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Selectively Reinforced Casting

Diagram of Centrifugal Casting Process and Setup

Technology Category: Casting and Solidification

Description: Selectively Reinforced Casting (SRC), is a process developed at Pacific Northwest National Laboratory (PNNL) to produce inhomogenously reinforced or functionally graded material (FGM) components from stir-cast particulate metal matrix composites (MMC). The process uses the radial forces generated from centrifugal casting to segregate a second discrete phase from the matrix of MMC materials. The relative difference in density between the matrix alloy and reinforcement phase defines the direction of segregation (to the inside or outside of the casting), as well as the ease of segregation. Virtually all MMC systems can be used in SRC, the most common being the aluminum-ceramic MMC materials.

The primary advantage of SRC, is the ability to selectively place the reinforcement in an area of the casting that is the most beneficial, hence leaving non-critical areas free from reinforcement. This is advantageous for complex areas that require extensive machining, or where it is not desirable to have reinforcement. Furthermore, the reinforcement is placed in specific areas of a component to locally enhance properties and exploit the characteristics of composites.

SRC MMC Powertrain Components

Selectively Reinforced Casting can produce parts with a high density of particles in the reinforced region. Reinforcement density can reach levels >=50% by volume, with starting feedstock levels of only 10%. This can reduce the material cost of a MMC component, by minimizing the amount of costly reinforcement phase needed in the feedstock material.

Parts can be cast to near-net shape and finished to final dimensions with a secondary process such as coining or machining operations. Typical dimensional casting tolerances are in the range of 0.1%, with surface finishes dependant upon the casting mold finish. Component characteristics and reinforcement placement/levels can be tailored easily by altering casting parameters.

Application: The Pacific Northwest National Laboratories has produced a number of prototype powertrain components for the automotive sector utilizing selectively reinforced casting technology. Due to their improved characteristics over conventional alloys, metal matrix composites can be used in higher temperature applications where an increase in strength, modulus of elasticity and wear are desirable.

Point of Contact: Darrell Herling (509) 376-3892 or Mark Smith (509) 376-2847