EP0346771A1 - Verfahren zur Herstellung von Verbundwerkstoff, insbesondere eine Metallmatrix mit dispergierten Keramikteilchen - Google Patents

Verfahren zur Herstellung von Verbundwerkstoff, insbesondere eine Metallmatrix mit dispergierten Keramikteilchen Download PDF

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Publication number
EP0346771A1
EP0346771A1 EP89110482A EP89110482A EP0346771A1 EP 0346771 A1 EP0346771 A1 EP 0346771A1 EP 89110482 A EP89110482 A EP 89110482A EP 89110482 A EP89110482 A EP 89110482A EP 0346771 A1 EP0346771 A1 EP 0346771A1
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Prior art keywords
dispersates
composite
matrix
metal
alloy
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EP89110482A
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English (en)
French (fr)
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EP0346771B1 (de
Inventor
Christopher K. Knapp
Sjur Vidar Velken
James A. Cornie
Merton C. Flemings
Donald R. Gorsuch
Eric Klier
Andreas Mortensen
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Saint Gobain Abrasives Inc
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Norton Co
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    • 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
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • 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
    • C22C32/0063—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 based on SiC
    • 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
    • C22C1/1005—Pretreatment of the non-metallic additives
    • C22C1/1015—Pretreatment of the non-metallic additives by preparing or treating a non-metallic additive preform
    • C22C1/1021—Pretreatment of the non-metallic additives by preparing or treating a non-metallic additive preform the preform being ceramic
    • 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
    • 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
    • C22C32/0047—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
    • C22C32/0052—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
    • C22C32/0057—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 based on B4C

Definitions

  • This invention relates to solid composite materials, pre­ferably metal-matrix composites (MMC), which comprise a continu­ous metal matrix material having a plurality of separate parti­cles, i.e. dispersates, dispersed throughout the matrix and to methods for making such composites having an extremely uniform dispersion of the dispersates and simultaneously having essen­tially no porosity.
  • MMC metal-matrix composites
  • the invention is particularly directed to metal-matrix composites having ceramic dispersates substantially uniformly distributed throughout the matrix phase.
  • the present invention provides a solution to the problems of excessive poros­ity in the MMC's and excessive clustering of the particulates, which problems have prevented as-cast composites from having pro­perties comparable to powder metallurgically forged or extruded composites.
  • One method of making composites in which a matrix material is obtained from a fluid state is to disperse dispersates in a precursor liquid and then form the composite by solidifying the liquid part, i.e. dispersion medium, of the dispersion.
  • a precursor liquid i.e. dispersion medium
  • U.S. Pat. No. 4,735,656 suggests overcoming the density segregation problem by (i) mixing metal particulates with ceram­ic particulates and then (ii) heating the mixture to a tempera­ture high enough to cause partial melting of the metal (so that it fuses into a dense matrix when cooled) but not so high as to cause the ceramic particulates to float therein.
  • the care re­quired to utilize this process makes the process undesirable for large scale commercial operations. Also process does not in­herently preclude the presence of voids in the final product.
  • Composites having the most desirable properties for many purposes are produced when the dispersates therein are suffic­iently widely dispersed that most of them do not touch another dispersate particle.
  • This class of composites is characterized herein as having "discrete” dispersates or as a “discrete disper­sion.” It has now been found that many of the difficulties in the prior art of making discrete composites can be overcome by using an indirect method of preparation which entails (i) making a concentrated dispersion of dispersates and a precursor to the final matrix in which there is intimate contact between the pre­cursor matrix material and the dispersates and then (ii) dissolv­ing the concentrated dispersate dispersion in additional matrix precursor material.
  • a concentrated dispersion is used to form the more dilute dispersion of the disired composi­tion by mixing it with additional matrix fluid precursor and dis­persing it therein. If the mixing is done while the dispersion medium of the concentrated dispersion is still fluid, this embod­iment is referred to as a "continuous" method. Sometimes, how­ever, it may be more convenient to solidify the dispersion medi­um of the concentrated dispersion producing a "concentrated com­posite" before beginning the mixing step to prepare the finally desired composite. Composites made in this way are denoted as being made by the "concentrated composite" embodiment of the in­vention.
  • the fluid infiltration into the bed may be ac­complished from multiple directions, if desired. Often it is more convenient to omit the evacuation step and infiltrate the dispersate bed only from a single direction while permitting the displaced air to escape through an open part of the bed.
  • infiltration may still be successsfully achieved by applying a pressure to the fluid.
  • the infiltration process general simplyly does separate some of the interparticle contracts between the packed dispersates, the resultant dispersion is more concentrat­ed than the final dispersion made therefrom.
