Other Ceramic-reinforced Metal Parts.
Whisker reinforcement can be costly, so researchers have focused considerable attention on adding inexpensive particles of aluminum oxide or silicon carbide, rather than whiskers, to aluminum.
Although the properties of parts reinforced this way haven't been as high-grade as when whiskers have been used, the parts nevertheless seem adequate for many automotive components.
For example, aluminum reinforced with ceramic particles was made into car engine connecting rods and proved to have higher strength and more resistance to the stresses imposed by the engine than the metal alloy currently used.
Another aluminum alloy with alumina particles as reinforcement looks promising for long drive shafts.
Long drive shafts in trucks and some planned cars have a rotational stability problem at high speed--that is, they start to vibrate like a rubber band that's been plucked. Adding 20 percent alumina particles makes the drive shaft about 3 percent stiffer, enough of an increase in stiffness to keep the drive shaft from vibrating at high speed.
Ceramic-reinforced metals have great potential, but cost is a problem.
In most cases, automotive companies won't use a new material until they can get the cost down to what they are paying for the current material.
Some innovative fabrication processes have been developed to decrease the cost of ceramic-reinforced metals.
One process involves heating a block of the composite to a temperature at which the block can be forged (deformed under pressure and heat into a special tool that has the shape of the desired part).
Another process loosely bonds together ceramic particles into porous preform of the a desired shape and then lets molten metal soak into the preform and fill the pores.
In this process, the ratio of ceramic to metal can be varied anywhere from 40 parts ceramic 60 parts metal to about 80 parts ceramic/20 parts metal, so that a whole family of materials with different properties is possible.
A third process, which only works for up to about 30 to 40 percent ceramic particles, involves heating the metal-ceramic mixture to above the melting temperature of the metal and pouring the thick-as-molasses mixture into a shaped ceramic mold to cool and become solid.