Papers by Keyword: Metal Matrix Nanocomposite

Abstract: Recent researches in the domain of casting confirmed that the mechanical properties of aluminum and magnesium based nanocomposites can be appreciably enhanced when ultrasonic cavitation assisted solidification processing is used. Ultrasonic cavitation assisted solidification processing is used for the manufacturing of aluminum and magnesium alloy based metal matrix nanocomposites reinforced with nanoceramic particles. In this solidification processing, formation of clusters have been minimized and the nanoreinforcements were distributed uniformly in aluminum and magnesium matrix nanocomposites. The ultrasonic assisted casting approach will manage the grain dimensions via minimizing agglomeration of nanoparticles in metal matrices. This paper opinions the properties and morphology of aluminum and magnesium based metal matrix nanocomposites fabricated through ultrasonic assisted casting process.

Abstract: The paper introduces a new method to produce large sized Al-B₄C-Al₂O_3np composites, which combines ball milling to prepare Al₂O_3np/Al mixed powder and semi-solid casting to contribute the injection of Al₂O_3np/Al mixed powder into the melt. The deformation performance of Al₂O_3np and micro-Al through ball milling with different Al/Al₂O_3np ratios, different milling time and different balls were studied respectively. It was revealed that micro-Al particles were milled from twisted and crimpled foil pieces to shuttles with Al₂O_3np embedded on it through 4h milling with 10mm balls. And we consider it as the best bonding between Al₂O_3np and micro-Al we could attain. And a plate of 25kg of Al-B₄C-Al₂O_3np composite was fabricated successfully with the injection of the Al₂O_3np/Al mixed powder. Spherical Al₂O_3np of 300nm and needle-like TiB₂ with 200nm in radius and 800nm-4μm in length were found in SEM photographs. Tensile properties of Al-B₄C-Al₂O_3np composites were tested at room temperature and high temperature. It was showed higher mechanical properties than Al-B₄C composites at room temperature and elevated temperature. Particularly, a 40% increase of UTS of Al-15wt.% B₄C-1wt.%Al₂O_3np at 350°C was observed.

Abstract: Ever since copious nucleation was shown to be an efficient, cost effective method for producing semi-solid slurry, many processes have been developed to take advantage of the cost savings inherent in this method of slurry production. Despite great advances in various aspects of semi-solid processing, the cost competitive nature of the industry, most noticeably the auto industry, has prevented a wider adoption of semi-solid casting technology. This research aims to realize a more industrial appealing process by combining the synergistic benefits of semi-solid casting technology with metal matrix nanocomposite (MMNC) technology, thus creating higher value products with superior properties cost-effectively. To do this, a process that produces a semi-solid slurry though the nucleation catalysis induced by nanoparticle additions as small as 1 wt. % to alloys is proposed and the results are presented in this paper. Examination of the potential for nano-scale inoculants to catalyze nucleation of solidification showed that despite their small sizes, inoculants on the scale of tens of nanometers are capable of catalyzing nucleation in the zinc and aluminum alloys studied. Employing the differential scanning calorimetry (DSC), differential thermal analysis (DTA), and droplet emulsion techniques with nanocomposite samples showed a significant reduction in undercooling owing to the homogeneous distribution of nanoparticles by ultrasonic mixing and the potency of those nanoparticles to catalyze nucleation. Comparison of undercoolings between different types of nanoparticles, such as silicon carbide (SiC), gamma and alpha alumina (Al2O3), and titanium carbide (TiC), to relative potencies predicted by minimum lattice disregistry showed a strong correlation. Results were also examined in light of free growth and nucleation controlled grain initiation. For nanoparticles predicted to be potent nucleation catalysts by lattice disregistry, the undercoolings observed fell into the free growth controlled grain initiation regime.

Abstract: In this research work, a high-energy ball mill has been applied to prepare an Al/SiC nanocomposite. The formation mechanism of the nanocomposite was investigated. This nanocomposite contained the nanocrystalline characteristics. Crystallite size, lattice strain and particle size of the nanocomposite as a function of milling time were determined. SEM micrographs showed that the nanocomposite powders agglomerated after milling. The particle size analysis confirmed the agglomeration of the nanocomposite particles. TEM observations showed that the SiC particles were in the nanometer size and these particles embedded in the Al matrix, and the nanocomposite produced in the final stage of mechanical alloying. In addition, a simple model checked for the refinement of the crystallite and the particle size of nanocomposite.

Abstract: Carbon nanotubes (CNTs) have been the subject of intensive study for applications in the fields of nanotechnologies in recent years due to their superior mechanical, electric, optical and electronic properties. Because of their exceptionally small diameters (≈ several nm) as well as their high Young’s modulus (≈ 1 TPa), tensile strength (≈ 200 GPa) and high elongation (10-30%) in addition to a high chemical stability, CNTs are attractive reinforcement materials for light weight and high strength metal matrix composites. In this study, bottom-up type powder processing and top-down type SPD (severe plastic deformation) approaches were combined in order to achieve full density of CNT/metal matrix composites with superior mechanical properties by improved particle bonding and least grain growth, which were considered as a bottle neck of the bottom-up method using the conventional powder metallurgy of compaction and sintering. ECAP (equal channel angular pressing), the most promising method in SPD, was used for the CNT/Cu powder consolidation. The powder ECAP processing with 1, 2, 4 and 8 route C passes was conducted at room temperature. It was found by mechanical testing of the consolidated CNT/Cu that high mechanical strength could be achieved effectively as a result of the Cu matrix strengthening and improved particle bonding during ECAP. The ECAP processing of powders is a viable method to achieve fully density CNT-Cu nanocomposites.

Abstract: In this study, powder processing and severe plastic deformation (SPD) approaches were combined in order to achieve both full density and good particle-matrix bonding in CNT and Cu powder mixtures without grain growth, which was considered as a bottle neck of the bottom-up method in the conventional powder metallurgy of compaction and sintering. Equal channel angular pressing (ECAP), one of the most promising methods in SPD, was used for the powder consolidation. The powder ECAP processing with 1, 2, 4 and 8 passes was conducted at room temperature. It was found by microhardness tests and microstructure characterization that relatively high mechanical strength could be effectively achieved as a result of the well bonded powder contact surface during powder ECAP. The SPD processing of powders is a viable method to achieve both fully density and good particle bonding in CNT-metal matrix nanocomposites.