  • the infiltration of the packed porous bed of dispersates is usually performed under minimum suitable conditons of both temperature and pressure.
  • a low temperature any reac­tion between the dispersate powder and the matrix precursor will be minimized.
  • the temperature of the matrix precursor flu­id used should be about 25 to about 200, preferably about 50 to about 175, and most preferably about 75 to about 125°C. above its melting point.
  • the dispersates are preheated to essentially the temperature of the matrix precursor fluid to pre­vent metal cooling or freezing off which otherwise could occur and reduce or prevent the complete infiltration.
  • pressure the use of pressure has been found to be advantageous to reduce/eliminate porosity in the concentrated dispersion but simultaneously increase the cost of performing the infiltration.
  • the pressure used is chosen to balance the level of poros­ity of the concentrated dispersion and the cost. Generally, an overpressure of at least 25 psi will be preferred with still higher overpressures being more preferred as the particle size of the dispersates is reduced. Also to help minimize any porosi­ty due to too low a pressure having been used, it has been found to be desirable to increase the overpressure to about 200 to 300 psi near the end of the infiltration process.
  • wetting agents In order to promote good displacement of interparticle gas­es at relatively low infiltration pressures during the formation of the composites, it has been found beneficial to incorporate known wetting agents to the matrix precursor materials used to form the concentrated dispersion.
  • the specific wetting agents and amounts thereof utilized will normally depend upon the spe­cific matrix material and dispersate and can be determined by routine experimentation. For instance, when preparing a compos­ite of silicon carbide and an aluminum alloy, tin and potassium hexafluorozirconate are preferred wetting agents since they are known to promote the wetting of silicon carbide and can be readi­ly added to the aluminum alloy precursor material.
  • the mixing of the concentrated dispersion with additional precursor fluid is then accomplished in a way that avoids the difficulties with dispersing small particles directly in an open container of fluid, as discussed above.
  • mixing becomes very easy. Portions of the concentrated dispersion can simply be placed atop a second matrix fluid, if the dispersates are denser than the matrix, or covered with the second matrix fluid, if the dispersates are less dense than the matrix.
  • a combination of gravity and stirring then mixes the dispersates into the total amount of fluid matrix precursor.
  • a non-vortex generating mixer will be used to minimize any air entrapment.
  • the mixer must obviously be made of a material which will not react with or degrade the matrix precursor fluid. Suitable such materials will depend upon the particular composition of the composites. For example, with an aluminum alloy matrix, mixers prepared from graphite or steel coated with a nonwetting wash or spray such as carbon, sodium chloride, or mica wash are preferred. In some alloys, Cotronics 902 machinable ceramic from Contronics Co., Brooklyn, NY, may be used.
  • High shear mixing is preferred to disperse any small clus­ters or agglomerates of dispersates remaining from the concen­trated dispersion and also to provide a more uniform distribu­tion of the dispersates in the final composite.
  • the temperature is normally maintained within the range at which the mixtures containing the dispersates exhibit thixotropy so that efficient mixing is achieved while reducing the possibility of dispersate resegregation due to density differences as the mixed material moves away from the mixing zone.
  • a portion of the concentrated composite may be held mechanically below the sur­face of a body of second precursor fluid, maintained at a temper­ature high enough to reliquify at least part of the matrix of the concentrated composite, and portions of the two components of the concentrated composite can be mixed into the second pre­cursor fluid as liquefication occurs.
  • the concen­trated composite can be heated to, and held at, a temperature sufficient for partial liquefication of its matrix, and addition­al fluid precursor added with mixing.
  • the invention provides the first discrete dispersions that are (i) substantially free of pores and (ii) have an essen­tially uniform dispersion of the dispersates.
  • new dispersions and also not more than about 40 volume percent of dispersates and also not more than about 5 volume percent voids, pores and gases are provided herein.
  • a "precursor of a matrix material” refers to any material that can be converted into the desired matrix material by chemi­cal or physical treatment without dislocation of any dispersates contained therein.
  • a liquid alloy or a thermoplastic res­in is a precursor to the solid alloy or resin into which it hard­ens on cooling; or fluid mixtures of polyfunctional isocyanates and polyfunctional alcohols are precursors to the polyurethanes that they form by chemical reaction after mixing; or fluid acryl­ated materials are precursors of the polymer that they form af­ter exposure to an electron beam.
  • “Matrix” is used herein to re­fer to the continuous phase of any dispersion or composite, be it in a fluid or a solid state.
  • the solid composite materials of the present invention are comprised of two primary materials - the matrix and the dispers­ ates.
