Search

WC powders with an average crystallite size of 10 nm were successfully prepared by ball milling of micron-sized tungsten carbide powders. Grain growth inhibitors (VC and Cr3C2) with concentrations of 0.6 wt% each were added to nanocomposites of WC–9Co and WC–12Co, in both as-received and milled WC. Powder mixtures were then consolidated using spark plasma sintering technique at 1200 and 1300 °C for 10 min under high vacuum and pressure of 50 MPa. The influence of WC crystallite size, Co content, and sintering temperature over microstructure and mechanical properties of the resulting composites were studied through XRD and FESEM. Densification and attained grain sizes of the sintered products were measured by Archimedes principle and Scherrer procedure, respectively. Moreover, microhardness (Hv30) and fracture toughness were measured and compared for each composition to comparatively assess the individual effect. It was observed that the addition of VC and Cr3C2resulted in decreased densification of the synthesized composites. These grain growth inhibitors were found to limit grain sizes to 131 nm with an average hardness of 1592 Hv30and fracture toughness of 9.23 Mpam1/2. [ABSTRACT FROM PUBLISHER]

Al based alloys reinforced with different amounts (5, 12 and 20 wt-%) of nanosized SiC particulates were synthesised by mechanical alloying and consolidated by the spark plasma sintering (SPS) technique. The distribution of the reinforcement phase in the composite was evaluated as a function of the milling time and the amount of SiC. The processed materials were characterised by scanning electron microscopy and energy dispersive spectroscopy for the morphology and composition and X-ray diffraction. Continuous reduction in crystallite size was observed as milling progressed and after milling for 20 h the resulting powders reached a grain size of <100 nm. These Al-SiC composites were successfully consolidated by the SPS method at different sintering temperatures of 400, 450 and 500°C. It is suggested that a higher hardness can be achieved even at 20 wt-%SiC when a higher sintering temperature, for example, above 500°C, is used. [ABSTRACT FROM AUTHOR]

Three aluminium metal matrix composites containing reinforcing particles of B4C, SiC and Al2O3 (0–20 vol.%) were processed. The stir-casting manufacturing route followed by hot extrusion was utilized, being one of the cost-effective industrial methods. A clear interfacial reaction product/layer was found at Al–SiC interface for composites held for a relatively long processing time (>30 min). No reaction product was observed at Al–B4C and Al–Al2O3 interfaces at the resolution limit of the SEM used. On the other hand, two secondary phases (alumina and another phase containing aluminium, boron and carbon) were found in the aluminum matrix away from the interface in Al–B4C composites. From the fracture surface analysis, B4C reinforced Al composite seemed to exhibit a better interfacial bonding compared to the other two composites. [Copyright &y& Elsevier]