Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
  • B22D27/20—Measures not previously mentioned for influencing the grain structure or texture; Selection of compositions therefor
• • 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
  • C22C1/00—Making non-ferrous alloys
  • C22C1/10—Alloys containing non-metals
  • C22C1/1036—Alloys containing non-metals starting from a melt
  • C22C1/1047—Alloys containing non-metals starting from a melt by mixing and casting liquid metal matrix composites
• • 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

Definitions

• This invention relates to the preparation of cast composite materials having matrix alloys that do not readily wet the reinforcement particles, and to cast metal-matrix composite materials, particularly composites having a matrix alloy tailored to avoid the formation of harmful intermetallic phases.
• Cast composite materials are conventionally formed by melting a matrix alloy in a reactor and then adding particles. The mixture is vigorously mixed to encourage wetting of the matrix alloy to the particles, and after a suitable mixing time the mixture is cast into molds or forms. The mixing is conducted while minimizing the introduction of gas into the mixture.
• the cast composite materials have fully wetted particles, few voids, and a generally uniformly mixed structure. Complete wetting is necessary to realize the full composite strength and other mechanical properties.
• the particles can be modified with special coatings, but the coating operation can significantly raise the cost of the particles and the composite material.
• Small amounts of reactive gases can be introduced into the mixing chamber, but the improved wetting may only be achieved at the cost of increased porosity in the cast composite material.
• Special reactive alloying ingredients can be added to the melt, but these are often expensive and may have adverse consequences in the production of undesired minor phases in the cast composite material.
• Another approach is to raise the temperature at which the mixing to achieve wetting is accomplished, but increased temperature may also result in the acceleration of the production of deleterious minor phases where such phases are thermodynamically favored but inetically slow in forming at lower temperatures.
• cast composite materials are prepared by a supplier and cast into ingots at the supplier's plant. The cast ingots are transported to a commercial foundry, where they are remelted and cast to the final shape required by the customer.
• This foundry remelt approach is commonplace throughout industry for the processing of conventional aluminum alloys, and the introduction of aluminum-based cast composite materials into many applications is practical only where they can conform to this approach.
• Experience has shown that, with the proper mixing technique, a wide variety of cast composite materials can be mixed by the suppliers. In the mixing step, the maximum temperature to which the molten composite may be heated is normally limited to avoid the production of unwanted reaction products between the matrix alloying elements and the reinforcement particles.
• present foundry techniques usually call for the melting of large masses of the casting alloy to reach a stable temperature distribution, and casting articles from the large melted mass.
• the remelted material may remain at elevated temperature for extended periods of time, such as up to 24 hours, before casting.
• the castability of the composite material may degrade, so that a composite material may be much less castable after such a holding period than if cast immediately upon remelting. It is important that the composite material be castable by such commercial practices that have been long established, to accelerate the acceptance of the composite material by foundrymen.
• aluminum-7 weight percent silicon alloys have been used in industry for years as remelt alloys, because the alloy has good fluidity and acceptable mechanical properties after casting.
• a satisfactory composite material of, for example, 15 volume percent of silicon carbide particles in an aluminum-7 weight percent silicon alloy may be prepared and cast by the supplier with a maximum temperature of 685"C in the mixing process. Ingots of this alloy are furnished to a foundry remelter, who remelts the ingots and holds the molten composite at a conventional remelt temperature of about 788°C for 8 hours before casting.
• the molten composite material casts very poorly, has low fluidity, and results in unacceptable product. The composite material is therefore rejected for the particular application, even though it might otherwise provide important benefits to the final product.
• One feature of the present invention provides a process modification that permits the production of many cast composite material particle/matrix alloy compositions that are difficult to prepare because the matrix alloy does not wet the particles. No new alloying ingredients or atmospheric additions are required, the particles need not be coated, and the temperature is not raised over that normally used. The cost of the production operation remains essentially unchanged from that of conventional procedures. In some instances the quality of the resulting composite materials is surprisingly improved over anything previously known.
• a process for preparing a cast composite material having particles embedded in an aluminum-alloy matrix of a preselected composition that does not readily wet the particles comprises the steps of providing a molten mixture of the particles and a wetting alloy having a composition that readily wets the particles and has no alloying elements present in an amount substantially in excess of the preselected matrix composition; mixing together the molten mixture under conditions such that the wetting alloy is wetted to the particles; adding additional alloying ingredients to the melt to adjust the composition of the matrix to the preselected composition and distributing the additional alloying ingredients throughout the melt; and casting the resulting melt.