  • Matrix materials useful in the present invention include metals, metal alloys, and thermoplastic resins. Suitable metals and metal alloys include aluminum, aluminum alloys, magnesium, magnesium alloys, bronze, copper, copper alloys, zinc, and zinc alloys. Suitable thermoplastic resins include polyester polyure­thanes, polyether polyurethanes, and acrylic polymers and copoly­mers.
  • the matrix material is selected from aluminum, aluminum alloys, magnesium, magnesium alloys, and magnesium-alum­inum alloys. Most preferably the matrix material is an aluminum alloy containing less than about 12 w/o, preferably less than a­bout 8 w/o, and most preferably less than about 1.5 w/o silicon.
  • Suitable dispersates for use herein are ceramic materials such as silicon carbide, silicon nitride, aluminum nitride, alum­ina, titania, silica, boron carbide, borides, carbides, sili­cides, diamond and the like. These materials are characterized as having a modulus, strength and wear resistance which are sub­stantially higher than that of the matrix materials.
  • the dispersates are either silicon carbide, silicon nitride, alu­minum nitride, or aluminum oxide.
  • the dispers­ates are silicon carbide.
  • the dispersates irrespective of the particular chemical composition, are used in the form of fine particles, generally having an average particle size of about 0.1 to about 45 microns, preferably about 3 to about 20 microns, and most preferably about 7 to about 15 microns.
  • the concentrated dispersion will generally be prepared to contain as much dispersate as possible. Thus, about 25 to about 85 w/o, preferably about 45 to about 60 w/o, and most preferably about 53 to about 56 w/o dispersates will be used.
  • Some of the most useful applications of this invention are in the manufacture of composites of silicon carbide dispersed in aluminum or magnesium alloys. Such materials are valuable cons­truction materials for applications such as airplane bodies and other components in which a combination of low density, high toughness, and high flexure resistance at temperatures not too far below melting point of the alloy are needed.
  • Alloys of aluminum containing from about 1 to 4% silicon are known to make stronger composites when reinforced with ceram­ic materials such as silicon carbide than do aluminum alloys con­taining less silicon. This is so even though unreinforced sili­con-aluminum alloys containing less than 1% silicon are stronger than those containing more than 1% silicon.
  • the difficulty of making composites with low-silicon aluminum alloys and silicon carbide is believed caused by a reaction between the low-silicon aluminum alloy and the silicon carbide dispersates which pro­duces aluminum carbides.
  • the aluminum carbide formation weakens the matrix/particulate interface and makes SiC a less effective reinforcement material.
  • silica dispersates when silica dispersates are used with a low-sil­icon aluminum alloy they can react with the aluminum to form sil­icon and alumina. And when titania dispersates are utilized to reinforce low-silicon alloys, they can react to from Ti Al and alumina. Similarly, other deleterious reactions can occur with various ceramic and metal combinations, as is known.
  • the difficulties caused by such deleterious interactions between desirable dispersates and either the precursor to the ma­trix material or the matrix material itself, such as occur when silicon carbide dispersates are used to reinforce a low-silicon aluminum, can be overcome with an embodiment of the present in­vention.
  • the deleterious reaction is inhibited sufficiently, or ideally prevented, by coating the dispersate particles with a ma­terial that (i) will not react with either the precursor or the matrix material, but (ii) will produce an adherent coating on the dispersates, and (iii) will promote wetting of the dispers­ates by the matrix precursor.
  • Suitability of particular dispersate coating materials can be determined by routine experimentation by coating particular dispersates, then attempting to infiltrate a packed porous bed thereof with the desired matrix precursor fluid, and if the in­filtration succeeds then attempting to disperse the concentrated dispersion into additional matrix precursor material.
  • suitable coatings for use with low-silicon aluminum alloys include metals, metal oxides, metal nitrides, metal carbides and metal borides.
  • a metal coating such as copper, molybdenum, nickel, zinc, tin, or titanium is used, it is preferably extreme­ly thin, i.e. up to about 2 microns, to minimize any detrimental intermetallic interactions.
  • Metal oxides useful herein include such as silica, alumina, chromia, nickel oxide, copper oxide, mullite, spinels, titania, magnesium silicate, lithium silicate, and the like.
  • Metal nitrides useful herein include silicon ni­tride, titanium nitride, boron nitride, and aluminum nitride.
  • Metal silicon compounds useful herein include molybdenum, copper and titanium silicides.
  • Silicon dioxide which can be formed on silicon carbide by heating in air, is currently preferred, partially because it is particularly convenient to produce by merely heating silicon carbide powder at about 1300°C. for about 30 minutes.
