HK1261213B - Device and method for forming a metal matrix composite vehicle component - Google Patents

Description

Apparatus and method for forming metal matrix composite components

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 62/291,200, filed on February 4, 2016, entitled DEVICE AND METHOD FOR FORMING AND SQUEEZE-CASTING A COMPOSITE BRAKE DRUM, and U.S. Provisional Application No. 62/398,042, filed on September 22, 2016, entitled DEVICE AND METHOD FOR FORMING AND SQUEEZE-CASTING (ISOSTATIC INFILTRATION) A COMPOSITE BRAKE DRUM, ROTOR, OR VEHICLE COMPONENT, the disclosures of which are incorporated herein by reference in their entireties.

Technical Field

The present application relates generally to metal matrix composite components, and more particularly to metal matrix composite vehicle components, such as brake drums and brake rotors, and apparatus and methods for making the same.

Background Art

Metal matrix composites (MMCs) are generally made by incorporating reinforcements into a metal matrix. For example, an MMC may comprise a ceramic preform infiltrated with a metal. MMCs generally have properties and physical characteristics different from metals, which may be desirable depending on the application. For example, relative to the metal surrounding the MMC, the MMC may have higher specific strength, higher Young's modulus, higher temperature resistance, higher lateral stiffness and strength, higher resistance to moisture absorption, higher electrical and thermal conductivity, lower density, and higher wear resistance. The specific physical properties of the MMC generally depend on the final application and can be modified by changes in both the matrix and the metal alloy used.

Vehicles may include drum brakes and/or disc brakes. Drum brakes generally consist of a rotating drum-shaped portion called a brake drum. The drum brake's shoes, or pads, press against the inner surface of the drum, causing friction and reducing the drum's rotation. Disc brakes generally consist of a rotating brake disc or rotor. The brake caliper has brake pads that press against the exterior and interior of the disc, causing friction and reducing the disc's rotation. During vehicle braking, there is typically a high energy transfer to the friction surfaces of the brake drum or disc, which can cause temperatures to rise.

Summary of the Invention

Disclosed herein are exemplary embodiments of metal matrix composite components and apparatus and methods for manufacturing the same.

An exemplary method for manufacturing a metal matrix composite vehicle component includes: using a mold including a male mold portion and a female mold portion having mold surfaces and a plurality of spacers; heating the mold to a casting temperature; placing a ceramic preform on the plurality of spacers, the ceramic preform being spaced apart from at least one of the mold surfaces by the spacers; closing the mold to form a mold cavity between the mold surfaces of the male mold portion and the female mold portion, the ceramic preform being disposed within the mold cavity; providing molten metal into the mold cavity; and pressurizing the molten metal to a casting pressure for a casting duration to infiltrate the ceramic preform, thereby forming the metal matrix composite vehicle component.

An exemplary mold for manufacturing a metal matrix composite vehicle component includes: a male mold portion and a female mold portion having mold surfaces; a mold cavity formed by the mold surfaces when the mold is in a closed state; a plurality of spacers extending from at least one mold surface; and a plurality of spacers extending from at least one mold surface. The spacers are configured to support a preform spaced apart from the at least one mold surface, and the mold is configured to receive molten metal to cast the metal matrix composite vehicle component.

For example, the metal matrix composite vehicle component of the present application is produced by using any of the methods or molds disclosed herein. For example, the metal matrix composite vehicle component may include: a metal matrix composite portion; a metal portion that is substantially free of metal matrix composite material; and a recess extending from an outer surface of the metal portion to the metal matrix composite portion.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will be better understood with reference to the following description and accompanying drawings, in which:

FIG1 is a perspective view of an exemplary casting apparatus for a metal matrix composite brake drum, wherein the casting apparatus is in an open state;

FIG2 is a cross-sectional view of the casting apparatus of FIG1 along line A-A, wherein the casting apparatus is in an open state and a preform is positioned in a mother mold;

FIG3 is a cross-sectional view of the casting apparatus of FIG1 along line A-A, wherein the casting apparatus is in a closed state and the preform is positioned in the mother mold

FIG4 is a cross-sectional view of the casting apparatus of FIG1 taken along line A-A, wherein the casting apparatus is in a closed state and molten metal fills the mold cavity;

