Fabrication of Reinforced Aluminum Brake Calipers Via Pressureless Metal Infiltration of Multi-Piece Preforms

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. To this end, a multi-piece preform approach was developed. Multiple ceramic particle preforms of relatively simple geometry were produced and assembled into a full caliper shape. The assembly was then infiltrated with molten Al alloy to yield a single-piece full fist caliper. The present work describes the fabrication concept, provides a generic full fist caliper design suited to the multi-piece approach, and shows example components. Also, static and fatigue properties obtained with test specimens containing a preform joint are presented.