  • Alumina which can conveniently be coated onto silicon carbide particles from a seeded sol to form the coating is also preferred.
  • Such coatings have generally not been found necessary for final composites prepared with magnesium-based alloys, because the formation of deletereous products has not been found to be as extensive, even if the magnesium is alloyed with aluminum.
  • a quartz tube 16 cm in length and with an internal diame­ter of 2.2 cm was coated internally for a distance of about 15 cm with a suspension of colloidal graphite available from Ache­son Colloids, Ltd., Brantford, Ontario, Canada, under the trade name AQUADAG.
  • the container thus formed by the coated tube end and the porous plug was filled with grit F600 green sil­icon carbide to a packing density of about 50 volume %, with the aid of a vibrating table contacting the container.
  • the size distribution of Grit F600 silicon carbide is described fully in publications of the Federation of European Producers of Abras­ives, hereinafter "FEPA"
  • the particular lot of Grit F600 used for this experiment was measured with a Coulter Counter and had 50% of its volume in particles with a size of more than 9.1 mi­crons; 3% of the volume was made up of grits larger than 15.3 microns, 94% of the volume was made up of grits larger than 4.8 microns, and the central 75% of the volume was made up of grits with sizes between 6.2 and 12.2 microns.
  • the central 75% of the volume is defined as the part of the sample excluding the larg­est and the smallest particles that each make up 12.5% of the total volume.
  • the top surface of the packed bed of SiC was covered with a layer of porous alumina paper (Product APA1 from Zircar Pro­ducts, Florida, New York) and this end of the container was then wrapped with aluminum foil.
  • the porous alumina paper is fitted tightly enough to keep the packed bed from falling out when the container is inverted and to serve as a filter to exclude oxides or other unwanted foreign matter when molten metal is later in­ filtrated into the packed bed.
  • the aluminum foil allows the pro­tected end of the container to be immersed in the molten alumi­num alloy without contaminating the contents with a layer of ox­ide that forms spontaneously on molten aluminum alloys. Shortly after immersion, the aluminum foil melts. The amount of alumi­num foil is too small to change the composition of the molten aluminum alloy to any significant extent.
  • the wrapped container with its packed bed was then placed in a gas tight desiccator that was evacuated to a pressure of no more than 0.01 bar and then backfilled with argon.
  • the contain­er as thus prepared was positioned within an apparatus illustrat­ed in Figure 1.
  • the quartz tube 1 now has the alumina paper 5 at the bottom of the packed bed 4, with the porous fireclay plug 3 and the support road 2 on top.
  • the tube 1 is connected via a gas tight fitting 6 to a channel 7 that allows the input or exit of gas from the space above the porous plug independently of the space 8 in the upper part of the apparatus.
  • the tube with its packed bed was immersed as shown in Fig­ure 1 in a bath of molten A357 aluminum alloy (which contains about 7% silicon) 9, with a melting point of 610°C, maintained within a graphite crucible 10 at a temperature of 700°C by a conventional heating element 11.
  • the crucible and heater are within a gas tight space defined by container 12, which is pro­tected from the heat of the heating element 11 by insulation 13.
  • Space 8 was initially filled with argon gas at atmospheric pres­sure. After preheating the tube containing the packed bed for 5 minutes, at which point the thermocouple 15 showed that the tem­perature of the molten metal 9 had recovered to the desired val­ue of 700°C.
  • the pressure within the furnace above the layer of molten alloy was increased at the rate of 1.36 bar/min by admission of additional argon gas through input channel 14. This pressure caused the fluid alloy to flow through the packed bed from the bottom, displacing gas from the top of the bed through the porous plug into the separate channel 7.
  • Particles of grit F600 silicon carbide were put into the bottom of a steel crucible to give a packed bed with about 50 v/o SiC.
  • a sufficient amount of molten alloy of 90% Mg - 10% Al to infiltrate the entire packed bed was poured over the bed, and the crucible with its contents placed inside a pressurizable fur­nace maintained at 700°C. Compressed argon was then admitted to the furnace until the pressure reached 34 bars. This was suffi­cient to cause the molten alloy to impregnate all of the packed bed except for a small pocket at the bottom into which the air originally present in the packed bed had been displaced.
  • a portion of the fully impregnated concentrated composite prepared as described immediately above was softened at 700°C. and mixed with an additonal amount of molten 90% Mg - 10% Al al­loy chosen to result in a final composite with 20 v/o SiC.
  • Mix­ing was initially accomplished with a hand-held stirring rod un­til the concentrated composite was sufficiently low in apparent viscosity to allow effective mechanical stirring.
