Metal matrix composites, and methods for making the same

Abstract

A holder comprising an insert for reinforcing a metal matrix composite article and methods of making the same. In another aspect, the present invention provides metal matrix composite articles reinforced with an insert(s) and methods of making the same. Useful metal matrix composite articles comprising the inserts include brake calipers.

Description

[0001] This application claims priority to U.S. provisional application having Serial No. 60 / 404,729, filed Aug. 20, 2002, the disclosure of which is incorporated herein by reference.[0002] The present invention relates to metal matrix composite insert holder and metal matrix composite articles made using metal matrix composite insert holders.DESCRIPTION OF RELATED ART[0003] Reinforcement of metal matrices with ceramics is known in the art (see, e.g., U.S. Pat. Nos. 4,705,093 (Ogino), 4,852,630 (Hamajima et al.), 4,932,099 (Corwin et al.), 5,199,481 (Corwin et al.), 5,234,080 (Pantale), and 5,394,930 (Kennerknecht), Great Britain Pat. Doc. Nos. 2,182,970 A and B, published May 28, 1987 and Sep. 14, 1988, respectively, and PCT applications having publication nos. WO 02 / 26658, WO 02 / 27048, and WO 02 / 27049, published Apr. 4, 2002). Examples of ceramic materials used for reinforcement include particles, discontinuous fibers (including whiskers) and continuous fibers, as well as ceramic ...

AI Technical Summary

Benefits of technology

[0040] cooling the molten metal to provide a metal matrix composite article. Surprisingly, embodiments of the present invention can be used to make metal matrix composite articles wherein the molten metal in the mold to be in the molten state for less than 75 seconds (in some embodiments, preferably less than 60 seconds). By contrast, conventional methods tend to require the molten metal in the mold is in the molten state for 200 seconds or more. Although not wanting to be bound by theory, it is believed that the presence of the metal having a positive Gibbs oxidation free energy above at least 200.degree. C. enables formation of a bond between the holder and / or insert, as applicable, and the metal of the metal matrix composite article (in some embodiments, preferably without an oxide layer at the interface) and hence does not require an extended period of heating of the interface by molten aluminum or aluminum alloy, as applicable to attempt to break up the oxide layer to achieve metallurgical bonding.

Problems solved by technology

Hence, for a given size and shape, a brake caliper made from cast aluminum has significantly lower mechanical properties such as bending stiffness and yield strength than the cast iron caliper.

Typically, the mechanical properties of such an aluminum brake caliper are unacceptably low as compared to a cast iron brake caliper.

Many conventional MMCs typically contain enough ceramic reinforcement material to make machining or welding impractical or even impossible.

Another consideration in designing and making MMCs is the cost of the ceramic reinforcement material.

In addition, the cost of ceramic oxide materials such as the polycrystalline alpha-alumina fibers, is substantially more than metals such as aluminum.

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