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1
Coleman, Sarah L. "The corrosion of metal matrix composites." Thesis, University of Bath, 1991. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303434.
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2
Williams, J. R. "Corrosion of aluminium-copper-magnesium metal matrix composites." Thesis, University of Nottingham, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239852.
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3
Furness, Justin Albert George. "Thermal cycling creep of aluminium based composites." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239618.
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4
Kang, Hyung-gu. "Locally reinforced squeeze cast aluminium alloy metal matrix composites." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294391.
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5
Perrin, Carl. "Wear of aluminium alloys and alluminium-based MMCs." Thesis, University of Sheffield, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294216.
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6
Whitehouse, Anne Frances. "Damage and failure of discontinuously reinforced aluminium composites during tensile deformation." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319543.
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7
Askew, John Russell. "Transient liquid phase bonding of Aluminium-based MMCs." Thesis, Brunel University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324651.
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8
Dibelka, Jessica Anne. "Mechanics of Hybrid Metal Matrix Composites." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/50579.
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The appeal of hybrid composites is the ability to create materials with properties which normally do not coexist such as high specific strength, stiffness, and toughness. One possible application for hybrid composites is as backplate materials in layered armor. Fiber reinforced composites have been used as backplate materials due to their potential to absorb more energy than monolithic materials at similar to lower weights through microfragmentation of the fiber, matrix, and fiber-matrix interface. Composite backplates are traditionally constructed from graphite or glass fiber reinforced epoxy composites. However, continuous alumina fiber-reinforced aluminum metal matrix composites (MMCs) have superior specific transverse and specific shear properties than epoxy composites. Unlike the epoxy composites, MMCs have the ability to absorb additional energy through plastic deformation of the metal matrix. Although, these enhanced properties may make continuous alumina reinforced MMCs advantageous for use as backplate materials, they still exhibit a low failure strain and therefore have low toughness. One possible solution to improve their energy absorption capabilities while maintaining the high specific stiffness and strength properties of continuous reinforced MMCs is through hybridization. To increase the strain to failure and energy absorption capability of a continuous alumina reinforced Nextel" MMC, it is laminated with a high failure strain Saffil® discontinuous alumina fiber layer. Uniaxial tensile testing of hybrid composites with varying Nextel" to Saffil® reinforcement ratios resulted in composites with non-catastrophic tensile failures and an increased strain to failure than the single reinforcement Nextel" MMC. The tensile behavior of six hybrid continuous and discontinuous alumina fiber reinforced MMCs are reported, as well as a description of the mechanics behind their unique behavior. Additionally, a study on the effects of fiber damage induced during processing is performed to obtain accurate as-processed fiber properties and improve single reinforced laminate strength predictions. A stochastic damage evolution model is used to predict failure of the continuous Nextel" fabric composite which is then applied to a finite element model to predict the progressive failure of two of the hybrid laminates.Ph. D.
9
Abdullah, Abu. "Machining of aluminium based Metal Matrix Composite (MMC)." Thesis, University of Warwick, 1996. http://wrap.warwick.ac.uk/34661/.
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The machining of aluminium 2618 particulate reinforced Metal Matrix Composite (MMC) with 18 vol. % silicon carbide (SiC) using cemented carbide cutting tools has been undertaken. Two grades of cemented carbide inserts, uncoated K68 grade and coated KC910 grade (coated with TiC and A1203) having negative and positive rake angles (with and without chip breaker) have been used to machine this material in order to understand the machining process, tool failure modes and wear mechanisms. Turning tests in the speed range 15 - 10 m/min have been carried out at 0.2,0.4 and 0.6 mm/rev feed rates and 2 mm and 4 mm depths of cut. Both cemented carbide tools have been shown to be capable of machining the MMC and give reasonable tool lives. Low speed and high feed rate are found to be a good combination in order to machine this material effectively. Coated KC910 grade inserts with negative rake angle gave the best performance. The use of a chip breaker has no significant effect on the machining process of the NMC because the material is one which inherently short chips due to ductility limitations caused by the particles. Tool failure mode studies showed that the tools failed by flank wear. Tool wear mechanism analysis indicated that abrasion wear was the tool life controlling factor under all cutting conditions. The tool wear is related to the direct contact between the abrasive hard SiC particles and the cutting edge and their relative motion to the rake and clearance face. Hence, the hardness of the SiC particles is a dominant factor for the tool wear. Two separatem odels of abrasio. n haye.b een suggested.B uilt-up edge (BUE) which has a distinct shape was more pro i1ounced at lower cutting speeds, high feed rates and greater depth of cut. The presence of BUE has been found to increase tool life and reduce tool wear but at the expense of surface finish. The increase in tool life or reduction in tool wear is likely due to the protective layer that the BUE formed on the tool surface preventing a direct contact between the tool and chip. Linear regression analysis showed that the value of Taylor exponent n is high (0.8-1.0) compared to the values of n (0.2-0.3) obtained when machining steel. This indicates that the tool life is less sensitive to cutting speed for MMC than it is for steel.
10
Lewis, Christopher Alan. "The internal stress state and related microstructural changes during deformation of AlZrOâ†2 metal matrix composites." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338255.
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11
Alhashmy, Hasan. "Fabrication of Aluminium Matrix Composites (AMCs) by Squeeze Casting Technique Using Carbon Fiber as Reinforcement." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23120.
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Composites have been developed with great success by the use of fiber reinforcements in metallic materials. Fiber reinforced metal matrices possess great potential to be the next generation of advanced composites offering many advantages compared to fiber reinforced polymers. Specific advantages include high temperature capability, superior environmental stability, better transverse modulus, shear and fatigue properties. Although many Metal Matrix Composites (MMCs) are attractive for use in different industrial applications, Aluminium Matrix Composites (AMCs) are the most used in advanced applications because they combine acceptable strength, low density, durability, machinability, availability, effectiveness and cost. The present study focuses on the fabrication of aluminium matrix composite plates by squeeze casting using plain weave carbon fiber preform (AS4 Hexcel) as reinforcement and a matrix of wrought aluminium alloy 1235-H19. The objective is to investigate the process feasibility and resulting materials properties such as hardness at macro- and micro-scale, impact and bend strength. The properties obtained are compared with those of 6061/1235-H19 aluminium plates that were manufactured under the same fabrication conditions. The effect of fiber volume fraction on the properties is also investigated. Furthermore, the characterization of the microstructure is done using Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) in order to establish relationships between the quality of the fiber/aluminium interface bond and mechanical properties of the composites.
In conclusion, aluminium matrix composite laminate plates were successfully produced. The composites show a good chemical bond between the fiber and the aluminium matrix. This bond resulted from heterogeneous precipitation of aluminium carbides (Al4C3) at the interface between aluminium matrix and carbon fiber. The hardness at macro- and micro-scale of the composites increases by over 50% and the flexural modulus increases by about 55%. The toughness of the composite decreases due to the presence of brittle phases which can be improved by better oxidation prevention. Also, an optimal carbon volume fraction was observed that provides optimal properties including peak hardness, peak stiffness and peak toughness.
12
Hambleton, Ruth. "The structure and properties of high temperature aluminium alloys and metal matrix composites." Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266721.
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13
Li, Q. F. "Studies in the solidification behaviour of aluminium alloy/alumina metal matrix composites (MMC's)." Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260364.
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14
Mohamad, Zain Nor Hashimah. "The utilization of Palm Oil Fuel Ash in Aluminium Metal Matrix Composites Materials." Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/78125.
