Abstract
Abstract : Unreinforced Ti64 alloys have been utilized in several engineering applications due to their decent mechanical properties. These alloys possess certain limitations such as low elastic modulus that needs to be improved. The introduction of a reinforcement material appears to be an excellent approach to overcome these limitations. By taking the advantage of outstanding mechanical properties of multiwalled carbonnanotubes (MWCNTs) such as: high specific strength and weight together with high stiffness, efforts were made using three different dispersion techniques at varying compositions of MWCNTs to disperse MWCNTs into the matrices of Ti64 to enhance its properties. The as-received powders were characterized using SEM for morphological analysis, Raman Spectroscopy for structural integrity and XRD for phase identification. The powders were then mixed at varied compositions (0.5 wt%, 1.0 wt% and 1.5 wt% of MWCNTS) using dry mixing, wet or solution ball mixing and tubular mixing techniques. The solution ball mixing process was carried out using ethanol as the solvent. The ball-to-powder-ratio (BPR) and milling balls used for the three dispersion techniques are 5:1 and stainless-steel balls respectively. Consolidation of the admixed powders to yield the titanium matrix composites was carried out using spark plasma sintering (SPS) method. The sintering parameters used are 1000oC temperature, heating rate of 50oC/min and 5minutes holding time. A combination of numerous analytical techniques was used to investigate the interfacial reactions and structural integrity of MWCNTs in the admixed powders and composites. This includes Scanning Electron Microscopy (SEM) equipped with Energy- Dispersive X-ray analysis (EDX), Raman Spectroscopy (RS) and X-ray Diffraction (XRD). The mechanical properties of the composites were determined using the Vickers hardness tests. Microstructural characterization of the dry mixing samples depicted relative dispersion of MWCNTs in Ti64 when compared to other methods. Also, the highest hardness value was observed in the dry mixing sintered samples. On the hand, the Raman spectra of the three dispersion methods indicated slight formation of TiC intermetallic compound. Holistically, the dry mixing techniques tends to offer better dispersion and mechanical properties when compared to other methods.
M.Sc. (Metallurgy)