Abstract
Innovations in materials development has engendered the improvement of the properties of titanium alloys for diverse engineering applications. In this study, titanium alloy (Ti6Al4V) and multiwall carbon nanotubes (MWCNT) were mixed using shift-speed ball milling (SSBM) technique to achieve the uniform dispersion of MWCNT in the Ti6Al4V matrix. The starting and admixed powders were characterized using scanning electron microscopy equipped Energy dispersive X-Ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), Raman spectroscopy and Transmission electron microscopy (TEM). Detailed TEM characterization was carried out to reveal the structural evolutions of the MWCNT during the dispersion process using selected area diffraction and fast Fourier transform pattern. The admixed powders were then consolidated using the spark plasma sintering machine (model HHPD-25, FCT GmbH Germany). Furthermore, various characterization technique such as XRD, SEM-EDS, optical microscopy (OM) was employed to understand the phase evolutions, morphology, microstructural changes and fractography of the fabricated nanocomposites. The mechanical properties of the fabricated materials were further investigated using the Vickers microhardness tester (FALCON 500 series) and the nanoindentation technique (ultra nanoindenter) UNHT. The study resulted in five (5) research articles, each article investigated the following respectively; (1) the previous works that have been conducted in SPS of titanium-based nanocomposites reinforced with MWCNT, (2) the dispersibility, structural evolutions and interfacial bonding of MWCNT in Ti6Al4V powders using the SSBM technique, (3) the evaluation of the influence of varying sintering temperature on the sintering and densification behaviours and microhardness of the fabricated alloy and nanocomposites, (4) the effects of MWCNT addition on the change in microstructures and mechanical properties of the fabricated nanocomposites, and (5) the influence of MWCNT on the nanomechanical properties of the fabricated nanocomposites. During the dispersion process, the Raman and XRD pattern of the admixed powders showed that mechanical stresses were induced on the walls of the nanotubes which does not result in defects on the MWCNT. Optimal dispersion of MWCNT was achieved on the nanocomposite grades comprising of 0.5 and 1.0 wt.% nanotubes. Additionally, the dispersibility decreased with the increase in concentration of the MWCNT in the Ti6Al4V matrix. Meanwhile, the nanocomposite grades with higher fraction of MWCNT experienced higher deformation of the nanotubes during the dispersion process. The optimal dispersion of MWCNT in Ti6Al4V matrix with minimal...
D.Ing. (Metallurgy)