• the matrix alloy is evaluated for the presence of either wettability enhancing elements, combinations, or amounts, or wettability inhibiting elements, combinations, or amounts.
• a wetting alloy composition is designed to take advantage of that situation.
• the wetting alloy must contain not more than the required amount of each element in the final matrix alloy composition, but can contain less or none. Wetting of the matrix to the particles is then achieved with the wetting alloy. After wetting is accomplished, the composition of the matrix is adjusted with further alloying additions to reach the desired final matrix composition.
• the present invention also provides a cast composite material having a metallic alloy matrix component whose composition is carefully selected to avoid the formation of unwanted and deleterious phases during preparation, remelt, and final casting. The amount of one alloying ingredient is carefully controlled to prevent degradation of properties during remelting, formation of unwanted phases, and good castability. Other conventional alloying ingredients can be varied as necessary to attain other desirable properties of the final product. The particulate need not be altered or specially selected in order to attain good composite remelt properties.
• the novel composite material comprises a mixture of from about 5 to about 35 volume percent of nonmetallic reinforcing particles and from about 95 to about 65 volume percent of a matrix alloy, the matrix alloy being an aluminum-based alloy containing from about 8.5 to about 12.6 weight percent silicon.
• Other conventional aluminum alloying elements can be added to the matrix alloy as needed, and do not interfere with the beneficial effects of the silicon.
• Such other alloying elements include, for example, copper, nickel, magnesium, iron and manganese.
• This composite material can be prepared by a procedure which comprises the steps of preparing a molten mixture of from about 5 to about 35 volume percent of free-flowing nonmetallic reinforcing particles and from about 95 to about 65 volume percent of a matrix alloy, the matrix alloy being an aluminum-based alloy containing from about 8.5 to about 12.6 weight percent silicon; mixing the molten mixture to wet the matrix alloy to the particles and to distribute the particles throughout the volume of the melt, the mixing to occur while minimizing the introduction of gas into and retention of gas within the molten mixture; and casting the molten mixture.
• the composite material of the invention is particularly useful in remelt applications.
• the present invention provides an important advance in the art of preparation of cast composite materials.
• Composite materials can be prepared from materials combinations that are otherwise not commercially feasible, without adding special alloying ingredients or gases that might adversely affect the final product, without specially coating the particles, and without raising the temperature to unacceptably high levels.
• the present invention also provides an important advance in the art of cast composite materials, by providing a foundry remelt alloy that can be readily cast by conventional remelt practices.
• Figure 1 is a schematic illustration of a fluidity testing apparatus
• Figure 2 is a graph of fluidity test results as a function of silicon content
• Figure 3 is a micrograph of a cast composite material having an aluminum-based matrix containing 7 weight percent silicon
• Figure 4 is a micrograph of a cast composite material having an aluminum-based matrix containing 10 weight percent silicon
• Figure 5 is a micrograph of a cast composite material having aluminum-based matrix containing 10 weight percent silicon and additional alloying elements
• Figure 6 is a micrograph of another cast composite material having an aluminum-based matrix containing 10 weight percent silicon and additional alloying elements.
• a process for preparing a cast composite material having particles embedded in a matrix of a preselected composition that wets the particles only with great difficulty comprises the steps of providing a molten mixture of the particles and a wetting alloy having a composition of the preselected matrix composition but with a deficiency in a wettability inhibiting element, the wetting alloy being readily wetted to the particles during mixing; mixing together the molten mixture to wet the wetting alloy to the particles under conditions that the particles are distributed throughout the volume of the melt and the particles and the metallic melt are sheared past each other to promote wetting of the particles by the melt, the mixing to occur while minimizing the introduction of any gas into, and while minimizing the retention of any gas within, the mixture of particles and molten metal, and at a temperature whereat the particles do not substantially chemically degrade in the molten metal in the time required to complete said step of mixing; adding the wettability inhibiting elements to the melt so that the matrix has the preselected composition;
• cast composite materials can be classified into two groups, those with chemically highly reactive particles and those with chemically nonreactive particles.
• the principal obstacle with forming cast composite materials containing reactive particles is to prevent particle dissolution and unwanted formation of intermetallic compounds, while achieving wetting.
• the commercially most important reactive particle is silicon carbide.