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Palm oil Fuel ash (POFA) are utilize to produce high technology material in Metal Matrix Composites. Using stir casting method, the experiment resulted in an enforced Mechanical and tribological properties of the Aluminium 6061(AL6061) when fabricated with 5vol. % of POFA. The tensile strength is improved when applying POFA size of 76µm
15
Swaminathan, S. "Processing And Characterisation Of Bulk Al2 O3 p /AIN-Al Composites By Pressureless Infiltration." Thesis, Indian Institute of Science, 2000. https://etd.iisc.ac.in/handle/2005/181.
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Al-Mg alloys were infiltrated into porous alumina preforms at temperatures greater than 950°C where significant amount of nitride forms in the matrix. The present work aims to obtain a process window for growing A1N rich composites over uniform thicknesses so that bulk fabrication of these composites could be carried out. Initial experiments were carried out in a thermo-gravimetric analyser (TGA) to establish suitable conditions for growing useful thicknesses. Al- 2wt% Mg alloy, alumina preforms of particle size 53-63μm and N2 - 2% H2 (5ppm O2) were used for the present study based on previous work carried out in the fabrication of MMCs at low temperatures. Experiments carried out in the TGA indicate that oxygen in the system has to be gettered for the growth of nitride rich composites. Infiltration heights of about 8mm were obtained using an external getter (Al - 5wt%Mg) alloy in addition to the base alloy used for infiltration.
The above process conditions were subsequently employed in a tube furnace to fabricate bulk composites and to study the effect of temperature on the volume fraction of aluminium nitride in the matrix. The volume fraction of nitride in the composite varied between 30 and 95 vol % with increase in process temperature from 950°C to 1075°C. Microstructures of these composites indicate that A1N starts to form on the particle surface and tends to grow outwards. The metal supplied through channels adjacent to the particle surface nitride until a point is reached when the composite growing from the adjacent particles meet each other and isolate the melt underneath from nitrogen thereby leading to a metal rich region underneath. Increase in temperature results in an increased nitridation rate resulting in reduced metal pocket size.
Composites fabricated at 975°C had a minor leak at the O-rings, which seal the tube. This led to infiltration under conditions of varying oxygen partial pressure leading to different nitride fractions in the composite. The above fact was confirmed by conducting an experiment with commercial purity nitrogen, which has an oxygen content of about 5000ppm. The composite had an A1N content of about 30% whereas the composite fabricated with N2 -2%H2 (5ppm oxygen) showed a nitride content of 64%. This suggests that one can vary the nitride content in the composite by varying the oxygen content in the system at a particular process temperature.
The hardness of the matrix increases with increase in process temperature from 3.5 ± 0.7 GPa at 975°C to about 9.8 ± 0.9 GPa at 1075°C. Porosity was observed in the composite processed at 1075°C. This increased porosity leads to decreased hardness though the nitride content in the composite has increased by 11%. The scatter in the data is attributed to variations in the microstructure as well as due to interference from underlying metal pockets or particles as well as due to porosity introduced in the composite at high processing temperatures.
16
Swaminathan, S. "Processing And Characterisation Of Bulk Al2 O3 p /AIN-Al Composites By Pressureless Infiltration." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/181.
Full textAbstract:
Al-Mg alloys were infiltrated into porous alumina preforms at temperatures greater than 950°C where significant amount of nitride forms in the matrix. The present work aims to obtain a process window for growing A1N rich composites over uniform thicknesses so that bulk fabrication of these composites could be carried out. Initial experiments were carried out in a thermo-gravimetric analyser (TGA) to establish suitable conditions for growing useful thicknesses. Al- 2wt% Mg alloy, alumina preforms of particle size 53-63μm and N2 - 2% H2 (5ppm O2) were used for the present study based on previous work carried out in the fabrication of MMCs at low temperatures. Experiments carried out in the TGA indicate that oxygen in the system has to be gettered for the growth of nitride rich composites. Infiltration heights of about 8mm were obtained using an external getter (Al - 5wt%Mg) alloy in addition to the base alloy used for infiltration.
The above process conditions were subsequently employed in a tube furnace to fabricate bulk composites and to study the effect of temperature on the volume fraction of aluminium nitride in the matrix. The volume fraction of nitride in the composite varied between 30 and 95 vol % with increase in process temperature from 950°C to 1075°C. Microstructures of these composites indicate that A1N starts to form on the particle surface and tends to grow outwards. The metal supplied through channels adjacent to the particle surface nitride until a point is reached when the composite growing from the adjacent particles meet each other and isolate the melt underneath from nitrogen thereby leading to a metal rich region underneath. Increase in temperature results in an increased nitridation rate resulting in reduced metal pocket size.
Composites fabricated at 975°C had a minor leak at the O-rings, which seal the tube. This led to infiltration under conditions of varying oxygen partial pressure leading to different nitride fractions in the composite. The above fact was confirmed by conducting an experiment with commercial purity nitrogen, which has an oxygen content of about 5000ppm. The composite had an A1N content of about 30% whereas the composite fabricated with N2 -2%H2 (5ppm oxygen) showed a nitride content of 64%. This suggests that one can vary the nitride content in the composite by varying the oxygen content in the system at a particular process temperature.
The hardness of the matrix increases with increase in process temperature from 3.5 ± 0.7 GPa at 975°C to about 9.8 ± 0.9 GPa at 1075°C. Porosity was observed in the composite processed at 1075°C. This increased porosity leads to decreased hardness though the nitride content in the composite has increased by 11%. The scatter in the data is attributed to variations in the microstructure as well as due to interference from underlying metal pockets or particles as well as due to porosity introduced in the composite at high processing temperatures.
17
Coelho, Reginaldo Teixeira. "The machinability of aluminium-based SiC reinforced metal matrix composite (MMC) alloy with emphasis on hole production." Thesis, University of Birmingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340966.
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18
Kolli, Sudhakar. "Joining of aluminum based particulate-reinforced metal-matrix composites /." The Ohio State University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487685204967.
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19
Smith, Joel Edmund. "Development of improved metal matrix composite via the control of interface and matrix microstructure." Thesis, University of Bath, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296330.
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20
Vuorinen, Esa. "Controlling infiltration when brazing P/M parts and during manufacture of aluminium metal matrix composites." Licentiate thesis, Luleå, 2004. http://epubl.luth.se/1402-1757/2004/82.
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21
Kothari, Mitul Arvind. "Welding of cast A359/SiC/10p metal matrix composites." Texas A&M University, 2005. http://hdl.handle.net/1969.1/2699.
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Welding of metal matrix composites (MMCs) is an alternative to their
mechanical joining, since they are difficult to machine. Published literature in fusion
welding of similar composites shows metallurgical problems. This study investigates the
weldability of A359/SiC/10p aluminum SiC MMC. Statistical experiments were
performed to identify the significant variables and their effects on the hardness, tensile
and bending strengths, ductility, and microstructure of the weld. Finite Element
Analysis (FEA) was used to predict the preheat temperature field across the weld and the
weld pool temperature.
Welding current, welding speed, and the preheat temperature (300-350??C)
affected the weld quality significantly. It was seen that the fracture of the welded
specimens was either in the base MMC or in the weld indicating a stronger interface
between the weld and the base MMC. Oxides formation was controlled along the weld
joint. Low heat inputs provided higher weld strengths and better weld integrity. It was
found that the weld strengths were approximately 85% of the parent material strength.
The weld region had higher extent of uniform mixing of base and filler metal when
welded at low currents and high welding speeds. These adequate thermal conditions
helped the SiC particles to stay in the central weld region. The interface reaction
between the matrix and SiC particles was hindered due to controlled heat inputs and
formation of harmful Al4C3 flakes was suppressed. The hardness values were found to
be slightly higher in the base metal rich region. There was no significant loss in the
hardness of the heat affected zone. The ductility of the weld was considerably increased
to 6.0-7.0% due to the addition of Al-Si filler metal.
