-rich phases were identified in the melted sample, while Ti-rich nano-precipitates were observed in the sintered sample. A higher microhardness value was achieved on the sintered sample than for the melted sample. The disadvantage of porosity in the sintered sample in comparison to the melted one was overcome by the hardening effect produced by the mechanical alloying.

Artículo

High entropy alloys; Mechanical alloying; Arc melting; Microstructure BIOLOGÍA Y QUÍMICA QUÍMICA

AlCoCuCrFeNiTi High Entropy Alloys Synthesized by Mechanical Alloying

CYNTHIA DEISY GOMEZ ESPARZA WILBER ANTUNEZ FLORES ROBERTO MARTINEZ SANCHEZ CARLOS ELIAS ORNELAS GUTIERREZ JOSE GERARDO CABAÑAS MORENO IVANOVICH ESTRADA GUEL JOSE MARTIN HERRERA RAMIREZ (2012)

Polvos elementales fueron mezclados y mecánicamente aleados para obtener tres aleaciones equiatómicas de alta entropía, NiCoAlFeCu, NiCoAlFeCuCr y NiCoAlFeCuCrTi. Los polvos fueron compactados y sinterizados a 1200 ºC. En las tres aleaciones sinerizadas, se observa la formación de al menos dos fases. En cada una está presente una fase rica en Cu, que se puede relacionar con la segregación de Cu reportada en las investigaciones realizadas por la ruta líquida. Los resultados de microdureza Vickers revelan que las fases ricas en Cu son las que presentan los valores mínimos de dureza.

Artículo

Aleación CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA QUÍMICA FÍSICA OTRAS

Effect of milling time and CNT concentration on hardness of CNT/Al2024 composites produced by mechanical alloying

ROBERTO MARTINEZ SANCHEZ MARIO MIKI YOSHIDA LILIANA LICEA JIMENEZ IVANOVICH ESTRADA GUEL (2013)

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.

Artículo

Aluminum; CNT; Mechanical alloying; Composites; Sintering BIOLOGÍA Y QUÍMICA QUÍMICA

Microstructural and hardness behavior of graphene-nanoplatelets/aluminum composites synthesized by mechanical alloying

ROBERTO MARTINEZ SANCHEZ (2014)

Graphene can be considered as an ideal reinforcement for the production of composites due to its outstanding mechanical properties. These characteristics offer an increased opportunity for their study in the production of metal matrix composites (MMCs). In this research, the studied composites were produced by mechanical alloying (MA). The employed milling times were of 1, 3 and 5 h. GNPs were added in 0.25, 0.50 and 1.0 wt% into an aluminum powder matrix. Milled powders were cold consolidated and subsequently sintered. Composites were microstructurally characterized with Raman spectroscopy and electron microscopy and X-ray diffraction. The hardness behavior in composites was evaluated with a Vickers micro-hardness test. A homogeneous dispersion of graphene during MA and the proper selection of sintering conditions were considered to produce optimized composites. The obtained results with electron microscopy indicate a homogeneous dispersion of GNPs into the aluminum matrix. Analyses showed GNPs edges where the structure of the graphene layers conserved after MA is observed.

Artículo

BIOLOGÍA Y QUÍMICA QUÍMICA