  • Mixing was then continued with a double helical stirrer operated at 400 rev­olutions per minute. This avoided entraining gas through vortex formation.
  • a semi-solid slur­ry that could be cast into a mold resulted.
  • the material was then cast and allowed to solidify. A well dispersed final com­posite was formed.
  • the concentrated composite was mixed with additional molt­en matrix alloy in a special container, under an argon atmo­sphere, using an agitator similar to a turbine moving at 2,000 - 3,000 revolutions per minute.
  • a system of baffles in the con­tainer prevented any significant gas entrapment during mixing.
  • the dispersion was mixed for about five minutes at a temperature of about 700°C.
  • the stirrer was then immediately removed and the dispersion promptly cast in a copper chill mold about 9 mm deep.
  • a well-dispersed composite with about 15 v/o dispersates resulted.
  • This example illustrates application of the invention to continuous casting and is accomplished with apparatus shown in cross section in Figure 4.
  • Molten alloy 100 and concentrated composite are continuously fed into a chamber 102 maintained at a temperature that will keep the mixture at least partially flu­id.
  • the mixture is pumped and blended by a ro­tor 103 into a mixing region 104, where it experiences vigorous agitation.
  • the high shear rates in region 104 are achieved in a narrow gap 104 between chamber wall 105 sand a rotor 106.
  • Both the chamber wall and the rotor have surfaces including a conic frustrum with the same taper angle, so that the gap width, and correspondingly the rate of shear, can be adjusted by relative vertical displacement between the rotor and the chamber wall.
  • the well dispersed dispersion exits in region 107 and can be fed into a crucible for solidification processing, continuously cast into a billet, or the like.
  • the concentrated composite itself could be rotated vigorously in a bath of molten alloy so that portions of the concentrated composite are peeled off at the interface as the matrix of the concentrated composite softens under the influ­ence of the higher temperature of the bath of molten alloy.
  • FIG. 1 illustrates another continuous method embodi­ment of the invention and may be understood with the aid of Fig­ure 5, a cross sectional view of apparatus useful for the inven­tion.
  • a solid chamber 201 capable of withstanding the pressures involved is provided with conventional means for maintaining var­ious temperatures in different regions in its interior and con­tains two inlets 202 and 203 and an outlet 204.
  • molten metal 205 is supplied under pressure.
  • dis­persates 206 are supplied at an appropriate rate and also under pressure by means of a ram, screw feeder, or other appropriate device known to those skilled in the art.
  • chamber 201 is kept at a temperature that will maintain molten metal in regions 205 and 207 and at a temperature too low to melt the metal used at the top of region 206, which consti­tutes a packed bed of dispersates.
  • the flow of dispersates from zone 203 is maintained in a downward direction by mechanical pressure exerted against the packed bed of dispersates, but this does not prevent metal from filling the interparticle space in the packed bed of dispersates in the lower part of the entry re­gion for dispersates, where the temperature is sufficiently high to keep the metal molten.
  • a zone of concentrated composite according to this invention forms in region 207, but upward pene­tration of the metal is limited by its solidification in the up­per part of the inlet 203, creating a more or less distinct boundary between region 207 containing concentrated composite and region 206 with dispersates and gas only.
  • the flow rate of the metal is accelerat­ed by a constriction caused by a bulge 208 in the chamber wall.
  • the concentrated composite is continuously entrained downstream by the rapidly flowing molten metal and it is sheared and dispersed into the flowing metal.
  • a re­gion 209 of substantially homogeneous and nonporous dispersion is obtained. This dispersion can be continuously cast from the outlet 204 to yield a solid continous billet 210 of the finally desired composite.
  • the volume fractions of metal matrix and dis­persates are controlled by regulating the relative feeding rates of dispersates and molten metal at their inlets 203 and 202 re­spectively.
  • Example 2 This was performed in the same manner as Example 1, except that the SiC particulates used were a mixture of equal volumes of FEPA Grit F400, Grit F500, and Grit F600.
  • the Grit F600 had the same size distribution as in Example 1.
  • the Grit F500 mater­ial had 3% of its volume in particles larger than 22.5 microns, 50% of its volume in particles larger than 13.7 microns, 94% of its volume in particles larger than 8.7 microns, and the central 75% of its volume in particles with sizes between 10.6 and 17.7 microns, all as measured by a Coulter Counter.
  • the Grit F400, material had 3% of its vol­ume in particles larger than 25 microns, 50% of its volume in particles larger than 17 microns, 94% of its volume in particles larger than 12 microns, and the central 75% of its volume in par­ticles with sizes between 13 and 20. 5 microns.
