Strengthening Mechanisms of Aluminum Matrix Nanocomposites Reinforced with CNTs Produced by Powder Metallurgy

Abstract

The present work aims to investigate the strengthening mechanisms in aluminum matrix nanocomposites reinforced by carbon nanotubes (CNTs). A classical powder metallurgy route produced Al-CNT nanocomposites using ultrasonication and ball milling as dispersion/mixture techniques. The microstructural characterization is crucial for this study to reach the objective, being performed mainly by electron backscattered diffraction (EBSD), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM). Uniform dispersion without damaging the CNTs structure is the key for the nanocomposite by powder metallurgy production process. The reinforcement effect occurs due to several strengthening mechanisms that act simultaneously. For the Al-CNT nanocomposites produced by ultrasonication as a dispersion/mixture technique, the observed improvement in the mechanical properties of nanocomposites can be attributed to the load transfer from the matrix to the CNTs. The strain hardening and the second-phase hardening can also have a small contribution to the strengthening of the nanocomposites.

Investigation of Mechanical Properties of Al/CNT Nanocomposites Produced by Powder Metallurgy

“…Al and nanocomposite samples were produced through a powder metallurgy route where the aluminum powder was dispersed/mixed to 1.00 vol.% of multi-walled carbon nanotubes. Both the aluminum powders from Goodfellow Cambridge Ltd. (Huntingdon, UK) and the carbon nanotubes from Fibermax Nanocomposites Ltd. (London, UK) were fully characterized with advanced techniques, such as SEM, TEM, HRTEM and RAMAN in previous works [12][13][14][15][16][17][18][19]. In these works, morphology and microstructure were studied to know the powders to a great extent and to evaluate the damage of the CNT during the nanocomposite production.…”

“…However, to avoid dubious results and indexing errors, the obtained data were submitted to a routine clean-up where the grain tolerance angle was determined to be 15 • and the need of 2 points minimum to define a grain. This cleaned data was used by the software of EBSD analysis TSL OIM Analysis 5.2 (EDAX Inc. (Ametek), Mahwah, NJ, USA) to perform the characterization through different EBSD results as described in previous works [16][17][18][19]. These EBSD maps also allowed the average grain size measurements using the grain maps combined by the Image J software (version 1.51, Wayne Rasban, National Institutes of Health, Bethesda MD, USA) to perform the measurement of 180-190 grains per sample.…”

Research progress on ceramic nanomaterials reinforced aluminum matrix nanocomposites

“…Maximum hardness and compressive strength of nanocomposite materials were observed with 8 wt% of carbon nanotube with 40 nm diameter, which was the highest diameter selected for the fabrication process. Multiwalled carbon nanotube reinforced aluminium matrix nanocomposites were described by Carneiro et al [67]. Nanocomposites were manufactured by powder metallurgy route via ultra-sonication and ball milling as dispersion/mixture techniques.…”

The Use of Carbon-Containing Compounds to Prepare Functional and Structural Composite Materials: A Review

“…At present, an effective method of consolidation is spark plasma sintering (SPS), the basic principle of which is to heat the powder material by passing a pulsed current with simultaneous application of pressure [126][127][128]. Another paper [129] provides a general view of the strengthening mechanisms of Al-CNT nanocomposites fabricated using 1 vol. % CNT using the powder metallurgy method using the ultrasonic treatment and its combination with a ball mill (Figure 7).…”

“…The second group includes the use of individual CNTs due to their high mechanical and electrical properties [84,130]. Another paper [129] provides a general view of the strengthening mechanisms of Al-CNT nanocomposites fabricated using 1 vol. % CNT using the powder metallurgy method using the ultrasonic treatment and its combination with a ball mill (Figure 7).…”