Effect of CNT Contents on the Microstructure and Properties of CNT/TiMg Composites

Abstract

Carbon nanotubes (CNTs), dispersed in absolute ethanol, were evenly mixed into Ti/MgH2 powders by wet milling. Then, we applied the vacuum hot-pressed sinteringmethod to the CNTs/TiMg composite materials. An optical microscope (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and a field emission scanning electron microscope (FESEM) were used for the microstructure observation and phase analysis of samples. The mechanical properties were measured via the micro-vickers hardness. The results show that the main phases in the composites were Ti, Mg and C. Meanwhile, a small amount of Ti-Mg solid solution phase was also found. The cross-section morphology of the composites shows that the melted magnesium fills the grain interface during extrusion and that the composites have a better compactness.The microstructures of the composites have been greatly refined as the CNT contents increased. The structure of the composites was further refined when 0.5 wt.% CNTs were added. The fracture surface is obviously a ductile fracture. The microhardness increases obviously with the CNT content increasing. When the content of the CNTs is 1.0 wt.%, the microhardness of the composites reaches 232 HV, which is 24% higher than that of the matrix.

Manufacturing Techniques for Mg-Based Metal Matrix Composite with Different Reinforcements

“…It is clear from Table 7 that multiwalled Carbon-nanotubes-reinforced AZ31 and AZ91 composite were hot extruded at a temperature of 400 • C and 450 • C, respectively, having extrusion ratios of 5:1 and 9:1, respectively [19,70]. The multiwalled Carbon-nanotubesreinforced Mg composite, on the other hand, was hot extruded at 350 • C with an extrusion ratio close to 25:1 [14,15,21,22].…”

“…A similar concept is also applicable when MMC is prepared through the PM route Figure 5. The development of magnesium metal matrix composites through the PM process and its mechanical properties evaluation has been conducted by many researchers in the last few decades [14][15][16][17][18]21]. Hence, there are multiple reasons to consider the powder metallurgy process as a better technique for processing of MMCs.…”

“…From Table 4, it is clear that mixing speed is indirectly proportional to the mixing time. In the case of Graphene-reinforced Mg composite mixing speed is kept at 40 RPM while the mixing time was 72 h [21]. In the case of Ni-coated Carbon-nanotubes-reinforced AZ31 composite mixing speed was kept at 1500 RPM and the mixing time was 2 h [78].…”

“…Compacting parameters are summarised in Table 5. From Table 5, it is evident that in the case of multiwalled Carbon-nanotubes-reinforced Mg composite, multiwalled Carbon nanotubes and Aluminium powder reinforced Mg composite, Ni-coated Carbon-nanotubesreinforced Mg composite and Ni-coated Carbon-nanotubes-reinforced AZ31 composite the height and the diameter of the compact is kept 40 mm and 35 mm, respectively [14,15,21,37]. Whereas, in the case of multiwalled Carbon-nanotubes-reinforced AZ91 composite the height and the diameter of the compact are kept at 120 mm and 6 mm, respectively [77,80].…”

“…MMCs have been well recognized for superior mechanical properties, better thermal properties and wear resistance in comparison to their unreinforced monolithic counterparts. Various MMCs have been prepared with unique properties for specific applications [14][15][16][17][18][19][20][21]. Al-based, composites can have the best application suitable mechanical properties, improved low density, better dimensional stability and damping properties.…”