FIG5 is a cross-sectional view of an exemplary brake drum removed from the casting apparatus of FIG4 , shown as taken along line A-A in FIG4 ;

FIG6 is a perspective view of an exemplary casting apparatus for a metal matrix composite brake rotor, wherein the casting apparatus is in an open state;

FIG7 is a cross-sectional view of the casting apparatus of FIG6 along line B-B, wherein the casting apparatus is in an open state and the preform is positioned in the mother mold;

FIG8 is a cross-sectional view of the casting apparatus of FIG6 taken along line B-B, wherein the casting apparatus is in a closed state with the preform positioned within the female mold;

FIG9 is a cross-sectional view of the casting apparatus of FIG6 taken along line B-B, wherein the casting apparatus is in a closed state and molten metal fills the mold cavity;

FIG10 is a cross-sectional view of an exemplary brake rotor removed from the casting apparatus of FIG9 , shown as taken along line B-B; and

11 is a flow chart describing an exemplary method of manufacturing a metal matrix composite vehicle component.

DETAILED DESCRIPTION

As described herein, when one or more components are described as being connected, coupled, attached, coupled, attached, or otherwise interconnected, such interconnection may be direct between the components, or may be indirect, such as through the use of one or more intermediate components. Also as described herein, references to "component," "component," or "portion" should not be limited to a single structural component, member, or element, but may include an assembly of components, components, or elements. Also as described herein, the terms "substantially" and "approximately" are defined as at least approaching (and including) a given value or state (preferably within 10% thereof, more preferably within 1% thereof, and most preferably within 0.1% thereof). Also as described herein, the term "casting apparatus" is defined as any apparatus suitable for forming a metal component, such as, for example, a mold or die for forming molten metal into a metal component.

Metal matrix composites embedded with light weight metals (e.g., aluminum alloys) are useful in many industries, such as aerospace, automobiles, heavy trucks, railways, national defense, etc. Components made of light weight metal alloys comprising local MMC portions can be used in any part of a vehicle to reduce the weight of the component while maintaining or improving other features of the material, such as, for example, wear resistance, durability, strength, thermal conductivity, etc. Many different vehicle components comprising local MMC portions (i.e., MMC portions are limited to certain areas of the component) can be formed using the methods described in this application. Although the rotation and rotationally symmetrical components formed with local MMC portions (specifically, brake drums and rotors) are discussed in detail below, other non-rotational and non-rotationally symmetrical vehicle components, such as, parts of a vehicle body, a vehicle frame, or a vehicle suspension, can also be manufactured using the methods described below.

MMCs are generally manufactured by incorporating reinforcements into a metal matrix, thereby strengthening the composite's structure. MMCs generally consist of two parts: a primary inorganic metal portion and a porous structure made from other inorganic components, such as fused silicon carbide. The non-metallic portion of the MMC can be incorporated into the metal portion through additive and preforming techniques.

Forming MMCs through additive processes such as stir casting involves incorporating non-metallic materials directly into molten metal. Specifically, stir casting involves adding non-metallic reinforcements directly to the molten metal while stirring it, where the surface energy of the additive is higher than the surface tension of the molten metal. These additive methods are used to produce automotive brake components, such as Alcan and Lanxide components.

However, these additive manufacturing techniques have the problem of making large-scale production of MMC components too expensive. Brake rotors produced using Duralcan technology (a stir casting technology for combining silicon carbide with aluminum) illustrate these problems. For example, using this technology, among other inconsistencies, the silicon carbide is unevenly distributed within the aluminum alloy, resulting in some silicon carbide particles protruding from the rotor surface. In addition, the silicon carbide particles are spread throughout the brake rotor. Therefore, special tools are required to machine the cast part because the silicon carbide is scattered throughout the aluminum. Various deficiencies of the Duralcan process are described in U.S. Patent No. 6,547,850. A stir casting apparatus designed by Alcan Aluminum Company is described in U.S. Patent No. 5,531,425.