• the principal problem with forming cast composite materials containing nonreactive particles is achieving some degree of reactivity and wetting.
• the commercially most important nonreactive particle is aluminum oxide. In each case, sufficient fluidity must be exhibited by the melt for casting.
• a process for preparing a cast composite material having particles embedded in an aluminum-alloy matrix having more than about 7 weight percent silicon comprises the steps of providing a molten mixture of the particles, and an aluminum-based wetting alloy having no more than about 7 weight percent silicon; mixing together the molten mixture under conditions such that the aluminum wetting alloy is wetted to the particles; making an addition of silicon and other elements as needed to adjust the silicon content of the melt to its desired final composition which has more than about 7 weight percent silicon, and dissolving and distributing the addition throughout the melt; and casting the resulting melt.
• a particularly useful cast composite material has reactive silicon carbide particles embedded in an aluminum-alloy matrix with about 10 weight percent silicon. Castings of this alloy can be made only with great difficulty using the approach of combining all of the ingredients together and mixing. Although the alloy can be mixed, the particulate matter enters the melt slowly, and the melt becomes so viscous that it is difficult to cast.
• a wetting alloy of aluminum plus about 7 weight percent silicon is prepared and mixed with silicon carbide particles using the approach discussed in US patents 4,759,995 and 4,786,467. Wetting of the wetting alloy to the particles is readily accomplished in about 1 hour of mixing, and the viscosity is acceptable. An addition of the remaining silicon and any other alloying additions required to adjust the matrix to the required alloy content is then made, those additions are dissolved and distributed throughout the volume of the melt, and the melt is cast.
• the cast composite material containing silicon preferably comprises a mixture of from about 5 to about 35 volume percent of silicon carbide particles and from about 95 to about 65 volume percent of a cast matrix alloy, the matrix alloy being an aluminum-based alloy containing from about 9.5 to about 11.0 weight percent silicon. Most preferably, the silicon content is about 10 percent by weight of the matrix.
• a method for preparing a cast composite material comprises the steps of preparing molten mixture of from about 5 to about 35 volume percent of free-flowing nonmetallic reinforcing particles and from about 95 to about 65 volume percent of a matrix alloy, the matrix alloy being an aluminum-based alloy containing from about 8.5 to about 12.6 weight percent silicon; mixing the molten mixture to wet the matrix alloy to the particles and to distribute the particles throughout the volume of the melt, the mixing to occur while minimizing the introduction of gas into and retention of gas within the molten mixture; casting the molten mixture; remelting the cast mixture at a temperature that reaches at least about 700"C; and recasting the remelted mixture.
• the particles are preferably silicon carbide, because of their light weight and inexpensive commercial availability in suitable forms and sizes.
• Other nonmetallic reinforcing particles such as other carbides, oxides, nitrides, solicides, and borides, may also be used.
• the particles must be "free-flowing" in the sense that they are not constrained against movement to reach a uniform distribution throughout the composite material, and are not attached or constrained by a substrate or each other, as is the case for elongated fibers.
• the particles constitute from about 5 to about 35 volume percent of the composite material. If less than about 5 volume percent is present, the composite material does not achieve properties superior to those of the conventional, non-composite material. Potentially incurring the problems of a composite material is therefore not justified by superior properties. If more than about 35 volume percent is present, the composite material is so viscous that it cannot be cast. This upper limit to the amount of particulate material can vary somewhat with the shape and type of the particulate material.
• the remainder of the composite material is the matrix alloy.
• the matrix alloy is an aluminum-based alloy containing from about 8.5 to about 12.6 weight percent silicon, balance aluminum and other alloying ingredients selected to impart particular mechanical and physical properties to the final solid composite material.
• the silicon content of the matrix is from about 9.5 to about 11.0 weight percent.
• the high silicon level has several important functions.
• the silicon influences the formation of the intermetallic compound aluminum carbide, AlC 3 , and in particular suppresses its formation.
• a carbide such as silicon carbide
• the formation of aluminum carbide is thermodynamically favoured by a negative free energy of formation.
• the aluminum carbide is hygroscopic and will absorb moisture. The result is porosity in the final cast product.
• the kinetics of aluminum carbide formation have been discovered to be such that melting and mixing of a cast composite material haivng a conventional aluminum-7 (or less) weight percent silicon alloy matrix at a controlled temperature of, for example, about 718 ⁇ C for a relatively short period of time of about one hour, permits only a small and acceptable amount of the aluminum carbide to form.