  • the central 75% of the volume of the mixture had particles between 7.8 and 19 microns, 3% of the volume of the mixture was in particles smaller than 5.2 microns, and 94% of the volume of the mixture was in particles larger than 21 microns.
  • the final composite produced had an apparently uniform distribution of all particle sizes of SiC within the matrix when examined in cross section.
  • Example 2 This was the same as Example 1, except that the dispers­ates used were boron carbide rather than silicon carbide. Good redistribution of the concentrated composite was obtained in the final composite.
  • Example 2 This was performed in the same as Example 1, except that (i) 100 g of concentrated composite and 215 g of additional A357 alloy were used, to give a 15 v/o composite; (ii) the melt temp­erature during the mixing of the concentrated composite into the additional molten alloy was only 670°C rather than 700°C; and fi­nal stirring was for only 2.5 minutes instead of five. The dif­ference in temperature considerably increased the apparent vis­cosity during the mixing of the concentrated composite with addi­tional matrix material, and some large air pores were introduced during the stirring and preserved in the final composite. There­fore, even though the SiC dispersates were again well dispersed within the final composite, the results were less preferable than for Example 1.
  • Example 2 This was performed in the same way as Example 1, except that (i) the alloy used was Type 6061 alloy rather than the A357 and (ii) 100 g of concentrated composite and 149 g of additonal molten alloy were used in the final mixing step.
  • Type 6061 alloy contains 0.6% Si, 1.0% Mg, 0.3% Mn, and 0.2% Cr, with the balance aluminum. Presumably because of the very low silicon content, the dispersion of the concentrated com­posite within the final composite was not nearly so good as in Example 1.
  • a micrograph of a cross section of the final compos­ite produced in this example is shown in Figure 6.
  • Example 14 This was performed in the same way as Example 14, except that the alloy used was 10% Si - 90% Al. The result contrasted sharply with that of Example 14, in that the distribution of the SiC dispersates within the final composite was very uniform.
  • Example 14 This was performed in the same way as Example 14, except that the alloy used contained 99.9% aluminum.
  • the dispersion of silicon carbide in the final composite was less uniform than that achieved in Example 14.
  • Example 2 This was the same as Example 1, except that the SiC partic­ulates, before forming the concentrated composite, were coated with alumina in the following manner: a boehmite sol at 10 w/o total solids containing 0.15 w/o of fine alpha alumina seeds, prepared in a state of incipient gellation as described in de­tail in U.S. Patent 4,623,364 was prepared. One liter of this sol was mixed with one kilogram of FEPA Grit 600 SiC, and the mixture then pumped through a NIRO spray drier, which caused the SiC to be coated with an apparently uniform coating of dried alumina gel when examined by as scanning electron microscope.
  • a boehmite sol at 10 w/o total solids containing 0.15 w/o of fine alpha alumina seeds prepared in a state of incipient gellation as described in de­tail in U.S. Patent 4,623,364 was prepared.
  • One liter of this sol was mixed with one kilogram of FEPA Grit 600 SiC
  • the coated particulate was then heated at 1200°C for thirty min­utes to convert the alumina gel to alpha alumina. Conversion was confirmed by x-ray diffraction analysis that showed alpha SiC and alpha alumina as the only phases present.
  • the final composite prepared in this Example showed an ex­cellent uniformity of dispersion of the SiC within the matrix.
  • SiC was coated with Cr metal by an evaporation-condensa­tion process to 29%.
  • A357 and Al 99.9 were made using quartz tubes 20 cm. long and .5 cm. ID.
  • the temperature of the infiltrating aluminum was varied between 700°C and 800°C, and the pressure varied up to 400 psi. In both cases infiltration was negligible. It is believed that the chrome metal was dissolved by the molten aluminum producing an aluminum chrome alloy. Small additions of chrome to aluminum significantly raise the melting temperature, thus freezing the metal front before infiltration can occur. Thus chrome metal is not a useful coating material.
  • This powder was pack­ed and infiltrated with A357 as in Example 1 using a pressure of 375 psi and a temperature of 750°C. 89 g of this master compos­ite was heated to 850°C with 209g of A357 to give a final compo­sition of 14 %. After 2 1/2 hours, the master composite pieces had not yet broken up; thus little dispersion occured.
  • a master alloy was prepared using A357 and SiC coated with chrome to 3.5 wt% and calcined as in Comparative Example B. In this case, however, the Cr was completely oxidized to chromia. The infiltration occured at 750°C with 400 psi. 94.9 g of this concentrated dispersion sample was dispersed into 235 g of A357 to give a composite of 13.4 wt% SiC. This took 15 minutes at 850°C. Micrographs indicate a good dispersion with a few clumps of master alloy remaining which can be broken down with improved stirring. In this case the chrome oxide coating prevented any reaction between the aluminum metal and the SiC to allow disper­sion of the master alloy to occur. The absence of any chrome me­tal in the coating also prevents the melting point of the alloy from rising which had ben found to prevent dispersions of the master composite in Comparative Examples A and B.