22
Drury, William James. "Quantitative microstructural and fractographic characterization of AE-Li/FP metal matrix composite." Thesis, Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/19958.
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23
Khan, Kirity Bhusan. "Processing And Characterization Of B4C Particle Reinforced Al-5%Mg Alloy Matrix Composites." Thesis, Indian Institute of Science, 2000. https://etd.iisc.ac.in/handle/2005/182.
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Metal matrix composites (MMCs) are emerging as advanced engineering materials for application in aerospace, defence, automotive and consumer industries (sports goods etc.). In MMCs, a metallic base material is reinforced with ceramic fiber, whisker or particulate in order to achieve a combination of properties not attainable by either constituent individually. Aluminium or its alloy is favoured as metallic matrix material because of its low density, easy fabricability and good engineering properties. In general, the benefits of aluminium metal matrix composites (AMCs) over unreinforced aluminium alloy are increased specific stiffness, improved wear resistance and decreased coefficient of thermal expansion. The conventional reinforcement materials for AMCs are SiC and AI2O3.
In the present work, boron carbide (B4C) particles of average size 40μm were chosen as reinforcement because of its higher hardness (very close to diamond) than the conventional reinforcement like SiC, AI2O3 etc. and of its density (2.52 g cm"3) very close to Al alloy matrix. In addition, due to high neutron capture cross-section of 10B isotope, composites containing B4C particle reinforcement have the potential for use in nuclear reactors as neutron shielding and control rod material. Al-5%Mg alloy was chosen as matrix alloy to utilize the beneficial role of Mg in improving wettability between B4C particles and the alloy melt. (Al-5%Mg)-B4C composites containing 10 and 20 vol% B4C particles were fabricated. For the purpose of inter-comparison, unreinforced Al-5%Mg alloy was also prepared and characterized. The Stir Cast technique, commonly utilized for preparation of Al-SiC, was adapted in this investigation.The Composites thus prepared was subsequently hot extruded with the objective of homogenization and healing minor casting defects. Finally the unreinforced alloy and its composites were characterized in terms of their microstructure, mechanical and thermo-physical properties, sliding wear behaviour and neutron absorption characteristics.
The microstructures of the composites were evaluated by both optical microscope and scanning electron microscope (SEM). The micrographs revealed a relatively uniform distribution of B4C particles and good interfacial integrity between matrix and B4C particles.
The hot hardness in the range of 25°C to 500°C and indentation creep data in the range of 300°C to 400°C show that hot hardness and creep resistance of Al-Mg alloy is enhanced by the presence of B4C particles. Measurement of coefficient of thermal expansion (CTE) of composites and unreinforced alloy upto 450°C showed that CTE values decrease with increase in volume fraction of reinforcement.
Compression tests at strain rates, 0.1, 10 and 100 s-1 in the temperature range 25 - 450 °C showed that the flow stress values of composites were, in general, greater than those of unreinforced alloy at all strain rates. These tests also depicted that the compressive strength increases with increase in volume fraction of reinforcements. True stress values of composites and unreinforced alloy has been found to be a strong function of temperature and strain rate. The kinetic analysis of elevated temperature plasticity of composites revealed higher stress exponent values compared to unreinforced alloy. Similarly, apparent activation energy values for hot deformation of composites were found to be higher than that of self-diffusion in Al-Mg alloy.
Tensile test data revealed that the modulus and 0.2% proof stress of composites increase with increase in volume fraction of the reinforcements. Composites containing 10%BUC showed higher ultimate tensile strength values (UTS) compared to unreinforced alloy. However, composites with 20%B4C showed lower UTS compared to that of the unreinforced alloy. This could be attributed to increased level of stress concentration and high level of plastic constraint imposed by the reinforcing jparticles or due to the presence solidification-induced defects (pores and B4C agglomerates ).
Sliding wear characteristics were evaluated at a speed of 1 m/s and at loads ranging from 0.5 to 3.5kg using a pin-on-disc set up. Results show that wear resistance of Al-5%Mg increases with the addition of B4C particles. Significant improvement in wear resistance of Al-5%Mg is achieved with the addition of 20% B4C particles. SEM examination of worn surfaces showed no pull-out of reinforcing particles even at the highest load of 3.5 kg, thus confirming good interfacial bonding between dispersed B4C particles and Al alloy matrix.
The neutron radiography data proved that (Al-5%Mg)-B4C composites possess good neutron absorbing characteristics.
From the experimental data evaluated in the "study, it may be concluded that (Al-5%Mg)-B4C composites could be a candidate material for neutron shielding and control rod application.
The enhanced elevated temperature-strength and favourable neutron absorption characteristics of these composites are strong points in favour of this material.
24
Khan, Kirity Bhusan. "Processing And Characterization Of B4C Particle Reinforced Al-5%Mg Alloy Matrix Composites." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/182.
Full textAbstract:
Metal matrix composites (MMCs) are emerging as advanced engineering materials for application in aerospace, defence, automotive and consumer industries (sports goods etc.). In MMCs, a metallic base material is reinforced with ceramic fiber, whisker or particulate in order to achieve a combination of properties not attainable by either constituent individually. Aluminium or its alloy is favoured as metallic matrix material because of its low density, easy fabricability and good engineering properties. In general, the benefits of aluminium metal matrix composites (AMCs) over unreinforced aluminium alloy are increased specific stiffness, improved wear resistance and decreased coefficient of thermal expansion. The conventional reinforcement materials for AMCs are SiC and AI2O3.
In the present work, boron carbide (B4C) particles of average size 40μm were chosen as reinforcement because of its higher hardness (very close to diamond) than the conventional reinforcement like SiC, AI2O3 etc. and of its density (2.52 g cm"3) very close to Al alloy matrix. In addition, due to high neutron capture cross-section of 10B isotope, composites containing B4C particle reinforcement have the potential for use in nuclear reactors as neutron shielding and control rod material. Al-5%Mg alloy was chosen as matrix alloy to utilize the beneficial role of Mg in improving wettability between B4C particles and the alloy melt. (Al-5%Mg)-B4C composites containing 10 and 20 vol% B4C particles were fabricated. For the purpose of inter-comparison, unreinforced Al-5%Mg alloy was also prepared and characterized. The Stir Cast technique, commonly utilized for preparation of Al-SiC, was adapted in this investigation.The Composites thus prepared was subsequently hot extruded with the objective of homogenization and healing minor casting defects. Finally the unreinforced alloy and its composites were characterized in terms of their microstructure, mechanical and thermo-physical properties, sliding wear behaviour and neutron absorption characteristics.
The microstructures of the composites were evaluated by both optical microscope and scanning electron microscope (SEM). The micrographs revealed a relatively uniform distribution of B4C particles and good interfacial integrity between matrix and B4C particles.
The hot hardness in the range of 25°C to 500°C and indentation creep data in the range of 300°C to 400°C show that hot hardness and creep resistance of Al-Mg alloy is enhanced by the presence of B4C particles. Measurement of coefficient of thermal expansion (CTE) of composites and unreinforced alloy upto 450°C showed that CTE values decrease with increase in volume fraction of reinforcement.
Compression tests at strain rates, 0.1, 10 and 100 s-1 in the temperature range 25 - 450 °C showed that the flow stress values of composites were, in general, greater than those of unreinforced alloy at all strain rates. These tests also depicted that the compressive strength increases with increase in volume fraction of reinforcements. True stress values of composites and unreinforced alloy has been found to be a strong function of temperature and strain rate. The kinetic analysis of elevated temperature plasticity of composites revealed higher stress exponent values compared to unreinforced alloy. Similarly, apparent activation energy values for hot deformation of composites were found to be higher than that of self-diffusion in Al-Mg alloy.