• an acceptable cast composite material can be prepared by a carefully controlled melting and mixing procedure. If, however, the cast composite material having such a conventional matrix alloy is thereafter remelted in a foundry practice of 788°C for 24 hours, the aluminum carbide formation continues at an accelerated rate.
• Aluminum carbide intermetallic compound grows from silicon carbide particles as outwardly projecting needles, which can break off to form particles in the melt.
• FIG. l illustrates a device 10 for measuring fluidity.
• Molten composite material 12 is held in a heated crucible 14, with the temperature measured by a thermocouple 16.
• One end of a hollow pyrex glass tube 18, here about 5 millimetres inside diameter, is inserted vertically into the melt 12.
• a vacuum of about 63.5 cm of mercury is applied to the other end of the tube 18 by a vacuum pump 20.
• Molten composite material is drawn up the inside of the tube 18 until the metallic portion of the composite material freezes.
• the tube 18 is removed from the melt, and the distance of travel of the composite material up the tube prior to freezing is measured.
• a number of specimens of composite material were evaluated using the apparatus of Figure 1.
• Two kilogram heats were prepared with 20 volume percent silicon carbide particles in an aluminum-alloy matrix containing varying amounts of silicon as an alloying ingredient.
• Melts were prepared with matrix silicon contents of 7, 8, 9, 10, 11, 12, and 13 weight percent silicon.
• the melts were prepared in a mixer like that disclosed in US Patents 4,759,995 and 4,786,467. The melts were cast into molds and solidified. The castings were remelted in crucibles under air at a temperature of 788°C and held for 24 hours. The temperature of the melt was reduced to 690°C +/6"C, and tested for fluidity using the apparatus of Figure 1.
• Figure 2 presents the height rise for the composite materials in inches above the melt level. The greater the height rise, the greater the fluidity.
• the fluidity increases from a low value at 7 weight percent silicon, to a level at 10 weight percent silicon that remains nearly constant with further increases in silicon content to 13 weight percent.
• Specimens were cut from the tubes and examined metallographically. The amount of aluminum carbide in the 7 weight percent silicon material was large. A much smaller amount was visible in the sample containing 8 weight percent silicon. There was no aluminum carbide visible in the alloys containing 9 weight percent or more of silicon. From these data, it was concluded that the minimum silicon content for suppression of aluminum carbide formation, in conditions of extended exposure, together with attainment of acceptable fluidity was about 8.5 percent.
• a preferred minimum silicon content was therefore selected to be about 9.5 weight percent, a level at which no aluminum carbide is present and the fluidity has nearly reached its highest level.
• the maximum silicon content of the matrix alloy according to the present invention is about 12.6 weight percent. This is the value of the aluminum-silicon eutectic composition.
• the liquidus temperature rises so that the superheat for a selected remelt temperature is reduced.
• Second, primary silicon particles are precipitated in the matrix upon solidification. The silicon particles reduce the ductility of the matrix.
• a preferred maximum silicon content is slightly lower, at 11.0 percent.
• Metallographic studies reveal that, in the range 11.0-12.6 weight percent silicon, there can be some precipitation of primary silicon in the final structure, regardless of the expected equilibrium phase diagram. Also, there is observed some shrinkage of the matrix alloy during solidification.
• the minimum silicon content of the matrix of the present composite material is therefore about 8.5 weight percent, and the preferred minimum is about 9.5 weight percent.
• the maximum silicon content of the matrix of the present composite material is about 12.6 percent, and the preferred maximum is about 11.0 percent.
• the silicon content is about 10 weight percent of the matrix, to provide a margin of error between the preferred limits of 9.5 and 11.0 weight percent, and to achieve close to the maximum fluidity possible in this general range.
• the silicon in the matrix appears to suppress the formation of aluminum carbide by altering the thermodynamic equilibria of the system.
• these equilibria are not affected by the presence of metallic alloying elements commonly provided in aluminum alloys to achieve specific properties such as strength, toughness, corrosion resistance, and the like in the final cast product.
• metallic alloying elements commonly provided in aluminum alloys to achieve specific properties such as strength, toughness, corrosion resistance, and the like in the final cast product.
• Such alloying elements include, for example, copper, nickel, magnesium, iron, and manganese.