Forming an MMC by a preforming process involves forming a non-metallic preform of a reinforcement material infiltrated with a metal alloy such as aluminum. Applicants have developed various MMCs and methods for manufacturing MMCs, including aluminum MMCs. Examples of such MMCs and related methods are described in U.S. Patent No. 9,429,202 (herein, "the '202 patent") and U.S. Published Patent Application No. 2016/0108980 (i.e., U.S. application serial number 14/536,311; herein, "the '311 application"), both of which are incorporated herein by reference in their entirety. If the material incorporated by reference contradicts or is inconsistent with this specification, this specification will replace any such material. Any reference cited herein does not admit that these references are prior art to the present invention.

Applicants have shown (for example, in the '202 patent and the '311 application) that certain vehicle brake components can be formed with localized MMC portions, rather than mixing MMC material throughout the entire vehicle component. These MMC components are produced by placing MMC preforms in desired locations before casting the part. The molten metal used to cast the part infiltrates the ceramic preform to form the localized MMC portion of the final cast part. For example, an MMC portion can be formed on the wear surface of a brake rotor, as shown in FIG. 6A of the '311 application.

When forming a component such as a vehicle component including an MMC portion, a ceramic preform is generally first manufactured. The ceramic compound used to form the ceramic preform may include a variety of components, such as ceramic particles, reinforcing fibers, starch, an organic porous material, a low-temperature binder, a high-temperature binder (e.g., colloidal silica), and/or water. These materials can be combined by wet and dry methods. The ceramic preform may have a porosity ranging from about 50% to about 80%, or a porosity of about 60%.

Ceramic compounds and preforms can be made by a variety of methods that produce preforms that can be cast by the methods described herein. For example, a method for preparing ceramic compounds is disclosed below. First, the reinforcing fibers undergo a detangling process. Dry materials (e.g., ceramic particles, reinforcing fibers, starch, and organic porous generating materials) are then gradually added to a one-pot system and weighted. Wet materials (e.g., low-temperature adhesive and high-temperature adhesive and water) can then be slowly added to the same one-pot mixture, stirred, and then mixed under reduced pressure. The uniform one-pot mixture is substantially free of voids and has randomly oriented fibers and a scalable concentration. The mixture is then loaded into a press and compressed by a male and female mold. This compression molding technique provides a uniform structure to the preform. Once the preform is molded, it is removed from the press and dried in a humid environment, supported by an absorbent liner. Once the water is removed from the preform, the preform and the absorbent liner are heated to extreme temperatures to remove the organic material and fuse the inorganic ceramic particles. Upon cooling, the ceramic preform is machined to the appropriate size, the outer layer of the skin is removed, and the pores of the preform are exposed. As described above, the preform can be prepared using a dry pressing technique, in which water is not included in the mixture.

Next, the preform is substantially infiltrated with metal, determined based on the desired properties of the MMC component. This is accomplished by placing the heated preform in a mold and forcing the aluminum into the mold cavity with sufficient pressure to saturate the preform and achieve the desired casting pressure. The cast portion can then undergo heat treatment and processing to achieve the desired features and dimensions of the vehicle component. For example, the component can undergo a T7 heat treatment process.

During the casting process, the molten metal can be pressurized indirectly or directly. Direct pressurization refers to pressurizing the molten metal by closing the mold. Indirect pressurization refers to pressurizing the molten metal with a piston or other mechanism that pressurizes the metal within the closed mold.

In some production methods of MMC vehicle components, for example, by horizontal die casting, a preform is loaded into the male portion of the mold or onto the upper box so that the preform is aligned within the component. Loading the preform into the upper box can sometimes result in a damaged preform due to misalignment with the upper box or due to thermal shock. In order to insert the preform into the upper box of the mold without damaging the preform, tight manufacturing tolerances are generally required, for example, a gap as small as 0.003'' around the preform. After inserting the upper box of the mold, the mold is closed and the molten metal is injected into the mold (indirectly pressurized in the middle of the injection sleeve or cavity) under high pressure, for example, as, about 7000 to about 12000 pounds per square inch. The high-pressure molten metal can also impact the preform unevenly, which can also damage the preform or push it out of alignment.

Similar problems can arise with direct squeeze casting. In direct squeeze casting, the preform is loaded into the female portion of the die, and molten metal is added before the die closes. The male portion of the die is then closed to pressurize the molten metal and squeeze it into the preform. During the extrusion process, the molten metal flows around the preform and can damage it or push it out of alignment.

