Nanomechanical properties of spark plasma sintered multiwall carbon nanotubes reinforced Ti6Al4V nanocomposites via nanoindentation technique A.M. Okoro a,⇑ , S.S. Lephuthing a , M.A. Awotunde a , O.E. Falodun a , R. Machaka b , P.A. Olubambi a a Centre for Nanoengineering and Tribocorrosion, Department of Metallurgy, School of Mining, Metallurgy and Chemical Engineering, University of Johannesburg, South Africa b Council for Scientific and Industrial Research, Pretoria, South Africa article info Article history: Received 15 September 2019 Received in revised form 5 November 2019 Accepted 26 December 2019 Available online xxxx Keywords: Nanomechanical properties Nanoindentation Titanium alloy Multiwall carbon nanotubes Spark plasma sintering abstract In this study, nanoindentation tests were carried out to investigate the nanomechanical behaviours of Ti6Al4V and its nanocomposites comprising of multiwall carbon nanotubes (MWCNTs) fabricated via spark plasma sintering. Prior to the nanoindentation tests, the fabricated alloy and the nanocomposites comprising of 0.5 and 1.0 wt% of MWCNTs were observed under a scanning electron microscope (SEM) to reveal the morphology and the presence of the MWCNTs in the nanocomposites. The nanoindentation study was conducted using a Berkovich diamond indenter with a load of 75 mN to ascertain the nanohardness, reduced elastic modulus, plasticity index and elastic recovery index of the sintered mate- rials. The SEM results revealed the dispersibility of the nanotubes in the titanium-based matrix and the presence of lamellar structures in the fabricated alloy. Furthermore, it was observed that the nanohard- ness and elastic modulus of the sintered materials ranges from 3.4–5.7 GPa and 27.6–38.9 GPa, which improved with the MWCNTs content. Also, the elastic recovery index increased with MWCNTs content in the nanocomposites. While the sintered Ti6Al4V displayed the maximum plasticity during the nanoin- dentation study. Ó 2020 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the scientific committee of the 2nd International Conference on Recent Advances in Materials & Manufacturing Technologies. 1. Introduction Recent progress in materials science has unveiled the possibili- ties of assessing the mechanical behaviours of various materials at a micro and nanoscale range. These possibilities have been actual- ized by the application of an innovative mechanical testing tech- nique called nanoindentation. Although, nanoindentation technique has been in existence since the mid-1970s for the testing of a small volume of materials [1]. However, the research breakthrough by Oliver and Pharr method [2] using the Berkovich nanoindenter in investigating the hardness and elastic modulus of six distinct materials have given the technique unprecedented attention in recent years. This mechanical testing method has been successfully employed to explore the mechanical behaviours of a wide range of materials namely ceramics, composites, alloys, coated surfaces, and thin- film to mention but a few [3]. The widespread applications of this technique are traceable to its effectiveness, and its capability to probe small materials without hampering with their microstruc- tures [4]. Additionally, it can probe the grains and grain boundaries by assessing the mechanical properties of those regions of the materials. In the past years, different research adventures have been car- ried out using destructive testing techniques to assess the mechan- ical properties such as tensile, hardness and fracture toughness of a wide range of materials. However, it usually leads to the destruc- tion of the microstructure without actualizing results of higher accuracy. Hence, in a bid to understand the effects of multiwall carbon nanotubes (MWCNTs) addition on the nanomechanical properties of Ti6Al4V matrix without hampering the microstructure of the https://doi.org/10.1016/j.matpr.2019.12.285 2214-7853/Ó 2020 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the scientific committee of the 2nd International Conference on Recent Advances in Materials & Manufacturing Technologies. ⇑ Corresponding author. E-mail address: okoromo@gmail.com (A.M. Okoro). Materials Today: Proceedings xxx (xxxx) xxx Contents lists available at ScienceDirect Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr Please cite this article as: A. M. Okoro, S. S. Lephuthing, M. A. Awotunde et al., Nanomechanical properties of spark plasma sintered multiwall carbon nan- otubes reinforced Ti6Al4V nanocomposites via nanoindentation technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.285