  • a coating of Si3N4 on SiC particulate was produced by heating SiC in flowing nitrogen gas to 1425°C.
  • a master compos­ite was produced as in Example #1 using A357 at 300 psi and 725° C. 75 g of this master composite was stirred into 192 g of A357 as in Example 20 to give a final fraction of 13.1% SiC. Disper­sion occured easily. Micrographs of the final composite indi­cate good dispersion of the coated SiC particulate without any noticeable reaction products being formed between the metal ma­trix and the coated SiC dispersates.
  • SiC was coated to 8.3% Ni metal using a NiB electroless plating solution.
  • Infiltration was accomplished using quartz tubes, as in Example #19, with the A357 at 725°C and applying a pressure of 200 psi.
  • 9.3 g of this master alloy was dispersed into 57.9 g of A357 using a small porcelain crucible and a graph­ite stirring rod. Furnace temperature was set to 800°C.
  • the master composite did not disperse evenly, presumably due to ni­ckel-silicon alloy formation, thus indicating that a nickel me­tal coating is not suitable with this aluminum alloy.
  • Comparative Example C The procedure of Comparative Example C was repeated reduc­ing the nickel content on the dispersates to 2% and using Al 99.9 as the matrix material and in both the infiltration and the dispersion. A good dispersion results.
  • SiC was given a total 9.5 % coating of a chromia-alumina solid solution. This coating was produced by mixing equal weights of SiC and a 30 % solids solgel of Cr(NO3)3-9H2O and Al2O3-H2O. The resulting slurry was dried to a powder and fired at 1250°C to remove structurel water in the coating ma­terials and to convert the nitrate to an oxide.
  • This SiC was in­filtrated with A357 as in Example 1 using a temperature of 725° C. and a pressure of 160 psi. 5.8 g of this master alloy was then stirred into 60.7 g of A357 to give a composite having 4.0% SiC. Dispersion was good.
  • a 6% molbdenum coating was placed on silicon carbide parti­cles by mixing coarse molybdenum powder with F600 SiC in an ap­propriate weight ration and heating in a vacuum furnace to evap­orate the molybdenum and redeposit it on the SiC particles.
  • the coated particles were then processed as in Example 1 with A357 alloy to form a concentrated dispersion thereof containing 54% dispersates.
  • the concentrated dispersion was then stirred into further A357. Good break-up of the concentrated dispersion is observed and a uniform final composite is produced.
  • Example 24 The procedure of Example 24 was repeated to produce a 6% titanium metal coating on silicon carbide dispersates, to use those dispersates to prepare a concentrated dispersion, and to use the concentrated dispersion to prepare a final uniform dis­persion. A good dispersion resulted.
  • Example 25 The procedure of Example 25 was repeated to produce the ti­tanium metal coated silicon carbide dispersates and then the ti­tanium coating was oxidized to converted it to titania. Infiltra­tion with A357 at a pressure of 160 psi was barely adequate to produce a void-free concentrated dispersion, but when repeated at 300 psi the process proceeded smoothly. Good final disper­sions were produced in each case.
  • a titanium nitride coating was placed on silicon carbide dispersates by (i) forming a silica and carbon diffusion layer by calcining the SiC in air at 1100°C., (ii) coating titanium metal thereon by a pack diffusion process, and then (iii) ni­triding at 925 - 1025°C. to convert the metallic Ti to TiN.
  • the resulting dispersates were readily infiltrated with pure alumi­num to form a concentrated dispersion which was stirred into fur­ther pure aluminum to produce a well- dispersed final composite product.

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EP89110482A 1988-06-17 1989-06-09 Verfahren zur Herstellung von Verbundwerkstoff, insbesondere eine Metallmatrix mit dispergierten Keramikteilchen Expired - Lifetime EP0346771B1 (de)

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WO1991017276A2 (en) * 1990-05-09 1991-11-14 Lanxide Technology Company, Lp Filler materials for metal matrix composites
TR25639A (tr) * 1990-04-12 1993-07-01 Alcan Gmbh KOMPOZIT DÖKüM PROSESI
EP0577381A1 (de) * 1992-07-02 1994-01-05 Toyota Jidosha Kabushiki Kaisha Verfahren zur Herstellung eines metallischen Verbundwerkstoffes enthaltend dispergierte Metallkarbid
US5441697A (en) * 1992-08-06 1995-08-15 Toyota Jidosha Kabushiki Kaisha Method of producing TiC whiskers and metallic composites reinforced by TiC whiskers
EP0671478A3 (de) * 1990-07-26 1995-11-29 Alcan Int Ltd Gegossenes Verbundmaterial.