Tensile test data revealed that the modulus and 0.2% proof stress of composites increase with increase in volume fraction of the reinforcements. Composites containing 10%BUC showed higher ultimate tensile strength values (UTS) compared to unreinforced alloy. However, composites with 20%B4C showed lower UTS compared to that of the unreinforced alloy. This could be attributed to increased level of stress concentration and high level of plastic constraint imposed by the reinforcing jparticles or due to the presence solidification-induced defects (pores and B4C agglomerates ).
Sliding wear characteristics were evaluated at a speed of 1 m/s and at loads ranging from 0.5 to 3.5kg using a pin-on-disc set up. Results show that wear resistance of Al-5%Mg increases with the addition of B4C particles. Significant improvement in wear resistance of Al-5%Mg is achieved with the addition of 20% B4C particles. SEM examination of worn surfaces showed no pull-out of reinforcing particles even at the highest load of 3.5 kg, thus confirming good interfacial bonding between dispersed B4C particles and Al alloy matrix.
The neutron radiography data proved that (Al-5%Mg)-B4C composites possess good neutron absorbing characteristics.
From the experimental data evaluated in the "study, it may be concluded that (Al-5%Mg)-B4C composites could be a candidate material for neutron shielding and control rod application.
The enhanced elevated temperature-strength and favourable neutron absorption characteristics of these composites are strong points in favour of this material.
25
Mendes, Luís Gonçalves. "Production of aluminium based composites reinforced with embedded NiTi by friction stir welding." Master's thesis, Faculdade de Ciências e Tecnologia, 2012. http://hdl.handle.net/10362/8764.
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Dissertação para a obtenção do grau de Mestre em Engenharia MecânicaAluminium alloys have been widely used in composite materials in order to promote an enhancement in its properties while reducing weight. As in the production of new composites with a significant difference in mechanical and thermo-physical properties fusion welding processes enhances the formation of undesired intermetallics. Those limitations have driven research on solid state technologies, such as Friction Stir Welding (FSW), for joining dissimilar materials. This study aimed to develop composites in AA 1XXX series aluminium alloys with NiTi by FSW. Different reinforcing material shapes were investigated, analyzed the interfaces and the resulting material flow. The final product was mechanically characterized. It was observed an increase of 70 % of ultimate tensile strength, compared to Al base material and yielding between the two dissimilar materials was greater than the Al lap joint yield stress. The final composite depicted a good electrical conductivity, reducing less than 3 % IACS of the Al base material. Thus, a composite with a strong mechanical bonding was produced, maintaining the original functional properties of the reinforcement NiTi alloy, and the electrical properties of the Aluminium.
FCT/MCTES - "Desenvolvimento da tecnologia de processamento por fricção linear para produzir materiais com gradiente de funcionalidade e melhoria de superfícies para aplicações avançadas de engenharia – FRISURF"
26
Famodimu, Omotoyosi Helen. "Additive manufacturing of aluminium-metal matrix composite developed through mechanical alloying." Thesis, University of Wolverhampton, 2016. http://hdl.handle.net/2436/620337.
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Laser melting of aluminium alloy - AlSi10Mg has increasingly been used to create specialised products in aerospace and automotive applications. However, research on utilising laser melting of Aluminium matrix composites in replacing specialised parts have been slow on the uptake. This has been attributed to the complexity of the laser melting process, metal/ceramic feedstock for the process and the reaction of the feedstock material to the laser. Thus an understanding of the process, material microstructure and mechanical properties is important for its adoption as a manufacturing route of Aluminium Metal Matrix Composites. The effect of the processing parameters (time and speed) on embedding the Silicon Carbide onto the surface of the AlSi10Mg alloy was initially investigated in Phase 1 and 2 of the research. The particle shape and maximum particle size for each milling time and speed was analysed in determining a suitable starting powder for the Laser Melting phase. An ideal shape and size for the composite powder was obtained at 500 rev/min when milled for 20 mins. The effects of several parameters of the Laser Melting process on the mechanical blended composite were investigated. Single track formations of the matrix alloy, 5% Aluminium Metal Matrix Composites and 10% Aluminium Metal Matrix Composites were studied for their reaction to the laser melting in Phase 3. Subsequently in Phase 4, density blocks were studied at different scan speeds and step-over for surface roughness, relative density and porosity. These were utilised in determining a process window to fabricate near fully dense components. Phase 5 of the research focused on microstructural and mechanical properties of the laser melted matrix alloy using the normal parameters for the matrix alloy and the modified LM parameters for the composite powders. Test coupons were built in one orientation and some coupons were heat-treated to initiate precipitation-hardening intermetallics in the matrix and composite. This study investigates the suitability of the mechanical alloying as a novel method of producing feedstock material for the LM process. This research further explores the interaction of the composite powders with the laser until suitable process parameters were obtained. Furthermore, the fractography, mechanical and microstructural evolution of the Al/SiC composite, with different percentage volume reinforcement manufactured by the LM and subsequently heat treated, was explored for the first time.
27
Tu, Zhiqiang. "Fabrication and Mechanical Properties of Carbon Fiber Reinforced Aluminum Matrix Composites by Squeeze Casting." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/40523.
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Rapid modern technological changes and improvements bring great motivations in advanced material designs and fabrications. In this context, metal matrix composites, as an emerging material category, have undergone great developments over the past 50 years. Their primary applications, such as automotive, aerospace and military industries, require materials with increasingly strict specifications, especially high stiffness, lightweight and superior strength. For these advanced applications, carbon fiber reinforced aluminum matrix composites have proven their enormous potential where outstanding machinability, engineering reliability and economy efficiency are vital priorities.
To contribute in the understanding and development of carbon fiber reinforced aluminum matrix composites, this study focuses on composite fabrication, mechanical testing and physical property modelling. The composites are fabricated by squeeze casting. Plain weave carbon fiber (AS4 Hexcel) is used as reinforcement, while aluminum alloy 6061 is used as matrix. The improvement of the squeeze casting fabrication process is focused on reducing leakage while combining thermal expansion pressure with post-processing pressing. Three different fiber volume fractions are investigated to achieve optimum mechanical properties. Piston-on-ring (POR) bend tests are used to measure the biaxial flexural stiffness and fracture strength on disc samples. The stress-strain curves and fracture surfaces reveal the effect of fiber-matrix interface bonding on composite bend behaviour. The composites achieved up to 11.6%, 248.3% and 90.1% increase in flexural modulus, strain hardening modulus and yield strength as compared with the unreinforced aluminum alloy control group, respectively. Analytical modelling and finite element modelling are used to comparatively characterise and verify the composite effective flexural modulus and strength. Specifically, they allowed
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evaluating how far the experimental results deviate from idealized assumptions of the models, which provides an insight into the composite sample quality, particularly at fiber-matrix interfaces. Overall, the models agree well with experimental results in identifying an improvement in flexural modulus up to a carbon fiber volume fraction of 4.81vol%. However, beyond a fiber content of 3.74vol%, there is risk of deterioration of mechanical properties, particularly the strength. This is because higher carbon fiber volume fractions restrict the infiltration and wetting of carbon fibre by the liquid, potentially leading to poor fiber-matrix interface bonding. It is shown that higher thermal expansion pressures and subsequent post-processing pressing can overcome this challenge at higher carbon fiber volume contents by reducing fiber-aluminum contact angle, improving infiltration, reducing defects such as porosity, and overall improving fiber-matrix bonding.
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Park, Conrad. "Mechanical Performance and Structure-Property Relations in6061B Aluminum Metal Matrix Composites." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1547842396716777.
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Madgwick, Alexander. "Creep and damage in an A359 aluminium alloy/SiC metal matrix composite." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620311.