In order to help preform alignment during casting, the upper box of the mold for these casting technologies is usually tapered between about 0.75 ° to about 1.5 °. Tapering also promotes the removal of cast parts from the mold. After casting, the MMC material is processed to remove the draft angle to produce the desired shape. Due to the highly wear-resistant silicon carbide in the MMC, processing aluminum MMC is significantly more difficult than processing pure aluminum. As mentioned above, due to the use of sharp and expensive diamond-based tools, this also leads to increased costs. During processing, the aluminum alloy containing silicon carbide from the MMC removed from the drum is generally waste and cannot be recycled.

According to an embodiment of the present application, an MMC vehicle component is formed by an isostatic infiltration process. The exemplary casting method and apparatus of the present application reduce the stress experienced by the preform during setup and casting, and reduce the amount of waste generated during the casting process. As described herein, the term "isostatic infiltration" describes the infiltration of a preform with molten metal so that the pressure exerted by the metal on the mold and the preform is uniform or uniformly distributed throughout the molten metal. Therefore, the preform is not disturbed by the molten metal and maintains its position during casting. Isostatic infiltration can be performed by an indirect squeeze casting technique, which involves placing the preform in the female portion of the mold, closing the mold, filling the mold with molten metal, and then pressurizing the molten metal to cause it to infiltrate the preform.

The apparatus and method of the present application allow for maintaining the position of a ceramic preform during casting, thereby improving the positioning accuracy of the MMC within the cast component and reducing waste and non-recyclable scrap. Because the preform can be selectively positioned within the MMC vehicle component, the component includes an MMC portion and a metal portion that is substantially free of MMC material. While maintaining the preform in a spaced relationship with the mold surface, the selective positioning of the preform within the MMC vehicle component also allows for the use of smaller preforms without the preform cracking during loading into the mold. The use of smaller preforms reduces the overall cost of the MMC vehicle component, as the material used to form the preform is generally more expensive than the metal alloy.

The exemplary squeeze casting apparatus of the present application includes a male mold portion, referred to as an "upper box," and a female mold portion, referred to as a "lower box," each having a mold surface. When the mold is in a closed state, a mold cavity is formed between the mold surfaces of the male and female molds. At least one mold also includes a pin or spacer that supports the preform in a spaced relationship with at least one of the mold surfaces of the male and female mold portions during the casting process. That is, these spacers or pins allow the preform to be positioned within the mold so that some or all surfaces of the preform do not contact the mold surface. As described above, these spacers allow the preform to be precisely positioned within the mold cavity without the need to position the preform on the upper box of the male mold, thereby reducing the likelihood of damage to the preform during loading into the mold. The spacers also reduce contact between the mold and the preform, so that less heat is lost from the preform when the mold is closed and before the molten metal is introduced into the mold cavity. When filling the die cavity, the spacer provides space between the preform and the die surface so that the molten metal can flow freely and provides equal pressure to all sides of the preform so that the preform is not damaged or displaced by the flowing molten metal. These spacers can be machined into the mother mold or can be separated from the mold. The spacer can be tapered, with a larger base at the mold and a smaller part at the preform, and have any shape, for example, as a cone, cylinder, ridge, dome, pyramid, etc. In some embodiments, the spacer is formed by material that is infiltrated or consumed during casting (for example, the material of the preform) and thus becomes part of the cast part. The spacer can also be an extension of the preform, for example, a "pillar" that supports the preform above the surface of the mother mold and positions the preform in the die cavity.

As another benefit, the exemplary casting techniques described herein can be used to cast vehicle components from metal alloys that are typically considered difficult to cast and infiltrate into MMC components, such as metal alloys with low magnesium content. For example, alloys 319, 355, 356, and 357 aluminum can be used in the exemplary casting processes disclosed herein.

As a further benefit, the exemplary casting techniques of this application allow cast parts to be heat treated using a T7 heat treatment process. The T7 heat treatment process involves heating the part to a solution phase, quenching, and then aging the cast part. Parts cast using high-pressure die casting techniques are difficult to treat using the T7 process because the porous internal structure of the die-cast part leads to gas inclusions in the solution phase that cause bubbles. Parts manufactured using the casting techniques disclosed herein do not suffer from this problem.

