Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
  • C22C21/08—Alloys based on aluminium with magnesium as the next major constituent with silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/10—Alloys containing non-metals
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/10—Alloys containing non-metals
  • C22C1/1036—Alloys containing non-metals starting from a melt
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D25/00—Special casting characterised by the nature of the product
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/10—Alloys containing non-metals
  • C22C1/1036—Alloys containing non-metals starting from a melt
  • C22C1/1068—Making hard metals based on borides, carbides, nitrides, oxides or silicides
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
  • C22C32/001—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides
  • C22C32/0015—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides with only single oxides as main non-metallic constituents
  • C22C32/0036—Matrix based on Al, Mg, Be or alloys thereof
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
  • C22C32/0047—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with carbides, nitrides, borides or silicides as the main non-metallic constituents
  • C22C32/0052—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with carbides, nitrides, borides or silicides as the main non-metallic constituents only carbides
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
  • C22C32/0047—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with carbides, nitrides, borides or silicides as the main non-metallic constituents
  • C22C32/0073—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with carbides, nitrides, borides or silicides as the main non-metallic constituents only borides

Definitions

• the present invention relates to metal matrix composites.
• the present invention envisages a reinforced Aluminum composites and a process for producing the same.
• pneumatically used in the specification means a process (function/operation) carried out using air, gas such as a carrier/inert gas or a gaseous mixture.
• a metal matrix composite is a composite material with at least two constituent parts, one being a metal and the other material being a different non metallic material such as a ceramic or inorganic compound.
• Metal matrix composites are tailor made material comprising a reinforcing material dispersed in a metal matrix.
• the reinforcing material can be synthesized externally and added to the metal matrix or else prepared in-situ in the metal.
• One particular class of MMC that have gained more interest in the recent times is particulate reinforced aluminum matrix composites, prepared by in-situ techniques. These composites have superior mechanical properties compared to the aluminum matrix and have applications in transportation, electronics and recreational products.
• US 4,772, 452 discloses a process for TiC reinforced aluminum matrix composites wherein the aluminum metal, titanium bearing compound and the carbide, all provided in the powder form are pre-mixed, compacted and further heated at a reaction temperature approximating melting point of the aluminum to produce the composite.
• US 6,843,865 discloses a process for TiC reinforced aluminum matrix composites wherein the mixture of aluminum and titanium metals in its molten form is reacted with a halide of carbon to produce the composite. The reaction is carried out under vigorous mechanical stirring.
• US 4,748, 001 discloses a process for TiC reinforced aluminum matrix composites wherein the carbon powder preheated to 700°C is added to the molten mixture of aluminum and titanium metals and the melt is stirred vigorously at high temperature and additional processing is carried out at a very high temperature (1100 to 1400°C) to produce the desired composite.
• the melt is agitated by mechanical stirring.
• Main object of the present invention is to prepare aluminum composites with fine and uniform distribution of the particulate.
• Another object of the present invention is to provide aluminum composites with improved mechanical properties.
• Yet another object of the invention is to provide a cost effective process for preparing aluminum composites.
• a process for preparing particulate aluminum matrix nano-composites comprising the following steps: a) injecting a mixture comprising (i) at least one metal bearing compound selected from the group consisting of titanium compounds, vanadium compounds and zirconium compounds , and (ii) at least one non-metal bearing compound selected from the group containing carbon bearing compounds, boron bearing compounds and oxygen bearing compounds into molten aluminum metal maintained at a temperature in the range of 750°C to 1200°C to obtain a melt;
• the injecting step is carried out such that at least one of the compounds in the mixture is injected pneumatically.
• the injecting step is carried out pneumatically using pressurized carrier gas.
• At least one of the compounds in the mixture in step a) is pneumatically injected into the molten aluminum through a feeder attached to a submersible lance, said lance being immersed in the molten aluminum metal.
• the melt is agitated with a carrier gas.
• the melt is agitated with the carrier gas over a period of 5 to 20 minutes.
• the carrier gas is selected from the group consisting of argon and nitrogen.
• the temperature in the step a) to step b) is maintained in the range of 850°C to 1000°C.
• the compound in step a) is selected from the group consisting of potassium titanium fluoride, titanium oxide, titanium diboride,.
• the compound is titanium compound selected from the group consisting of potassium titanium fluoride and titanium oxide.
