Investigation on the Strengthening Mechanisms of Nickel Matrix Nanocomposites.

Íris Carneiro,José Valdemar Fernandes,Sónia Simões

doi:10.3390/nano11061426

Abstract

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.

Highlights

Nowadays, there is a great interest in developing more sustainable mobility, which can be achieved by reducing fuel consumption and, emissions from the transport industry
The nanocomposites produced by ultrasonication as dispersion/mixture process showed a greater increase in hardness than the sample produced under the same conditions without the reinforcement
For nanocomposites produced through carbon nanotubes (CNTs) untangle by ultrasonication and dispersion/mixture by ball milling, the increase in the hardness is only observed for the nanocomposites produced by ball milling with a time of more than

Summary

Introduction

There is a great interest in developing more sustainable mobility, which can be achieved by reducing fuel consumption and, emissions from the transport industry. In this sense, the scientific community has been dedicated to studying and developing high-performance lightweight alloys to produce structural components. Different types of materials are used as reinforcement metal matrix composites, such as ceramic, intermetallic, carbides, and carbon-based nanomaterials. These reinforcements can be used at the nanoscale, which has shown greater efficiency in reinforcing metals instead of micrometric reinforcements. Within this range of nano-sized reinforcements, carbon-based nanoparticles, such as carbon nanotubes (CNTs), have been the focus of intense interest in producing MMNCs [6,7,8,9,10,11,12,13,14,15,16]

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