Microstructure and microhardness of metal matrix composites with carbon nanotubes produced by severe plastic deformation

R.K. Khisamov1, K.S. Nazarov1, S.N. Sergeev1*, R.R. Kabirov1§, R.R. Mulyukov1, A.A. Nazarov1
1Institute for Metals Superplasticity Problems of Russian Academy of Sciences, 39, Khalturin Str., Ufa, 450001,Russia
SEM images of samples with CNT’s in central part in copper and aluminium.Research of microstructure, X-ray diffraction and microhardness metall-matrix composites reinforced with carbon nanotubes (CNT) obtained by severe plastic deformation were carried out. As starting materials for the preparation of composites multi-walled CNT and powders of copper and aluminium were used. Composites in the form of discs with a diameter of 10 mm and a thickness of 0.15 mm were obtained by means of high pressure torsion about 5 GPa . Copper-CNT and aluminium-CNT with them 4% and 2% weight content of CNT respectively were investigated. Studies using scanning electron microscopy showed that in the center and on the edge of the disk microstructure is different. In particular, in the center of the disc the pores and cracks were observed. CNT are located predominantly in the form of cloth large extent. With increasing distance from the center to the edge of the disk, pores and cracks were absent, CNT accumulation were observed in the form of clusters. Microstructure analysis of composites using methods of transmission electron microscopy and X-ray diffraction showed that the introduction and increase concentration of CNT in the matrix of metal leads to decrease of the mean grain size up to 50 nm. Evaluation of the dislocation density and microhardness testing showed that with increasing concentration of CNT their values are increased. In particular, microhardness value of composite Cu-4%CNT and Al-2%CNT is 1.5 times higher compared to the metal without CNT. Rotating moments of composites depending on rotation number in the process of high pressure torsion were measured. Measurements have shown that the value of rotating moment for the sample with CNT exceeds that value for the sample without CNT.
Accepted: 26 May 2015
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