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Yıldırım, Uygar Güden Mustafa. "Investigation of quasi-static dynamic mechanical properties of functionally graded Sic-particulate reinforced aluminium metal matrix composites/." [s.l.]: [s.n.], 2004. http://library.iyte.edu.tr/tezler/master/makinamuh/T000470.doc.
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Clews, Justin David. "Ultrasonic consolidation of continuous fiber metal matrix composite tape." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 190 p, 2009. http://proquest.umi.com/pqdweb?did=1885474451&sid=1&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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DONNINI, RICCARDO. "Metal matrix composite: structure and technologies." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2009. http://hdl.handle.net/2108/868.
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I compositi a matrice metallica sono materiali aventi elevate potenzialità di applicazione, i cui punti critici riguardano soprattutto le tecnologie di produzione e le lavorazioni alle macchine utensili.
Un composito a matrice di titanio rinforzato con lunghe fibre unidirezionali in SiC, il Ti6Al4V-SiCf, è candidato per componenti di turbine aeronautiche soggette a medie temperature (fino a 600°C) per lunghi tempi di esposizione. Per questo ne sono state esaminate sia le reazioni di tipo microchimico, le quali accadono soprattutto nell’interfaccia fibra/matrice, sia le proprietà meccaniche. La microstruttura allo stato tal quale e dopo lunghi trattamenti termici (fino a 100 ore e 600°C) è stata esaminata mediante diffrazione ai raggi X (XRD), spettrometria elettronica (SEM/EDS), spettroscopia di fotoemissione (XPS) e spettroscopia Auger (AES). Il comportamento meccanico, anche qui sia allo stato tal quale che dopo trattamenti termici, è stato studiato attraverso prove ad indentazione strumentata (FIMEC), di modulo dinamico, prove di trazione e di fatica. Inoltre sono state eseguite prove di frizione interna per verificare il caratteristico comportamento anelastico del materiale, durante condizioni di elevato stato vibrazionale e di alta temperatura. Lo studio, sviluppato sullo stesso composito prodotto però mediante due processi di fabbricazione differenti come Hot Isostatic Pressure and Roll Diffusion Bonding, ha confermato l’idoneità del materiale alle applicazioni considerate.
Per quanto riguarda lo studio della lavorabilità, sono stati studiati, dal punto di vista dell’operazione di foratura, i materiali compositi a matrice di alluminio rinforzati a fibre corte o particolato, valutando le migliori condizioni di riduzione delle forze di taglio, soprattutto in funzione delle temperatura del pezzo da forare.Metal matrix composites are materials having high application potentiality, whose critical points regards especially production technology and machining. A titanium matrix composite reinforced by unidirectional SiC fibers, Ti6Al4V-SiCf , is candidate to components of aeronautical turbines subjected at middle temperatures (500-600°C) for long exposure time. It has been examined about the micro-chemical reactions, occurring especially on the fiber-matrix interface, and the mechanical properties. The microstructure, in as-fabricated condition and after long-term heat treatments simulating the work condition has been investigated by means of high-temperature X-ray diffraction (XRD), energy dispersion spectrometry (SEM/EDS), X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). The mechanical behaviour, in as-fabricated condition and after heat treatments, have been inspected by instrumented indentation (FIMEC), dynamic modulus, tensile and fatigue tests. Moreover, to the verify the characteristic anelastic phenomena for the composite, internal friction probes have been carried out by using a vibrating reed technique with electrostatic excitation and frequency modulation detection of flexural vibration. The study has been developed on the same composite produced by two different fabrication process, Hot Isostatic Pressure and Roll Diffusion Bonding, confirming the suitable of the material for the considered applications. About the composite machining, aluminium matrix composite reinforced by short fiber or particle has been studied about drilling operations, evaluating the better condition to reduce the cutting forces (thrust and torque), especially as function of the workpiece temperature (hot drilling)
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Muley, Aniruddha Vinayak. "Fabrication, characterization and tribological studies on aluminum based hybrid metal matrix composites." Thesis, IIT Delhi, 2016. http://localhost:8080/xmlui/handle/12345678/7090.
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Mitchell, Colin A. "A study of the powder processing, tribological performance and metallurgy of Aluminium-based, discontinuously reinforced metal matrix composites." Thesis, Edinburgh Napier University, 2002. http://researchrepository.napier.ac.uk/Output/3807.
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The principal objectives of the research reported in this thesis are: to determine the effect that sinter time has on the metallurgical behaviour of alumina-reinforced aluminium-606lmatrix composites; compare and assess the wear resistance of alumina and silicon carbide reinforced aluminium 6061-matrix composites, together with monolithic aluminium 6061 alloy; determine the effect that reinforcement particle size has on the wear resistance of aluminium 6061-matrix composites; identify the relative merits of two techniques for depositing copper coatings on to alumina reinforcements. Through investigation, a successful method of processing silicon carbide and alumina particulate-reinforced AA6061 composites, fabricated by cold uniaxial pressing with vacuum sintering, has been determined. The processing route is as follows: pressing at 400 MPa; vacuum sinter at 600°C for 30 minutes; solution heat treat for 30 minutes at 530°C then water quench; precipitation (ageing) heat treat for 7 hours at I 75°C, then air cool. Metallurgical examination of composites revealed that magnesium was found to collect at interface regions around alumina particulates, resulting in the depletion of magnesium from the aluminium 6061 matrix. The severe depletion of magnesium from the AA6061 matrix when alumina is used as a reinforcement was found to occur during long (greater than 30 minutes) sintering times using a sintering temperature of 600°C. It is postulated that the formation of spinel (MgA12O4) formed from the reaction of magnesium with alumina is a probable cause for the Mg migration. The composites containing alumina particulates were found to have lower hardness values than the monolithic alloy and composites containing silicon carbide, when sintering took place for longer than 30 minutes. Adding 5 wt% silicon to the AA6061 matrix in composites reinforced with alumina particulates was found to reduce the magnesium depletion for sinter times up to one hour at 600°C and give improved composite bulk hardness. During the research, a need for an improved wear testing machine was identified. Therefore a wear test rig, which allows samples of different materials (under different applied loads if required) to be tested simultaneously without interference between test pieces, was designed and commissioned. Two electroless methods for copper coating alumina particulates were also investigated. One method used formaldehyde as the reducing agent, while the other employed hydrazine-hydrate as the reducing agent. The latter method has proven to be quicker, and with improved results, compared to the traditional method using formaldehyde as the reducing agent.
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Peng, Tao. "Processing and characterization of multi-walled carbon nanotube reinforced aluminium metal matrix composite." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6593/.
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Aluminium(Al) is widely utilised in the packaging, transportation, electrical and modern machinery sections because of its low density, high specific strength, excellent corrosion resistance, impressive electrical and thermal conductivity, abundance and recyclability. However, relatively low strength is the most significant challenge for aluminium to be applied in wider area. To solve this problem, carbon nanotube was projected as the most ideal reinforcement due to its incomparable specific strength and elastic modulus, exceptional electrical and thermal conductivity. It is assumed that carbon nanotube can not only strengthen but also introduce various distinctive characteristics into the aluminium matrix to improve its overall properties and performances. In the current research, 0.5 wt. % – 2.0 wt. % of mutil-walled carbon nanotube was ball milled with aluminium powders for 5 – 20h. The microstructure of the as-milled composite powders and as-sintered bulk composite specimens were characterized by particle size analysis, optical microscopy and scanning electron microscopy(SEM). Also, the evolution and dispersion of MWNT were studied by Raman spectroscopy and SEM. Moreover, the as-produced composites were subjected to standard Vickers hardness test and MPIF standard tensile test to investigate the mechanical properties of the composite.
