EBSD Analysis of Metal Matrix Nanocomposite Microstructure Produced by Powder Metallurgy

Íris Carneiro,Filomena Viana,Manuel F Vieira,Sónia Simões,José V Fernandes

doi:10.3390/nano9060878

Abstract

The development of metal nanocomposites reinforced by carbon nanotubes (CNTs) remains a focus of the scientific community due to the growing need to produce lightweight advanced materials with unique mechanical properties. However, for the successful production of these nanocomposites, there is a need to consolidate knowledge about how reinforcement influences the matrix microstructure and which are the strengthening mechanisms promoting the best properties. In this context, this investigation focuses on the study of the reinforcement effect on the microstructure of an Ni-CNT nanocomposites produced by powder metallurgy. The microstructural evolution was analysed by electron backscattered diffraction (EBSD). The EBSD results revealed that the dispersion/mixing and pressing processes induce plastic deformation in the as-received powders. The dislocation structures produced in those initial steps are partially eliminated in the sintering process due to the activation of recovery and recrystallization mechanisms. However, the presence of CNTs in the matrix has a significant effect on the dislocation annihilation, thus reducing the recovery of the dislocation structures.

Highlights

The growing interest in the development of metallic matrix nanocomposites (MMNCs) is attributed to the extraordinary mechanical, physical and chemical properties that can be obtained by combining different types of materials
The effect of carbon nanotubes (CNTs) on the microstructure of the Ni-CNT nanocomposites produced by powder metallurgy was evaluated
After the initial dispersion/mixing and pressing processes, the microstructure of the samples with and without CNTs is similar. Both samples are characterized by an increase in the low-angle boundaries fraction and grain misorientation that are related to the plastic deformation that occurs in these steps

Summary

Introduction

The growing interest in the development of metallic matrix nanocomposites (MMNCs) is attributed to the extraordinary mechanical, physical and chemical properties that can be obtained by combining different types of materials. This development depends on several factors, since the improvement in the mechanical properties of the metallic matrices is strongly related, to the composition of the reinforcement material used, and to its size, morphology, volume fraction, interfacial bonding to the matrix and the uniformity of its dispersion in the metal matrix [1,2]. Strain hardening (the increase in dislocation density) has been identified as an important strengthening mechanism of MMNCs [34,35]

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