Referring now to FIG. 1 , an exemplary mold 100 for isostatically pressing a metal matrix composite brake drum according to an embodiment of the present application is shown. Mold 100 includes a male mold portion 110 having a mold surface 112, and a female mold portion 120 having a mold surface 122. Female mold portion 120 includes a spacer 130 extending above mold surface 122. Male mold portion 110 includes a pressurized chamber 102 for pressurizing the molten metal during casting. In some embodiments, the positions of the male and female mold portions may be reversed.

Spacers 130 may be included in both the male mold 110 and the female mold 120 and may be located anywhere within the mold cavity 140 (see FIGS. 2-3 ) and may support the ceramic preform 150 (see FIGS. 2-3 ) from below, above, from the side, or any combination thereof. The spacers 130 maintain the preform 150 in a spaced relationship from at least one of the mold surfaces 112 , 122 . Although four spacers 130 are shown in the illustrated embodiment, any number of spacers 130 may be included in the mold 100 . The spacers 130 may be formed from the same material as the preform 150 or from another high-temperature resistant material, such as a ceramic or metal alloy (e.g., tool steel or cast iron). As described above, the spacers 130 are tapered, i.e., they have a draft to allow for removal after infiltration and casting of the component. The reduced contact area at the top of the spacers 130 reduces heat transfer from the spacers 130 and into the mold 100 . As described above, spacers can be included on any surface of the mold to contact any portion of the preform. For example, spacers can be included on the top and bottom of the preform to space it from the top and bottom mold surfaces. The preform can also be held in place on the spacers by gravity.

Spacers 130 may be permanently formed in one or both of molds 110, 120. Spacers 130, integrally formed with molds 110, 120, have a draft or taper toward preform 150 to provide release when the cast part is removed from mold 100. Integrally formed spacers 130 are generally formed from the same material as mold 100, such as, for example, tool steel. Removable spacers may be used in conjunction with integrally formed spacers as needed. Removable spacers allow the same mold to be used to produce parts with or without localized MMC sections. Spacers may also include a tapered portion to aid in aligning the preform during loading into the casting apparatus. Spacers may extend from the mold surface any distance necessary to position the preform in the desired position, depending on the shape of the mold cavity and the specific application. In certain embodiments, the spacers extend from the mold surface by approximately 0.05 inches to approximately 0.2 inches, or at least approximately 0.1 inches, or at least approximately 0.05 inches.

Referring now to FIG2 , a cross-section of the mold of FIG1 is shown along line A-A. Mold 100 is shown in an open position with male mold portion 110 and female mold portion 120 spaced apart. Ceramic preform 150 is positioned on spacers 130 in female mold portion 120 and spaced apart from mold surface 122. Draft angles may be provided in one or both of male mold portion 110 and female mold portion 120 to allow for removal of the component after casting.

3 , the mold 100 is shown in a closed state. The mold surfaces 112, 122 of the male mold portion 110 and the female mold portion 120 form a mold cavity 140 that surrounds the preform 150. The male mold 110 and the female mold 120 are moved into contact with each other and locked together so that they do not separate during pressurization of the mold cavity 140.

4 , mold 100 is shown in a closed state and filled with molten metal 160 . Pressurizing piston 106 is depressed through pressurizing chamber 102 in the direction of arrow 104 to pressurize molten metal 160 causing it to fill mold cavity 140 and penetrate preform 150 .

Referring now to FIG. 5 , an exemplary brake drum 162 is shown removed from mold 100 and in its final machined state. Brake drum 162 includes an MMC portion 164 and a metal portion 166 substantially free of MMC material. As described above, a recess 168 extending from the outer surface of metal portion 166 to MMC portion 164 is formed in metal portion 166 by spacers 130. MMC portion 164 can have a thickness ranging from approximately 0.05 inches to the full thickness of the component. In certain embodiments, the MMC portion has a thickness ranging from approximately 0.2 inches to approximately 0.5 inches, or from approximately 0.25 inches to approximately 0.45 inches.

The excess aluminum removed after casting the brake drum 162 can roughly cover the inner and outer diameters of the preform 150. Since the mold surfaces 112, 122 are not used to position the preform 150 in the mold cavity 140, the gap between the preform 150 and the mold surfaces 112, 122 is filled with metal, which is substantially free of MMC material. To remove this excess material, a two-part machining process can be used. The first machining step involves using conventional machining tools to remove the metal portion, without the need for special tools for machining MMC material. The second machining step involves using special tools to form the finished surface of the MMC portion. The material removed during the first machining step is substantially free of MMC material and can be recycled, which reduces the waste generated during the production of MMC vehicle components.