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Yu, Hao. "Processing Routes for Aluminum based Nano-Composites." Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-theses/367.
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The term "Metal Matrix Nano-Composites (MMNCs)" broadly refers to a composite system that is based on metal or alloy substrate, combined with metallic or non-metallic nano-scale reinforcements. The main advantages of MMNCs include excellent mechanical performance, feasible to be used at elevated temperatures, good wear resistance, low creep rate, etc. In the recent past, MMNCs have been extensively studied, especially the method of fabrication as the processing of such composites is quite a challenge. Though a variety of processing methods have been explored and studied over the years, none have emerged as the optimum-processing route. The major issue that needs to be addressed is the tendency of nano-sized particles to cluster and also the challenge as to how to disperse them in the bulk melt. This work explored the feasibility of utilizing Lorentz forces to address both of these critical issues: clustering and dispersion. The work was carried out both theoretically as well as with accompanying validation experiments. The results indicate that Lorentz Forces may be viable and should be considered in the processing of MMNCs.
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Dadbakhsh, Sasan. "Mechanical engineering : the selective laser melting of metals and in-situ aluminium matrix composites." Thesis, University of Exeter, 2012. http://hdl.handle.net/10036/3840.
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Selective laser melting (SLM) is an additive manufacturing technique to produce complex three-dimensional parts through solidifying successive layers of powder materials on top of each other, from the bottom to top. The powder base nature allows the SLM to process a wide variety of materials and their mixtures and fabricate advanced and complicated composite parts. However, the SLM is a newly established process and seeks detailed scientific studies to develop new materials systems for the consumption of industry. These scientific studies are particularly important because of many issues associated with the SLM process, such as porosity, balling, delamination, thermal stress, etc, which can be varied from one material system to another. This PhD project aims to elucidate the fundamental mechanisms governing the microstructure and mechanical properties of the metallic and in-situ Al matrix composite parts made by SLM. The research starts with a preliminary study on SLM of stainless steel in order to explore the usage of SLM machine and related parameters. It illustrates the effect of part layout on the quality of products. The main research focuses on the in-situ formation of particulate reinforced Al matrix by using SLM of Al/Fe2O3 powder mixture. It is a pioneering research to integrate in-situ interaction with laser melting to produce advanced Al composites. It investigates the mechanisms governing SLM assisted in-situ reaction and also the effects of various parameters such as SLM layer thickness, laser power and scanning speed as well as the proportion of Fe2O3. It examines the influence of Al alloy powder and it describes the effect of hot isostatic pressing (HIP) post-treatment. The physical, mechanical, and metallurgical properties of the products are extensively assessed using various techniques. The processing windows of the process are sketched. The findings demonstrate unique microstructural features due to combined in-situ reaction and laser rapid consolidation, and contribute to provision of an in-depth scientific understanding of novel Al matrix composites by using SLM assisted in-situ processes. As part of this PhD project, industrial collaborative research has also been conducted to characterise the surface finish, metallurgical quality, process accuracy and mechanical properties of various SLM made metallic parts using Al, Ti, stainless steel, and super alloys. This part of research has generated scientific data and results for industrial applications of metallic fabrication using SLM.
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Yang, Xinliang. "Particle dispersion in aluminium and magnesium alloys." Thesis, Brunel University, 2016. http://bura.brunel.ac.uk/handle/2438/14437.
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High shear mixing offers a promising solution for particle dispersion in a liquid with intensive turbulence and high shear rate, and has been widely used in the chemical, food and pharmaceutical industries. However, a practical high shear mixing process has not yet been adapted to solve the particle agglomeration in metallurgy due to the high service temperature and reactive environment of liquid metal. In this study, the effect of high shear mixing using the newly designed rotor-stator high shear device have been investigated with both Al and Mg matrix composites reinforced with SiC particles through casting. The microstructural observation of high shear treated Al and Mg composites show improved particle distribution uniformity in the as-cast state. Increased mechanical properties and reduced volume fraction of porosity are also obtained in the composite samples processed with high shear. With the melt conditioning procedure developed for twin roll casting process, two distinct solutions has been provided for thin gauge Mg strip casting with advanced microstructure and defect control. The melt conditioning treatment activates the MgO as heterogeneous nuclei of α-Mg through dispersion from continuous films to discrete particles. Thus enhanced heterogeneous nucleation in the twin roll casting process not only refines the α-Mg grain size but also eliminates the centre line segregation through equiaxed grain growth and localized solute distribution. The grain refinement of the α-Mg through SiC addition has also been studied through EBSD and crystallographic approaches. Two reproducible and distinct crystallographic orientation relationships between α-SiC (6H) and α-Mg have been determined: [1010]SiC//[2113]Mg, (0006)SiC//(1011)Mg, (1216)SiC//(2202)Mg and [0110]SiC//[1100]Mg, (0006)SiC// (0002)Mg, (2110)SiC//(1120)Mg.
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Hayes, Ian. "Microstructural characterisation and heat treatment refinement of a particulate reinforced aluminium metal matrix composite." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8077/.
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The purpose of this work was to determine the microstructure and secondary phase distribution in the TiB2 particulate reinforced Al-4.5Cu A205 alloy. This was extended to sand, investment and die casting techniques with the overall aim of optimising the existing solution heat treatment protocol for a variety of possible starting conditions. Additional work was aimed at determining a relationship between TiB2 additions and the observed globular microstructure. Hardness testing, DSC analysis, EDS and tensile testing were used to determine the effectiveness of heat treatment. It was found that a 4hr solution treatment at 538oC did not produce significantly different results from a 44hr, four step treatment process. As the diffusion behaviour of Cu was judged to be the most important factor affecting solution heat treatment, a simple microstructural model of typical A205 grain structures was proposed. The model was found to operate on similar timescales to those observed from experimental testing of A205 but was limited by idealised phase structures. The castability of A205 was determined using fluidity and hot tearing experiments. The better than expected castability was attributed to enhanced feeding brought about by the globular structure of A205.
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Dash, Lawrence Christopher. "The mechanism of corrosion and corrosion control of aluminum/graphite metal matrix composites /." The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487588249825594.
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Forde, John. "The elevated temperature performance of cast aluminium alloys and the development of a cast aluminium-copper metal matrix composite." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6419/.
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The first phase of this thesis characterised the currently commercially available L169 and A201 aluminium alloys in terms of their response to testing at the operating parameters predicted for next generation aero-engine components. The L169 and A201 alloys were initially subjected to ageing trials at 205°C, specimens of both alloys were then fatigue tested at ambient temperature and at 205°C following 1000 hours exposure at 205°C. Detailed micrographic characterisation was undertaken to assess the impact of prolonged elevated temperature exposure on the alloy microstructure. Fractography was undertaken on the failed fatigue specimens to assess the impact of ageing temperature and temperature exposure on fatigue behaviour. The L169 alloy exhibited a significant reduction in properties following 1000 hours exposure at 205°C due to extensive precipitate coarsening. The A201 exhibited comparably better elevated temperature performance due to the increased stability of the Ω- phase precipitate however the extensive shrinkage porosity observed in the alloy had a negative impact on fatigue performance and will limit its use in a pressure tight environment. In addition to the investigation into currently commercially available alloys a detailed investigation was taken into a novel dilute aluminium-copper based castable metal matrix composite with the potential for use at elevated temperatures. This alloy exhibits unique solidification mechanisms which result in an increased resistance to conventional aluminium copper alloy casting defects such as shrinkage porosity, segregation and hot tearing. A detailed investigation was undertaken to assess the impact of chemical composition on the alloys unique solidification behaviour and to assess whether there was any possibility for further optimisation. Following on from this investigation the alloy was characterised in similar terms to the L169 and A201 alloys in terms of its fatigue behaviour at both ambient and elevated temperatures to provide an assessment of the alloys potential to meet the predicted next generation aero-engine component operating conditions.