• Example 1 To prepare a cast composite material of 20 volume percent of silicon carbide particles in a matrix alloy of 10 weight percent silicon, 1 weight percent magnesium, balance aluminum, a wetting alloy of 7 weight percent silicon, 1 weight percent magnesium, balance aluminum was prepared.
• the appropriate amounts of silicon carbide and the wetting alloy were mixed according to the procedures disclosed in US Patent 4,759,995 and 4,786,467. More specifically, the wetting alloy was melted at 671°C, and the appropriate amount of silicon carbide particles was added to the surface of the melt under vacuum over a period of 35 minutes, while the melt was mixed with an impeller. After all the silicon carbide was added, mixing was continued for another 25 minutes under vacuum. This procedure produced full wetting of the aluminum-7 weight percent silicon, 1 weight percent magnesium alloy to the particles.
• Example 2 The mixing was stopped, the chamber vented to air, and a sufficient amount of silicon was added to adjust the matrix composition to 10 weight percent silicon and 1 weight percent magnesium. The chamber was sealed and a vacuum drawn, and mixing was continued for another 15 minutes to dissolve the alloying additions and distribute them throughout the melt. The composite material was cast into pigs. The pigs were provided to a foundry for remelt, and the remelted composite material was observed to have excellent fluidity for casting into narrow mold passages.
• Example 2 Example 2
• Example 1 was repeated, except that stepped alloying was not used. That is, the conventional practice was followed wherein the final matrix alloy of 10 weight percent silicon, 1 weight percent magnesium, balance aluminum was prepared. Silicon carbide particulate in the appropriate amount was added to the melt, and the melt and particles mixed together for the same amount of time as in Example 1. The resulting melt was very viscous and could not be cast into small-diameter passages in molds.
• Example 1 is repeated, except that the composite was made to contain 10 volume 10 volume percent of silicon carbide particles.
• the final melt was fluid and could be cast into molds with both large and small passageways.
• Example 2 was repeated, except that the composite was made to contain 10 volume percent of silicon carbide particles.
• the composite materials produced with the stepped addition of alloying ingredients exhibit significantly improved post-casting properties as compared with those produced by the conventional approach.
• the second class of particles is nonreactive particles such as aluminum oxide particles.
• a process for preparing a cast composite material having particles embedded in an aluminum-alloy matrix comprises the steps of providing a molten mixture of the particles, and an aluminum-based wetting alloy having about 1 weight percent silicon and about 0.6 weight percent magnesium; mixing together the molten mixture under conditions such that aluminum wetting alloy is wetted to the particles; making an addition of elements as needed to adjust the alloy content of the melt to its desired final composition, and dissolving and distributing the addition throughout the melt; and casting the resulting melt.
• the particles are first mixed with a wetting alloy which is known to wet the particles and also has sufficient fluidity for mixing.
• a wetting alloy which is known to wet the particles and also has sufficient fluidity for mixing.
• aluminum alloys containing about 1 weight percent silicon and 0.6 weight percent magnesium readily wet aluminum oxide particles during mixing.
• Many aluminum matrix alloys of interest contain at least 1 weight percent silicon and at least 0.6 weight percent magnesium, so initial wetting can be accomplished with an aluminum alloy of that composition.
• the composition of the matrix is adjusted with further additions of alloying elements. The initial wetting is accomplished using the wetting alloy and the procedure of US Patents 4,759,995 and 4,786,467.
• a cast composite material was prepared of 10 volume percent aluminum oxide particles in an aluminum alloy containing 10 weight percent silicon, 0.6 weight percent magnesium, 0.7 weight percent iron, and 0.4 weight percent manganese.
• This cast composite material is exceedingly difficult to prepare by conventional methods, because the particles wet only slowly. The molten composite material is so viscous that it is nearly impossible to cast into a mold.
• a matrix alloy of 1 weight percent silicon, 0.6 weight percent magnesium, 0.7 weight percent iron, and 0.4 weight percent manganese, balance aluminum was melted in a crucible at 674 ⁇ C under vacuum, and the appropriate amount of aluminum oxide particles added over a period of 20 minutes.