Referring now to FIG. 6 , an exemplary mold 200 for isostatically pressing a metal matrix composite brake disc is shown. Mold 200 includes a male mold portion 210 having a mold surface 212, and a female mold portion 220 having a mold surface 222. Female mold portion 220 includes a spacer 230 extending above mold surface 222. Male mold portion 210 includes a pressurized chamber 202 for pressurizing the molten metal during casting. In some embodiments, the positions of the male and female mold portions may be reversed.

Spacers 230 may be included in both the male mold 210 and the female mold 220 and may be located anywhere within the mold cavity 240 (see FIGS. 2-3 ) and may support the ceramic preform 250 (see FIGS. 2-3 ) from below, above, from the side, or any combination thereof. The spacers 230 maintain the preform 250 in a spaced relationship with at least one of the mold surfaces 212 , 222 . Although four spacers 230 are shown in the illustrated embodiment, any number of spacers 230 may be included in the mold 200 . The spacers 230 may be formed from the same material as the preform 250 or from another high-temperature resistant material, such as a ceramic or metal alloy (e.g., tool steel or cast iron). As described above, the spacers 230 are tapered, i.e., they have a draft to allow for removal after infiltration and casting of the component. The reduced contact area at the top of the spacers 230 reduces heat transfer from the spacers 230 and into the mold 200 .

Spacers 230 may be permanently formed in one or both of molds 210, 220. Spacers 230, integrally formed with molds 210, 220, have a draft or taper toward preform 250 to provide release when the cast part is removed from mold 200. Integrally formed spacers 230 are formed from the same material as mold 200, such as, for example, tool steel. Removable spacers may be used in conjunction with integrally formed spacers as needed. Removable spacers allow the same mold to be used to produce parts with or without localized MMC sections. Spacers may also include a tapered portion to aid in aligning the preform during loading into the casting apparatus. Spacers may extend from the mold surface any distance necessary to position the preform in the desired position, depending on the shape of the mold cavity and the specific application. In certain embodiments, the spacers extend from the mold surface by approximately 0.05 inches to approximately 0.2 inches, or at least approximately 0.1 inches, or at least approximately 0.05 inches.

Referring now to FIG7 , a cross-section of the mold of FIG6 is shown along line B-B. Mold 200 is shown in an open position with male mold portion 210 and female mold portion 220 spaced apart. Ceramic preform 250 is positioned on spacers 230 in female mold portion 220 and spaced apart from mold surface 222. Draft angles may be provided in one or both of male mold portion 210 and female mold portion 220 to allow for removal of the component after casting.

8 , mold 200 is shown in a closed state. Mold surfaces 212, 222 of male mold portion 210 and female mold portion 220 form a mold cavity 240 surrounding preform 250. Male mold 210 and female mold 220 are moved into contact with each other and locked together so that they do not separate during pressurization of mold cavity 240.

9 , mold 200 is shown in a closed state and filled with molten metal 260 . Pressurizing piston 206 is pressed downwardly through pressurizing chamber 202 in the direction of arrow 204 to pressurize molten metal 260 causing it to fill mold cavity 240 and penetrate preform 250 .

Referring now to FIG. 10 , an exemplary brake disc 262 is shown removed from mold 200 and in its final machined state. Brake disc 262 includes an MMC portion 264 and a metal portion 266 substantially free of MMC material. A recess (not shown) extending from the outer surface of metal portion 266 to MMC portion 264 is formed in metal portion 266 by spacers 230. In the illustrated embodiment, the recess is not noticeable in the final machined state of brake disc 262 because metal portion 266 is machined away from both sides of MMC portion 264 after casting. In certain embodiments, the recess is present in the final machined brake disc 262. MMC portion 264 can have a thickness ranging from approximately 0.05 inches to the full thickness of the component. In certain embodiments, the MMC portion has a thickness ranging from approximately 0.2 inches to approximately 0.5 inches, or from approximately 0.25 inches to approximately 0.45 inches.

