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

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1711
Author(s):  
Íris Carneiro ◽  
José Valdemar Fernandes ◽  
Sónia Simões
Keyword(s):  
Powder Metallurgy ◽  
Aluminum Matrix ◽  
Microstructural Characterization ◽  
Second Phase ◽  
Small Contribution ◽  
Strengthening Mechanisms ◽  
Electron Backscattered Diffraction ◽  
Phase Hardening ◽  
Uniform Dispersion ◽  
Matrix Nanocomposites

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.

scholarly journals Investigation on the Strengthening Mechanisms of Nickel Matrix Nanocomposites

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1426
Author(s):  
Íris Carneiro ◽  
José Valdemar Fernandes ◽  
Sónia Simões
Keyword(s):  
Grain Refinement ◽  
Metal Matrix ◽  
Load Transfer ◽  
Second Phase ◽  
Strengthening Effect ◽  
Small Contribution ◽  
Strengthening Mechanisms ◽  
Metal Matrix Nanocomposites ◽  
The Matrix ◽  
Matrix Nanocomposites

The strengthening effect of carbon nanotubes (CNTs) in metal matrix nanocomposites occurs due to several mechanisms that act simultaneously. The possible strengthening mechanisms for metal matrix nanocomposites reinforced with CNTs consist of: (1) load transfer, (2) grain refinement and texture strengthening, (3) second phase strengthening, and (4) strain hardening. The main focus of this work is to identify the strengthening mechanisms that play a role in the case of the Ni-CNT nanocomposite produced by powder metallurgy. For the dispersion and mixing of the metallic powders with CNTs, two different routes were performed by ultrasonication and ball milling. The results indicated that four different strengthening mechanisms are present in the nanocomposites and had a different contribution to the final mechanical properties. The load transfer and the increase in dislocation density seem to strongly affect the properties and microstructure of the nanocomposite. The grain refinement and the presence of second phase particles have a small contribution in the strengthening of this nanocomposite, since the introduction of CNTs in the Ni matrix slightly affects the size and orientation of the grains in the matrix and a few nanometric particles of Ni3C were identified.

Microstructural characterization of a rapidly solidified Al-Fe-V-Si alloy for elevated temperature applications

1988 ◽  
Vol 46 ◽  
pp. 550-551
Author(s):  
R. E. Franck ◽  
J. A. Hawk ◽  
G. J. Shiflet
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Grain Growth ◽  
Volume Fraction ◽  
Microstructural Characterization ◽  
Second Phase ◽  
Microstructural Stability ◽  
Elevated Temperature Strength ◽  
Temperature Applications

Rapid solidification processing (RSP) is one method of producing high strength aluminum alloys for elevated temperature applications. Allied-Signal, Inc. has produced an Al-12.4 Fe-1.2 V-2.3 Si (composition in wt pct) alloy which possesses good microstructural stability up to 425°C. This alloy contains a high volume fraction (37 v/o) of fine nearly spherical, α-Al12(Fe, V)3Si dispersoids. The improved elevated temperature strength and stability of this alloy is due to the slower dispersoid coarsening rate of the silicide particles. Additionally, the high v/o of second phase particles should inhibit recrystallization and grain growth, and thus reduce any loss in strength due to long term, high temperature annealing.The focus of this research is to investigate microstructural changes induced by long term, high temperature static annealing heat-treatments. Annealing treatments for up to 1000 hours were carried out on this alloy at 500°C, 550°C and 600°C. Particle coarsening and/or recrystallization and grain growth would be accelerated in these temperature regimes.

A Comparison of Tem and Apfim to the Interpretation of Modulated Microstructures

1985 ◽  
Vol 43 ◽  
pp. 70-71
Author(s):  
M.G. Burke ◽  
M.K. Miller
Keyword(s):  
Low Temperature ◽  
Microstructural Characterization ◽  
Superlattice Reflection ◽  
High Volume ◽  
Atom Probe ◽  
Dark Field ◽  
Miscibility Gap ◽  
Second Phase ◽  
Two Phase ◽  
Probe Field

Interpretation of fine-scale microstructures containing high volume fractions of second phase is complex. In particular, microstructures developed through decomposition within low temperature miscibility gaps may be extremely fine. This paper compares the morphological interpretations of such complex microstructures by the high-resolution techniques of TEM and atom probe field-ion microscopy (APFIM).The Fe-25 at% Be alloy selected for this study was aged within the low temperature miscibility gap to form a <100> aligned two-phase microstructure. This triaxially modulated microstructure is composed of an Fe-rich ferrite phase and a B2-ordered Be-enriched phase. The microstructural characterization through conventional bright-field TEM is inadequate because of the many contributions to image contrast. The ordering reaction which accompanies spinodal decomposition in this alloy permits simplification of the image by the use of the centered dark field technique to image just one phase. A CDF image formed with a B2 superlattice reflection is shown in fig. 1. In this CDF micrograph, the the B2-ordered Be-enriched phase appears as bright regions in the darkly-imaging ferrite. By examining the specimen in a [001] orientation, the <100> nature of the modulations is evident.

scholarly journals Wettability in Metal Matrix Composites

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1034
Author(s):  
Massoud Malaki ◽  
Alireza Fadaei Tehrani ◽  
Behzad Niroumand ◽  
Manoj Gupta
Keyword(s):  
Metal Matrix Composites ◽  
Metal Matrix ◽  
Aluminum Matrix ◽  
Interfacial Strength ◽  
High Strength ◽  
Aluminum Matrix Composites ◽  
Matrix Composites ◽  
Metal Matrix Nanocomposites ◽  
Aerospace Applications ◽  
Matrix Nanocomposites

Metal matrix composites (MMCs) have been developed in response to the enormous demand for special industrial materials and structures for automotive and aerospace applications, wherein both high-strength and light weight are simultaneously required. The most common, inexpensive route to fabricate MMCs or metal matrix nanocomposites (MMNCs) is based on casting, wherein reinforcements like nanoceramics, -carbides, -nitrides, elements or carbon allotropes are added to molten metal matrices; however, most of the mentioned reinforcements, especially those with nanosized reinforcing particles, have usually poor wettability with serious drawbacks like particle agglomerations and therefore diminished mechanical strength is almost always expected. Many research efforts have been made to enhance the affinity between the mating surfaces. The aim in this paper is to critically review and comprehensively discuss those approaches/routes commonly employed to boost wetting conditions at reinforcement-matrix interfaces. Particular attention is paid to aluminum matrix composites owing to the interest in lightweight materials and the need to enhance the mechanical properties like strength, wear, or creep resistance. It is believed that effective treatment(s) may enormously affect the wetting and interfacial strength.

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