Metal Matrix Composites

The property benefits of MMCs allow engineers to replace heavy cast iron parts with fibre reinforced light alloys without sacrificing performance. The methods used to achieve the gains cost-effectively involve a combination of pressure casting and fibre preform shapes to selectively reinforce the engine components. Application successes include reinforced pistons, engine blocks and cylinder heads Saffil alumina fibres are used to reinforce aluminum alloys and result in greatly enhanced modulus and high temperature tensile and fatigue strength, lower thermal conductivity and thermal expansion, and superior wear resistance.

Preforms for Cast Metal Composites

Preforms based on performance-proven Saffil Alumina Fibre are used as reinforcement materials for cast aluminium and magnesium automotive components.
The preform is a rigid and porous shape containing discontinuous Saffil Alumina Fibre, and possibly one or more additional reinforcement materials. These additional materials include particles of aluminium oxide, silicon carbide, and titanium dioxide, or other fibre reinforcements such as graphite. A large selection of standard preform compositions are available from Saffil’s perform partners, as well as customized compositions and shapes.
Preforms can be used in precision casting processes such as squeeze casting and high-pressure die casting. The preform is preheated and then placed in the casting die. When the molten metal is forced into the die cavity under pressure, it infiltrates the porous preform and thereby incorporates the reinforcement material as an integral part of the cast component’s microstructure. This type of material is known as a Metal Matrix Composite (MMC) or Fibre Reinforced Metal (FRM).
The result is a high performance cast component with material properties which are tailored to a specific application. Using preform technology, many material characteristics features properties can be modified, including mechanical, vibration and thermal properties. Because the density of Saffil Alumina Fibre is only slightly higher than that of aluminium (3.3 g/cc vs. 2.7 g/cc), these material properties can be modified with adding little or no additional mass, and in many cases the superior mechanical properties of the composite material enable vital weight reductions to be achieved.

Engineered Microstructures Deliver Performance

Preform technology disconnects the intrinsic link between component geometry and engineering mechanics. This is accomplished by providing a product that enables the local modification of the components microstructure, and thereby freeing the automotive engineer from a predefined set of monolithic material properties. This new found freedom can result in a large variety of performance enhancements:
Locally increase strength and stiffness
Tune the component's natural frequencies
Decrease the natural frequency density
Increase the alloy's vibration damping capacity
Improve mechanical properties at elevated temperatures
Prevent creep and fatigue failure in thermally stressed components
Control thermal expansion

These examples are just some of the creative and cost-effective ways in which automotive engineers have used Saffil fibre-based preforms to improve the performance of cast aluminium and magnesium parts.
Ultimately, increased performance must translate to an improvement in the bottom-line via increased competitiveness (cost or market share) and fibre preforms help MMCs accomplish this in terms of :
Improved power and handling for performance vehicles
Reduction in vehicle noise, vibration, and harshness (NVH)
Cross-platform commonization of components
Lighter and more fuel efficient engines and vehicles
Reduced warranty costs due to quieter and more durable parts

Over the last two decades, Saffil fibre preform technology has made a significant impact on the mechanical systems of many production vehicles, and the list of applications continues to expand:
Engine blocks (cylinder liners and bearing caps)
Cylinder heads (valve seats and guides)
Pistons (ring grooves and combustion bowls)
Brakes (calipers and rotors)
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