The excess aluminum removed after casting the brake disc 262 can substantially cover the top and bottom surfaces of the preform 250. Since the mold surfaces 212, 222 are not used to position the preform 250 in the mold cavity 240, the gap between the preform 250 and the mold surfaces 212, 222 is filled with metal that is substantially free of MMC material. To remove this excess material, a two-part machining process can be used. The first machining step involves removing the metal portion using conventional machining tools, without the need for special tools for machining MMC material. The second machining step involves forming the finished surface of the MMC portion using special tools. The material removed during the first machining step is substantially free of MMC material and can be recycled, which reduces the waste generated during the production of MMC vehicle components.

Although the various embodiments described and illustrated herein illustrate a single preform for forming an MMC vehicle component, multiple preforms may be supported by spacers in a mold for forming an MMC vehicle component having one or more MMC portions. Furthermore, although the molds illustrated in Figures 1-10 are arranged in a vertical orientation, the casting techniques of the present application may also be applied to horizontal casting apparatuses or any casting apparatus oriented at any angle.

Referring now to FIG11 , a flow chart illustrating an exemplary method 1100 for forming a metal matrix composite vehicle component is shown. Exemplary method 1100 includes providing a mold at 1102, comprising a male mold portion and a female mold portion each having a mold surface, and a plurality of spacers extending from or above at least one of the mold surfaces of the male and female mold portions; heating the mold to a casting temperature at 1104; placing a ceramic preform on the plurality of spacers such that the preform is spaced apart from the mold surface at 1106; closing the mold to form a mold cavity between the mold surfaces of the male and female mold portions at 1108, with the ceramic preform disposed within the mold cavity; providing molten metal into the mold cavity at 1110; and pressurizing the molten metal to a casting pressure for a casting duration to infiltrate the ceramic preform at 1112, thereby forming the metal matrix composite vehicle component. Exemplary method 1100 may be implemented using any of the casting apparatuses described above.

In certain embodiments, the casting temperature may range from about 500°F to about 1200°F, or may be about 1000°F or higher. Prior to placement in the mold, the preform may be heated from about 1000°F to about 1500°F, or greater. During infiltration, the molten aluminum may range from about 1000°F to about 1200°F, depending on the alloy used. The casting pressure may range from about 10,000 pounds per square inch to about 16,000 pounds per square inch, or may be about 15,000 pounds per square inch or greater. In certain embodiments, the clamping force required to hold the mold sections of the mold together is about 1000 tons. The casting duration is generally no greater than about three minutes, or in the range of about 20 seconds to about 40 seconds, or about 27 seconds. Applicants note that in certain embodiments, low temperatures and pressures may be used to cast metal matrix vehicle components, eg, casting temperatures ranging from about 400°F to about 600°F, and casting pressures ranging from about 8,000 psi to about 12,000 psi.

Although the various inventive aspects, concepts and features of the present disclosure may be described herein and shown as being implemented in combination in an exemplary embodiment, these various aspects, concepts and features may be used in many alternative embodiments independently or in various combinations and sub-combinations thereof. Unless expressly excluded herein, all of these combinations and sub-combinations are intended to be within the scope of the present application. Furthermore, although various alternative embodiments (such as alternative materials, structures, constructions, methods, devices and components, alternatives regarding form, coordination and function, etc.) regarding the various aspects, concepts and features disclosed may be described herein, such description is not intended to be a complete or exhaustive list of available alternative embodiments, whether currently known or developed later. Those skilled in the art may easily adopt one or more of the inventive aspects, concepts or features to other embodiments and uses within the scope of the present application, even if these embodiments are not expressly disclosed herein.

In addition, even though some features, concepts or aspects of the present disclosure may be described herein as preferred arrangements or methods, such description is not intended to imply that such features are required or essential unless expressly stated otherwise. Further, exemplary or representative values and ranges may be included to aid in understanding the present application, however, these values and ranges should not be construed in a limiting sense and are intended to be critical values or ranges only where expressly stated.

