Papers by Keyword: Metal Matrix Composite (MMC)

Abstract: The powder metallurgy technique was adopted to prepare SiCp copper alloy matrix composites. The mechanical properties of the composites were measured to investigate the influence of processing parameters, SiC particle characteristics and metallic coating (copper) of the SiC particles. It was found that the mechanical properties of the composites prepared by pressing, sintering, re-pressing, and resintering are superior to those of composites prepared by the pressing and sintering route, and that sintering temperature was an important factor in controlling composite properties. Changes in hardness, theoretical density, ultimate tensile strength, and wear resistance of composites containing SiC of varying silicon carbide content were observed. In all cases, composites made from copper coated SiCp exhibited better properties than those from uncoated particles.

Abstract: Consolidation of aluminium alloys by sintering present a main problem: the oxide layer that cover aluminium particles. Some alternatives are studied in this work as solution to the oxide layer problem during the sintering of series 2xxx aluminium alloys. One of these solutions is related to the addition of tin traces, and the other is the addition of a second alloy. Moreover, aluminium metal matrix composites are characterized by excellent properties as combination of properties which comes from the matrix and from the reinforcement. In the first part of this work is analyzed the influence of trace additions, and the last part of this study is focused to the analysis of one aluminium matrix composite as the influence of several quantities of reinforcement.

Abstract: It is favorable to disperse fine strengthening particles under 1μm to expect the effective dispersion strengthening mechanism of metal matrix composites. In this research, TiB2 particle was synthesized in Al matrix by a combustion reaction and the influence of the powder blending ratio was examined in detail. The mole mixture ratio of Ti and B powder was fixed to B/Ti=2, and the blending ratio of Al powder was varied from 40 to 70vol%. The compacted blended powder was heated under an Ar atmosphere in an induction furnace, and heating was stopped immediately after the combustion reaction took place. The synthesized TiB2 particle became finer by increasing the blending ratio of Al, and the dispersion of particles about 0.3μm was achieved. However, large quantity of Al-Ti intermetallic compounds remained when 70vol% Al was blended, indicating that the combustion reaction was not completed in this specimen.

Abstract: A method for measuring the stress and strain distribution in the composite materials and residual stress at the interface in the fiber reinforced composite has been developed. The strains are measured using an electron Moiré method and then the stresses are calculated from these strains. A very fine model grid with frequencies up to 10,000lines/mm can be fabricated using the optical and electron lithography techniques on the surface of the specimen and an electron beam scan which spaces are almost same as that of model grid the can be used for master-grid. The difference of the amount of secondary electrons per a primary electron makes Moiré fringes that consists bright and dark parts. Micro-creep deformation and residual strain and stress near the fibers of composite materials were measured by this method.

Abstract: Aluminum alloys were reinforced with AlN particles using a novel chemical in situ technique. Thermodynamic analyses were made to identify the conditions for the in situ formation of the AlN in Al alloys. Experiments were conducted in the temperature range of 1173-1473 K by injecting ammonia gas. The composites with AlN quantity varying from 5 to 51 wt % were produced. Effect of process variables such as gas injection time, flow rate of ammonia gas and temperature of the alloy melt on the formation of AlN was studied. Increase in either injection time or flow rate of the ammonia gas increased the nitride content. AlN particles with an average size of 500 nm were produced. The measured Vickers hardness of the composites formed increased with increasing AlN content. The amount of AlN experimentally formed is in good agreement with the thermodynamically predicted data.

Abstract: Metal matrix composites (MMCs) have been found to possess tremendous prospective engineering applications that require materials offering a combination of lightweight with considerably enhanced mechanical and physical properties. However, the applications of MMCs are limited by their poor machinability which is a result of their highly abrasive nature that causes excessive wear to the cutting tools. In this study, an investigation into the mechanism of the tool wear in cutting of MMCs is carried out. It is found that during cutting of an MMC, the tool cutting edge will impact on the reinforcement particles. The impacted particles will then either be dislodged from the matrix, doing no harm to the tool, or be embedded into the matrix, ploughing on the tool flank and causing excessive tool flank wear. According to this tool wear mechanism, a pressured steam jet approach is developed for the minimization of the tool wear by preventing the impacted reinforcement particles from being embedded in the workpiece matrix. Experimental tests for cutting of SiC–aluminum MMC using cubic boron nitride (KB-90) and polycrystalline diamond (KP-300) tool inserts with the aid of the pressured steam jet are conducted. The results show that from full factorial design of experiments the effect of the pressured steam jet plays a significant role on the tool wear followed by tool inserts and depth of cut. The working mechanism of the pressured steam jet method and the experimental testing results are discussed in detail.

Abstract: This study deals with the processing, microstructure and properties of the carbide reinforced copper matrix composites. Powder technology was used to successfully fabricate the composites. NbC particulates were used as reinforcements for copper matrix. The microstructure of the composite was characterized by scanning electron microscopy. The microstructural study revealed that the NbC particles were distributed uniformly in the matrix phase. No interface debonding and micro- cracks were observed in the composite. NbC particles were found in round shape in copper matrix composite. The composite hardness of 78 HRA was found with 60vol% NbC content. Electrical conductivity as high as 7%IACS was achieved. The wear performance and conductivity value predicts that NbC reinforced copper matrix composites can be used as sliding contact applications.

Abstract: The Uranium Extraction (UREX) family of processes uses solvent extraction techniques designed to partition spent uranium and transuranic (TRU) isotopes from fission product waste. Once separated, the collective TRU elements (Np, Pu, Am, and Cm) can be recycled in advanced nuclear energy systems. A zirconium matrix cermet is proposed as a fuel form for this application. Processing methods have been designed to convert the TRU product and spent Zircaloy cladding into feed materials for the hot extrusion of the cermet fuel pins. The TRU conversion process is being developed using a surrogate mixture of uranium and cerium nitrate solutions to generate mixed oxide microspheres. The Zircaloy recovery process is a hydride-dehydride method that is being demonstrated at the bench scale. The powder products from these methods may be combined through hot extrusion into a cermet composite; demonstration experiments using zirconium powder and zirconia microspheres have been completed.

Abstract: It is attractive to use multi-wall carbon nanotubes (MWNTs), which has a high modulus and strength, to enhance the properties of metal matrix composites by hybrid strategy. In this paper, novel aluminum borate whisker (ABOw) and MWNTs hybrid composites were prepared by squeeze cast technique and the properties were investigated. The results show that hybrid preforms may be made by co-deposition of ABOw and MWNTs in a solution by wet method. MWNTs separate the ABOw from whisker-to-whisker contact and decrease the compressive deformation of the hybrid preforms during squeeze cast processing. MWNTs distribute along mainly in the grains of aluminum matrix, making the mechanical properties of the hybrid composites higher than singularly reinforced composite.

Abstract: One kind of 3DNMMC with different volume fraction reinforcement phase was fabricated by pressureless technique. The bending strength and fracture toughness were tested by 3-P bending strength experiments. When the volume fraction of reinforcement phase phase was not in excess of 10%, composites had an improvement of bending strength and fracture toughness owing to relatively homogeneous Al2O3 particle distribution encircled by metal matrix and the occurrence of interface reaction product as MgAlO2 spinel phase. Much and smaller craters and dimples are observed in metal matrix alloy and limited ductility of composites causes the early failure of composites. With the increases of volume fraction of reinforcement phase phase, crack characteristic consist of crack nucleation, growth, coalescence and crack propagation became the main fracture failure mechanisms.