• the titanium compound is in the powder form.
• the carbon is selected form the group consisting of graphite powder, carbon-dioxide and methane gas.
• the oxygen is selected from the group consisting of oxygen gas, silica, alumina, zinc oxide and cuprous oxide.
• the particulate aluminum matrix nano-composite as formed contains up to 15% titanium carbide composite.
• the particulate aluminum matrix nano- composite further comprises at least one alloying metal selected from the group consisting of magnesium, copper, zinc and silicon.
• Fig 1 represents XRD overlay of samples prepared according to present invention and the conventional route.
• Fig 2 represents Scanning electron micrographs of prepared according to present invention and the conventional route.
• Fig 3 represents Tensile curve of cast aluminum sample and composite made by present invention
• Fig 4 represents Photographs of samples produced by (a) method of present invention and (b) conventional stir casting method.
• Fig 5 represents Optical micrograph of sample prepared by method of present invention employing carbon dioxide as source of carbon.
• Fig 6 represents Aging curve for composite sample prepared by method of this invention.
• Fig 7 represents Extruded composite samples.
• Fig 8 represents Forged composite samples.
• Metal matrix composites are tailor made material consisting a reinforcing material dispersed in a metal matrix.
• the matrix is a monolithic material into which the reinforcement is embedded.
• the reinforcement is provided to improve physical properties such as wear resistance, friction coefficient, or thermal conductivity of the metal.
• MMC Various methods are used to prepare MMC such as i) Solid state method, where powdered metal and reinforcement material are mixed and then bonded through a process of compaction, degassing, and thermo-mechanical treatment, ii) Liquid state method wherein reinforcement material is stirred into the molten metal and allowed to solidify, iii) A chemical reaction between the reactants to form reinforcement material in-situ in metal matrix, iv) Vapor deposition wherein the fiber is passed through a thick cloud of vaporized metal, coating it.
• Solid state method where powdered metal and reinforcement material are mixed and then bonded through a process of compaction, degassing, and thermo-mechanical treatment
• Liquid state method wherein reinforcement material is stirred into the molten metal and allowed to solidify
• a chemical reaction between the reactants to form reinforcement material in-situ in metal matrix iv) Vapor deposition wherein the fiber is passed through a thick cloud of vaporized metal, coating it.
• Aluminum Matrix Composites are manufactured by the fabrication methods such as Powder metallurgy (sintering), Stir casting and Infiltration. Usually the reinforcement of Aluminum Matrix Composites results in high strength, high stiffness (modulus of elasticity), Low density, High thermal conductivity and excellent abrasion resistance of the reinforced metal compared to properties of pure metal.
• Aluminum Matrix Composites are used for manufacturing automotive parts (pistons, pushrods, brake components), brake rotors for high speed trains, bicycles, golf clubs, electronic substrates, cars for high voltage electrical cables.
• the present invention provides a process for in-situ reinforced aluminum matrix composite.
• the aluminum matrix composite is reinforced with at least one compound obtained by the reaction of a metal bearing compound selected from the group consisting of Titanium compounds, Vanadium compounds, Zirconium compounds, and a non-metal bearing compound selected from the group consisting of carbon bearing compounds, boron bearing compounds and oxygen bearing compounds, wherein the preferred reinforcing compound is Titanium carbide.
• TiC particulate is prepared in-situ by injecting titanium bearing compound and a carbon bearing compound into the molten aluminum.
• the Titanium compound is selected from the group consisting of Potassium titanium fluoride, titanium boride and titanium oxide.
• a pressurized powder injection lance is used to inject the ingredients in the molten aluminum metal.
• Titanium bearing compound e.g. Potassium titanium fluoride, titanium oxide
• Carbon can be added either as graphite powder mixed with titanium bearing salt or in the form of C0 2 /methane gas.
• An inert or reactive gas acts as the powder carrier and disperses the powder within the melt. The gas also agitates the melt to ensure intimate mixing, which enhances the reaction kinetics and lowers the processing temperature (750-1200°C) and time (5 to 60 min). The process thus avoids mechanical stirring which may lead to irregular particulate size. Improvement is also observed in the homogeneity, of mechanical properties, e.g.
• hardness variation is ⁇ 5% within the casting.
• the present invention allows higher amount of reinforcement to be introduced in the melt (up to 15%), without compromising casting integrity.