Furthermore, while various aspects, features, and concepts may be expressly identified herein as inventive or forming part of the disclosure, such identification is not intended to be exclusive, and rather there may be inventive aspects, concepts, and features fully described herein that are not expressly identified as such or as part of a specific disclosure, the disclosure being instead set forth in the appended claims. Descriptions of exemplary methods or processes are not limited to inclusion of all steps as required in all cases, nor are the steps presented in an order that is to be construed as required or necessary unless expressly so indicated. The terms used in the claims have their full ordinary meaning and are not limited in any way by the description of the embodiments in the specification.

Claims (20)

1. A method for manufacturing a metal matrix composite vehicle component, the method comprising: The mold used includes: The male mold portion having the mold surface; The mother mold portion having the mold surface; and Multiple spacers; Heat the mold to the casting temperature; A ceramic preform is placed on the plurality of spacers, wherein the ceramic preform is spaced apart from at least one of the mold surfaces by the spacers, and each spacer has a taper toward the ceramic preform to help align the ceramic preform during loading into the mold. The mold is closed to form a cavity between the mold surfaces of the male mold portion and the female mold portion, and the ceramic preform is arranged within the mold cavity; Molten metal is supplied to the mold cavity; and During the casting duration, the molten metal is pressurized to the casting pressure to permeate the ceramic preform, thereby forming the metal matrix composite vehicle component. 2. The method according to claim 1, wherein pressurizing the molten metal includes isostatic pressurizing the mold cavity, wherein the molten metal applies equal pressure to the side of the ceramic preform exposed to the molten metal. 3. The method according to claim 1, characterized in that: The ceramic preform comprises ceramic particles, reinforcing fibers, and a high-temperature binder; and The ceramic preform has a porosity ranging from 50% to 80%. 4. The method according to claim 3, wherein the ceramic preform has a porosity of 60%. 5. The method according to claim 1, wherein the molten metal comprises aluminum. 6. The method according to claim 1, characterized in that: The casting temperature range is from 500℉ to 1200℉; The casting pressure ranges from 10,000 pounds per square inch to 16,000 pounds per square inch; and The casting duration shall not exceed three minutes. 7. The method according to claim 1, wherein the casting pressure ranges from 8,000 pounds per square inch to 12,000 pounds per square inch. 8. The method according to claim 1, wherein the casting temperature range is from 400℉ to 600℉. 9. The method according to claim 1, wherein the casting duration is 27 seconds. 10. The method according to claim 1, wherein the method further comprises: The metal matrix composite vehicle component is heat-treated using the T7 heat treatment process. 11. The method according to claim 1, wherein the mold comprises four spacers. 12. The method according to claim 11, wherein the four spacers are arranged in two pairs, wherein the spacers in each pair are arranged on opposite sides of the mold cavity. 13. The method according to claim 1, wherein the ceramic preform is centered in the mold cavity and is supported equally by each of the spacers. 14. The method according to claim 1, characterized in that: The master mold portion is a bottom mold portion having a bottom mold surface; and The spacer extends above the bottom mold portion and is configured to space the ceramic preform from the surface of the bottom mold. 15. The method according to claim 1, wherein the metal matrix composite vehicle component comprises: Metal matrix composite portion; and There is no metallic component in the composite material with a metal matrix. 16. The method according to claim 15, wherein at least a portion of the metal matrix composite portion is disposed on the outer surface of the metal matrix composite vehicle component. 17. A metal matrix composite vehicle component manufactured according to the method of claim 1. 18. A mold for manufacturing metal matrix composite vehicle components, comprising: The male mold portion having the mold surface; The mother mold portion having the mold surface; and The mold cavity formed by the mold surfaces of the male mold portion and the female mold portion when the mold is in the closed state; and A plurality of spacers extending from at least one of the mold surfaces of the male mold portion and the female mold portion; The spacers are configured to support preforms spaced apart from at least one of the mold surfaces, and each spacer has a taper toward the preform to aid in alignment of the preform during loading into the mold; and The mold is configured to receive molten metal to cast the metal matrix composite vehicle component. 19. The mold for manufacturing metal matrix composite vehicle components according to claim 18, characterized in that it further comprises: At least one heating element for heating the mold to a casting temperature ranging from 400℉ to 1200℉. 20. The mold for manufacturing metal matrix composite vehicle components according to claim 18, characterized in that it further comprises: A pressure piston for pressurizing the molten metal in the mold cavity to casting pressures ranging from 8,000 psi to 16,000 psi.