US6635357B2 (en) * 2002-02-28 2003-10-21 Vladimir S. Moxson Bulletproof lightweight metal matrix macrocomposites with controlled structure and manufacture the same
EP2954083A4 (de) * 2013-02-11 2016-10-26 Nat Res Council Canada Metallmatrixverbundmaterial und verfahren zur bildung

Families Citing this family (2)

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US5299724A (en) * 1990-07-13 1994-04-05 Alcan International Limited Apparatus and process for casting metal matrix composite materials
DE19619138C2 (de) * 1996-05-11 2002-04-18 Degussa Verfahren zur Herstellung von vinylierten Silicium-organischen Verbindungen

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EP0104682A1 (de) * 1982-08-27 1984-04-04 The Dow Chemical Company Verfahren zum Einbringen unlöslicher Stoffe in flüssige oder teilweise flüssige Metalle
EP0150519A1 (de) * 1984-01-30 1985-08-07 Nederlandse Organisatie voor toegepast-natuurwetenschappelijk onderzoek TNO Verfahren zur Herstellung eines Verbundmaterialgegenstandes bestehend aus einem Körper von porigem Material und einem anderen, diesen Körper infiltrierenden Material
EP0256600A2 (de) * 1986-08-19 1988-02-24 NUOVA SAMIM S.p.A. Verbundmaterial einer Zn-Al-Legierung, die mit Silicium-Karbid-Pulver verfestigt ist
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EP0104682A1 (de) * 1982-08-27 1984-04-04 The Dow Chemical Company Verfahren zum Einbringen unlöslicher Stoffe in flüssige oder teilweise flüssige Metalle
EP0150519A1 (de) * 1984-01-30 1985-08-07 Nederlandse Organisatie voor toegepast-natuurwetenschappelijk onderzoek TNO Verfahren zur Herstellung eines Verbundmaterialgegenstandes bestehend aus einem Körper von porigem Material und einem anderen, diesen Körper infiltrierenden Material
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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
TR25639A (tr) * 1990-04-12 1993-07-01 Alcan Gmbh KOMPOZIT DÖKüM PROSESI
US5381850A (en) * 1990-04-12 1995-01-17 Alcan Deutschland Gmbh Composite casting process
WO1991017276A2 (en) * 1990-05-09 1991-11-14 Lanxide Technology Company, Lp Filler materials for metal matrix composites
WO1991017276A3 (en) * 1990-05-09 1991-12-26 Lanxide Technology Co Ltd Filler materials for metal matrix composites
EP0671478A3 (de) * 1990-07-26 1995-11-29 Alcan Int Ltd Gegossenes Verbundmaterial.
EP0577381A1 (de) * 1992-07-02 1994-01-05 Toyota Jidosha Kabushiki Kaisha Verfahren zur Herstellung eines metallischen Verbundwerkstoffes enthaltend dispergierte Metallkarbid
US5336291A (en) * 1992-07-02 1994-08-09 Toyota Jidosha Kabushiki Kaisha Method of production of a metallic composite material incorporating metal carbide particles dispersed therein
US5441697A (en) * 1992-08-06 1995-08-15 Toyota Jidosha Kabushiki Kaisha Method of producing TiC whiskers and metallic composites reinforced by TiC whiskers
US6635357B2 (en) * 2002-02-28 2003-10-21 Vladimir S. Moxson Bulletproof lightweight metal matrix macrocomposites with controlled structure and manufacture the same
EP2954083A4 (de) * 2013-02-11 2016-10-26 Nat Res Council Canada Metallmatrixverbundmaterial und verfahren zur bildung
US9945012B2 (en) 2013-02-11 2018-04-17 National Research Council Of Canada Metal matrix composite and method of forming

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DE68918990D1 (de) 1994-12-01
EP0346771B1 (de) 1994-10-26
NO174007B (no) 1993-11-22
NO174007C (no) 1994-03-02
DK297289A (da) 1989-12-18
BR8902947A (pt) 1990-02-06
NO892404D0 (no) 1989-06-12
DE68918990T2 (de) 1995-07-27
KR910001078A (ko) 1991-01-30
ATE113317T1 (de) 1994-11-15
AU616275B2 (en) 1991-10-24

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