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Stein, Julien. "AA5083 aluminium alloys reinforced with multi-walled carbon nanotubes : microstructure and mechanical properties." Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20002.
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Cette étude a pour but de développer de nouveaux matériaux composites à matrice métallique renforcés par des nanotubes de carbone (CNT) et présentant des propriétés mécaniques améliorées. La majeure partie de ce travail a été réalisée en utilisant des CNT multi-feuillets synthétisés par déposition chimique en phase vapeur en tant que renforts et un alliage d'aluminium AA5083 comme matrice. Des composites CNT/AA5083 denses et homogènes ont été élaborés par le procédé de métallurgie des poudres suivi par une étape de mise en forme, l'extrusion. L'homogénéité de la dispersion des CNT à l'échelle microscopique dans les composites s'avère être un paramètre clé pour l'amélioration des propriétés mécaniques. Ceci a été réalisé par broyage planétaire à haute énergie impliquant des mécanismes de déformation plastique et de soudure à froid et a été démontré à l'aide d'études cartographiques par spectroscopie Raman. La limite d'élasticité, la résistance à la traction et la micro-dureté des composites homogènes ont été augmentées jusqu'à respectivement 55%, 61% et 33% en comparaison avec l'alliage sans CNT et préparé dans les mêmes conditions. Le coefficient de dilatation thermique a été quant à lui réduit de 10%. Les propriétés optimales ont été obtenues pour des concentrations en CNT de 1,5 % en masse. Le renforcement du matériau a été principalement attribué au transfert de charge à l'interface CNT/matriceThe overall goal of this thesis is to process new metal matrix composites reinforced by CNT with enhanced mechanical properties. The main part of this work was achieved using CVD-grown multi-walled CNT as reinforcement and a high-performance light aluminium alloy, AA5083, as the matrix. Dense and homogeneous CNT/AA5083 composites were processed by the powder metallurgy route, followed by an extrusion forming process. A homogeneous dispersion of the CNT in the composites at the micron scale appears to be a key parameter for improving the mechanical properties. This could be achieved using high energy ball milling through the mechanisms of plastic deformation and cold-welding, and was demonstrated from Raman spectroscopy cartography studies. Yield strength, ultimate tensile strength and micro-hardness of the homogeneous composites were increased by up to 55%, 61% and 33%, with respect to raw alloys processed in the same conditions, and the coefficient of thermal expansion was decreased by 10%. Optimal results were obtained with a CNT con-tent of 1.5 wt.-%. The material strengthening was principally attributed to load transfer at the CNT/matrix interface
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CHEN, XIANG. "Fabrication and properties of particulate reinforced aluminum matrix composites by spontaneous infiltration." Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2529525.
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Metal matrix composites has been developed over decades and gradually formed an important part in materials system. Nowadays in the popularization of metal matrix composites, in emphasis for composite materials is changing from a performance-driven to a cost-driven environment. Therefore it’s necessary and important to develop economical efficient techniques for producing metal matrix composites.
Spontaneous infiltration (also called pressureless infiltration) is one of the most cost efficient liquid state techniques for manufacturing metal matrix composites, which uses adhesion forces between the matrix melt and the solid preform to realize the infiltration of matrix into porous preform. However there are several shortcomings in the existing approaches of spontaneous infiltration. For example, low infiltration rate, undesired contamination (AlN in the PREMEXTM process) and poor mechanical properties of the initial product etc.
In this paper an innovative approach of spontaneous infiltration for fabricating particulate reinforced aluminum matrix composites was presented and researches were focused on the problems related with the thermodynamics and kinetics of this approach. TiB2, SiO2, sand, TiO2 etc. ceramic particulates and Al powder were selected as the starting materials, 6060 alloy was chosen as the matrix material. Mixture of TiB2-Al, SiO2-Al, sand-Al, TiO2-Al, TiB2-SiO2-Al or TiB2-sand-Al were prepared to make the preforms by cold pressing.
The blending of Al powder into ceramic particulates was found essential to the spontaneous infiltration. Al powder was believed to improve the wettability of ceramics by reacting or communicating with them ahead of the infiltration. Infiltration temperature and cold pressing pressure were found to have influence on the infiltration. For TiB2-Al, higher temperature or pressure would promote the infiltration. During the infiltration, external melt did not fill all the pores along the infiltration path but preferentially infiltrated part of the pores throughout the preform in the beginning and then gradually spread to the rest of the pores. For TiO2 the infiltration kinetics was more complicated, the reactions with Al increased the volume of solid phases which could block the infiltration paths and even break the preform.
Some properties of PAMCs in TiB2-SiO2-Al series fabricated by spontaneous infiltration at 900 oC for 1 hour were obtained. Both of TiB2 and Al2O3 had a positive influence on improving the defect insensitive properties such as increasing elastic modulus, Vickers hardness and controlling CTE. However the flexural strength property increased with TiB2 fraction but decreased with Al2O3 fraction. Fracture analysis shows TiB2 particles had a good bonding with matrix and Al2O3 particles had a poor bonding with matrix and even some pores were found around them.
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Uribe, Restrepo Catalina. "Process-dependent microstructure and severe plastic deformation in SiCp?? reinforced aluminum metal matrix composites." Master's thesis, University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4712.
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Discontinuously reinforced MMCs with optimized microstructure are sought after for exceptional high strain rate behavior. The microstructure evolution of a stir-cast A359 aluminum composite reinforced with 30 vol.% SiCsubscript p] after isothermal anneal, successive hot-rolling, and high strain rate deformation has been investigated. Quantitative microstructural analysis was carried out for the as-cast, annealed (470??C, 538??C and 570??C) and successively hot rolled specimens (64, 75, 88, and 96% rolling reductions). Selected composites were also examined after high strain rate deformation. X-ray diffraction, optical microscopy, scanning electron microscopy and transmission electron microscopy were employed for microstructural characterization. The strength and ductility of the A359 Al alloys, and the composite, were greatly influenced by the brittle eutectic silicon phase and its morphology. Lamellar eutectic silicon spheroidized with isothermal anneal and successive hot rolling with a corresponding decrease in hardness. The hot rolling process also considerably decreased the SiC particle size (approximately 20% after 96% reduction) by breaking-up the hard SiC particles. However, this break-up of particles increased the homogeneity of SiCsubscript p] size distribution. Successive hot rolling also healed voids due to solidification shrinkage, incomplete infiltration of molten Al and defects originating from fractured particles. Four selected specimens of composites were examined after high strain rate deformation. Fractography and metallographic analysis for the craters, voids, and relevant regions affected by the high velocity impact were carried out. The deposition of impact residuals was frequently observed on the exposed fracture surfaces. These residuals were typically observed as "molten-and-solidified" as a consequence of excessive heat generated during and after the damage.; Particularly in regions of entry and exit of impact, intermixing of residuals and composite constituents were observed, demonstrating that the Al matrix of the composite also had melted. In all samples examined, cracks were observed to propagate through the eutectic Si network while a small number of broken reinforcement particles were observed. A slight variation in failure mechanisms was observed (e.g., radial, fragmentation, petalling) corresponding to the variation in ductility against high strain rate deformation. In selected specimens, parallel sub-cracks at the exit were observed at 45?? and 30??. These sub-cracks were again filled with intermixed constituents from projectile residuals and composites. This observation suggests that the melting of composite constituents that leads to intermixing occured after the crack propagation and other damage.ID: 030646232; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; On t.p. "p??" is subscript.; Thesis (M.S.M.S.E.)--University of Central Florida, 2011.; Includes bibliographical references (p. 86-88).
