Alumium Based Alloy Main Bearings

These materials were developed as an improvement on the white metal
and copper based alloys and to provide bearings that carry high loads.

Special features include good resistance to corrosion, high thermal conductivity,and
high fatigue strength. The disadvantages are only
moderate embedding properties, poor compatibility ,and high coefficients
of thermal expansion. If used as solid unbacked bearings this type of
alloy is usually too weak to maintain an interference fit and too hard
to run satisfactorily against an unhardened shaft.

As a bearing material unalloyed aluminum has a tendency to seize
to a steel mating surface. It was found that 20% of tin added to
the aluminum improved seizure resistance and that cold working and
annealing helped to prevent brittleness. The difference in
coefficients between aluminum and steel necessitates work hardening
the bearing before use to prevent loosening in service.