• the aluminum-based matrix alloy contains 1 weight percent silicon and 0.6 weight percent magnesium, a composition known to achieve wetting to aluminum oxide particles. After all of the particulate matter was added, the melt was mixed under vacuum for another 20 minutes, following the approach of US Patents 4,759,995 and 4,786,467. This combination of matrix alloy composition and mixing conditions produced good wetting of the matrix alloy to the particles. Mixing was stopped, the chamber was vented to air, and sufficient silicon added to adjust the matrix content to 10 weight percent silicon (with the amounts of the other alloying additions essentially unchanged) . The vacuum was reapplied, and mixing continued for another 15 minutes. The composite was then cast into foundry pigs. The cast composite material exhibited excellent fluidity, and was suitable for preparation of castings having narrow passageways.
• a cast composite material was prepared from 20 volume percent silicon carbide particles and 80 volume percent of an alloy meeting a specification of 7 weight percent silicon, 0.3-0.45 weight percent magnesium, balance aluminum. This matrix alloy is not within the scope of the invention, and is presented for comparative purposes.
• the cast composite material was prepared by the procedures discussed previously.
• the cast composite material was remelted at a temperature of over 760 ⁇ C.
• a sample was taken of the remelted composite material, and its microstructure is illustrated in Figure 3.
• Aluminum carbide intermetallic compound is found extensively throughout the microstructure as a dark-appearing phase. In Figure 3, circles have been drawn around some of the aluminum carbide particles and regions for illustrative purposes.
• Example 7 was repeated, except using a matrix alloy that meets a specification of 10 weight percent silicon, 0.8-1.0 weight percent magnesium, balance aluminum. Except for the higher silicon content within the preferred range of the invention and a minor difference in magnesium content, this matrix alloy has the same composition as that of Example 7.
• the microstructure of this alloy is shown in Figure 4. There is no aluminum carbide visible in the microstructure.
• Example 7 was repeated, except using a matrix alloy that meets a specification of 10 weight percent silicon, 0.6-1.0 weight percent iron, 3.0-3.5 weight percent copper, 0.2-0.6 weight percent manganese, 0.3-0.6 weight percent magnesium, 1.0-1.5 weight percent nickel, balance aluminum.
• This matrix alloy is within the scope of the invention, having 10 weight percent silicon. " It is a more complex alloy in that it also contains iron, copper, manganese, and nickel.
• This cast composite material is suitable as a die casting alloy.
• Figure 5 illustrates the microstructure of this cast and then remelted alloy. There is no aluminum carbide visible in the microstructure.
• Example 7 was repeated, except using a matrix alloy that meets a specification of 10 weight percent silicon, 2.8-3.2 weight percent copper, 0.8-1.2 weight percent magnesium, 1.0-1.5 weight percent nickel, balance aluminum.
• This matrix alloy contains copper and nickel in addition to the silicon within the range of the invention and magnesium.
• This composite material is suitable as a high temperature sans and permanent mold casting alloy.
• Figure 6 illustrates the microstructure of this cast and remelted alloy. There is no aluminum carbide visible in the microstructure.
• Example 8 demonstrates that the addition of silicon to within the range of the invention suppresses aluminum carbide formation, as compared with the alloy of Example 7.
• Examples 9 and 10 demonstrate that additions of other alloying elements do not interfere with the suppression of aluminum carbide formation by the high silicon content.
• the results of Figure 2 demonstrate that the 10 weight percent silicon alloy has excellent fluidity and it was observed to have good castability.
• the composite material of the invention provides an important commercial advance in the art of cast composite materials.
• the material can be mixed and cast by a primary composite material supplier, and shipped as a cast ingot to a foundry for remelting and casting into precise shapes as required.
• the composition of the matrix alloy is selected so that the remelting practice at the foundry may be similar to conventional remelt practices, which would not be possible for a cast composite material of conventional alloying content.
• Excellent fluidity is retained by the molten composite material even when it is held in a remelt crucible for extended periods of time and at temperatures previously thought to be unacceptably high because they produce undesirable reaction products.

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• 1991
  • 1991-07-12 EP EP95108612A patent/EP0671478A3/en not_active Ceased
  • 1991-07-12 CA CA002086520A patent/CA2086520C/en not_active Expired - Lifetime
  • 1991-07-12 WO PCT/CA1991/000242 patent/WO1992001821A1/en active IP Right Grant
  • 1991-07-12 DE DE69120415T patent/DE69120415T2/de not_active Expired - Fee Related
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• 1993
  • 1993-01-15 NO NO930141A patent/NO300899B1/no not_active IP Right Cessation
• 1994
  • 1994-11-25 AU AU79031/94A patent/AU669309B2/en not_active Ceased
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