M.S.M.S.E.
Masters
Materials Science Engineering
Engineering and Computer Science
Materials Science and Engineering
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Lalet, Grégory. "Composites aluminium/fibres de carbone pour l'électronique de puissance." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2010. http://tel.archives-ouvertes.fr/tel-00538480.
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L'étude a pour objectif l'amélioration de la fiabilité des assemblages électroniques à travers la mise en œuvre de drains composites aluminium/fibres de carbone. Le travail a consisté à 1) modéliser, par la méthode des éléments finis, l'influence des propriétés thermiques et mécaniques du matériau de semelle sur l'assemblage életronique ; 2) élaborer (par frittage sous charge uniaxiale, frittage flash et extrusion à chaud) des matériaux composites aluminium/fibres de carbone ; et 3) lier les microstructures observées aux paramètres des procédés d'élaboration ainsi qu'aux propriétés thermiques et mécaniques mesurées.
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Jiang, Xia. "Development of Al alloy composites by powder metallurgy routes." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:ee89b51e-386d-48c8-8f45-161e94490fb6.
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Particulate reinforced Al alloy composites (AlMCs) are recognized as important structural materials due to their lightweight, high modulus and strength and high wear resistance. In order to understand the effect of matrix, reinforcement and secondary processing techniques on the microstructure development and mechanical properties of AlMCs produced by powder metallurgy routes, Al alloy composites reinforced with three types of reinforcements by different secondary processing techniques have been produced and examined. Fabrication of Al or 6061Al alloy based composites reinforced with nano-sized SiC particles (~500nm), micro-sized (<25µm) quasicrystalline alloy particles (hereinafter referred to as “NQX”) and micro-sized Nb particles (~130µm) has been carried out by powder metallurgy routes followed by extrusion or cold rolling. After extrusion, a homogeneous distribution of secondary particles has been obtained with rare interfacial reaction products. The 6061Al/SiC composites exhibit superior mechanical properties than either monolithic alloys or composites reinforced with micro-sized particles with retained ductility while the 6061Al/NQX and 6061Al/Nb composites show limited improvement in tensile strength mainly due to their reinforcement size and poor interfacial bonding. After cold rolling, the evolution in microstructure, texture and strength has been analysed. A typical near β fibre texture with highest intensities near Copper and Brass orientations has been developed for 6061Al/NQX and 6061Al/Nb composites. For 6061Al/SiC composites, a randomized texture with very small grains has achieved due to the presence of the non-deformable SiC particles. Mechanical property tests including microhardness, three-point bending tests and tensile tests have been carried out on cold rolled samples and the results exhibit some level of improvement when compared with as-extruded samples due to work hardening. Finally, the work moves on to the general discussion based on the previous result chapters. The microstructural development related to reinforcement, matrix and interfacial areas during extrusion and cold rolling has been summarised and the correlation between microstructure and mechanical properties has been discussed. The thesis provides a thorough understanding of AlMCs produced by powder metallurgy routes in terms of matrix, reinforcement and processing techniques. It can provide reference to the future development of AlMCs for high strength applications.
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Bester, J. A. "The slurry erosive-corrosive wear of a selection of aliminium alloys, particulate reinforced aluminium metal matrix composites and a selection of steels." Master's thesis, University of Cape Town, 1993. http://hdl.handle.net/11427/18213.
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A range of aluminium alloys and particulate reinforced aluminium metal matrix composites has been tested in an apparatus which simulates the erosive-corrosive action of a slurry. The slurry consisted of silica sand suspended in either distilled water or synthetic mine water. Several steels were also tested in order to clarify certain concepts relating to the synergistic effects of erosion and corrosion. In general both the heat-treatable and non heat-treatable aluminium alloys exhibit lower slurry erosion rates with increasing hardness and work to fracture values. The slurry erosion rates of the aluminium matrix alloys increase with increasing amounts of reinforcement particles. For the steels a good work hardening capacity and/or high hardness values are found to promote good slurry erosion resistance. All the steels exhibit lower slurry erosion rates than the aluminium alloys. A corrosion cell was developed to allow in situ electrochemical measurements to be made. The addition of corrosive ions to the distilled water results in increased material removal rates, increasing by as much as 40% for some of the aluminium alloys and 41%for the 304 stainless steel. The aluminium alloys and the steels which have increased corrosion resistance due to passivity, display poor performance under the slurry erosion-corrosion conditions tested. Paradoxically corrosion resistance was found to have a detrimental effect on the slurry erosion-corrosion resistance of a material.
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Couch, P. D. "Fatigue and fracture of an aluminium-lithium based metal matrix composite at both ambient and elevated temperatures." Thesis, University of Birmingham, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499904.
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Karakas, Mustafa Serdar. "Effect Of Aging On The Mechanical Properties Of Boron Carbide Particle Reinforced Aluminum Metal Matrix Composites." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/2/12608944/index.pdf.
Full textAbstract:
Metal matrix composites (MMCs) of Al - 4 wt.% Cu reinforced with different volumetric fractions of B4C particles were produced by hot pressing. The effect of aging temperature on the age hardening response of the composites was studied and compared with the characteristics exhibited by the matrix alloy. Reinforcement addition was found to considerably affect the age hardening behavior. Detailed transmission electron microscopy and differential scanning calorimetry observations were made to understand the aging response of the composites. The low strain rate and high strain rate deformation behavior of the MMCs were determined utilizing low velocity transverse rupture tests and true armor-piercing steel projectiles, respectively. Increasing the volume fraction of B4C led to a decrease in flexural strength. The flexural strength vs. strain rate plots showed a slight increase in strength followed by a decrease for all samples. The mechanical performance of the composites and the unreinforced alloy were greatly improved by heat treatment. The MMCs were found to be inferior to monolithic ceramics when used as facing plates in armors.
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DeMarco, James P. Jr. "Mechanical characterization and numerical simulation of a light-weight aluminum A359 metal-matrix composite." Master's thesis, University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4933.
Full textAbstract:
Aluminum metal-matrix composites (MMCs) are well positioned to replace steel in numerous manufactured structural components, due to their high strength-to-weight and stiffness ratios. For example, research is currently being conducted in the use of such materials in the construction of tank entry doors, which are currently made of steel and are dangerously heavy for military personnel to lift and close. However, the manufacture of aluminum MMCs is inefficient in many cases due to the loss of material through edge cracking during the hot rolling process which is applied to reduce thick billets of as-cast material to usable sheets. In the current work, mechanical characterization and numerical modeling of as-cast aluminum A359-SiCsubscript p]-30% is employed to determine the properties of the composite and identify their dependence on strain rate and temperature conditions. Tensile and torsion tests were performed at a variety of strain rates and temperatures. Data obtained from tensile tests were used to calibrate the parameters of a material model for the composite. The material model was implemented in the ANSYS finite element software suite, and simulations were performed to test the ability of the model to capture the mechanical response of the composite under simulated tension and torsion tests. A temperature- and strain rate-dependent damage model extended the constitutive model to capture the dependence of material failure on testing or service conditions. Several trends in the mechanical response were identified through analysis of the dependence of experimentally-obtained material properties on temperature and strain rate. The numerical model was found to adequately capture strain rate and temperature dependence of the stress-strain curves in most cases.; Ductility modeling allowed prediction of stress and strain conditions which would lead to rupture, as well as identification of areas of a solid model which are most likely to fail under a given set of environmental and load conditions.ID: 030423478; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.S.M.E.)--University of Central Florida, 2011.; Includes bibliographical references (p. 113-118).
M.S.
Masters
Mechanical, Materials, and Aerospace Engineering
Engineering and Computer Science