• Composites prepared by this process have a finer and more uniform distribution compared to those prepared by conventional route of mechanical stirring. Therefore for the same volume fraction of particles, composites according to the invention have superior mechanical properties.
• Fig 1 shows the X-ray diffraction pattern of the composite with peaks corresponding to aluminum, TiC and minor Al 3 Ti phases.
• Fig 2a shows Scanning Electron Microscope analysis showing a very fine and uniform distribution of equi-axed particles of A1 4 C 3 and TiC. A few plates of A13Ti are also found to be present.
• samples prepared by stir casting mechanical stirring
• Sample prepared by method of present invention 101 were produced under identical conditions i.e. 900°C and 30 minutes reaction time.
• About 15 hardness readings were taken on the longitudinal section of the casting and analyzed statistically.
• Vicker's hardness was measured to be 60.5 +/- 1.1, while for the casting made using graphite stirrer the hardness was 65.1+/- 1.7. This shows that that casting made from the present invention leads to more homogenous casting compared to stir casting method
• Metal matrix composites were made as described in example 1.
• One Sample was prepared using coarse K2TiF6 powder having d 90 of 300 micron while another sample was prepared using ground and sieved K2TiF6 powder having d 90 of 68 micron. Hardness of both the samples was measured to be 51 Hv.
• Composite sample generally represented by numeral 103 was prepared by the method of the present invention as described in Example 1. 12 kg of aluminum was melt to 900°C and to the molten aluminum, a mixture of K2TiF6 and carbon powder was added through a screw feeder using argon as the carrier gas. The total addition corresponds to nominal addition of 10 % of TiC volume fraction. The total batch time for the reaction was 20 minutes. After completion of the reaction, dross was removed from the crucible and skimmed melt was poured into a sand mould to produce billets. Fig 4a shows the photograph of the defect free cast billet.
• Another sample was prepared by the conventional stir casting method by melting 500 gms of aluminum to 900°C. A mixture of 495g of K2TiF6 and 22 g of carbon powders were mixed and added to the melt while stirring with graphite stirrer. The reaction was completed in 20 minutes. Due to high viscosity of the melt, skimming operation could not be carried out properly and some dross was left within the melt. The melt was poured in a cast iron mould. Fig 4b shows a photograph of the casting .
• Aluminum composite sample generally represented by numeral 104 was prepared by melting 530gms of aluminum in a SiC crucible at 950C. 113 g of K2TiF6 powder was added to the melt and stirred manually using an alumina rod. C02 gas was bubbled through the molten mixture for 10 minutes through an alumina lance submerged in the melt. The crucible was then removed from the furnace, dross was skimmed from the top of the melt and melt poured in cast iron moulds. XRD analysis revealed the formation of TiC precipitates in the casting and hardness was measured to be 48.2 Hv. Optical micrograph of the sample is shown in Fig 5.
• a melt comprising of aluminum and K2TiF6 was bubbled with a mixture of CO2/N2 to produce Al-AlN-TiC composites.
• air was used as carrier gas instead of argon in Example 1 to produce Al-AlN-TiC composites.
• a Composite sample, generally represented by numeral 105 was prepared using the method described in example 1. Additional alloying additions of 0.5% Mg and 0.8% Si were made before pouring the composite in moulds. Sample test samples were prepared from the cast composite. The test samples were solutionized at 550°C for 1 h and quenched in water. Solutionized samples were then heat treated at 170°C for different duration and hardness taken. The aging curve is shown in Fig
• a number of composite samples were prepared by the method described in example 1.
• the cast samples were machined into billet form and extruded in the temperature range of 400 to 550C in a die to form extruded sections like rod and I- beam.
• Fig 7 shows the extruded products without any visual surface defects.
• Some of the other samples were forged after preheating to 450C and are shown in Fig 8. Table 1
• Hardness of the composite prepared in accordance with the present invention was found to be 59 Hv5 compared to 44 Hv5 for Al-Si matrix using conventional technique. Hardness of composites prepared by mechanical stirring under similar conditions have hardness of 30 Hv5. Elastic modulus of the cast composite was measured from tensile tests to be 90 GPa compared to 69 GPa for pure aluminum. Small pieces were cut from the cast ingot and hot forged at 450°C. These samples showed no signs of cracking during hot forging.

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• 2011
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