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High reinforcement content metal matrix composites are produced by the infiltration of molten Al alloys into preforms of ceramic particles using the PRIMEX™ pressureless metal infiltration process. These composites possess low density, very high specific stiffness, high fatigue strength, and good corrosion resistance, making them excellent candidates for automotive brake caliper applications. Most current production brake calipers are fabricated from ductile iron. Ductile iron provides good stiffness and fatigue strength, requirements for the application, but also possesses high density and poor corrosion resistance. The introduction of preform infiltrated metal matrix composites into brake caliper applications, however, has been slow due to the complex geometry. Low cost, high volume preform fabrication techniques suited to the production of full fist caliper preforms that can be subsequently infiltrated with molten Al alloy do not currently exist.

High reinforcement content aluminum metal matrix composites were produced by pressureless liquid metal infiltration into high green density preforms of SiC and Al2O3. Characterization of the composites was performed, providing physical and mechanical properties. The composites were shown to provide significant weight savings over ferrous materials, while possessing the requisite properties for stiffness critical (e.g., brake calipers), fatigue critical (e.g., connecting rods), and wear critical (e.g., brake caliper pistons) applications. In addition, the damping behavior of the materials was studied. The results suggest that high reinforcement content metal composites possess the ability to absorb energy and reduce noise, thus providing utility in components that require noise reduction (e.g., brake pad backing plates).

Metal matrix composites were produced by the PRIMEX™ pressureless metal infiltration process. Properties of the composites were determined as a function of particulate loading, filler type, alloy chemistry, and test temperature. Using the property data, a generic brake caliper bridge geometry was designed and modeled. The results of the modeling suggested that composite caliper bridges can be equivalent in stiffness to ductile iron components at only 43% of the mass, and equivalent in stiffness to aluminum components at only 60% of the mass. In addition, composites containing unreinforced regions (i.e., areas without ceramic particulates) were fabricated to facilitate drilling and tapping at attachment locations. The strength of the threads in these regions was evaluated and compared with thread strengths in iron, Al alloy, and monolithic metal matrix composite.