Casting Porosity

Casting porosity is a property of cast metal that causes the metal to appear sponge-like under high magnification. Porosity  is inherent in the casting process. It can be caused by internal shrinkage, gas evolution, oxide films,  inclusions, etc. The presence of casting porosity does not render the casting defective. A certain level of casting porosity is acceptable in most products.

Casting porosity in aluminum electric motor
 cooling fan.

Cases involving Casting Porosity:
Motor Cooling Fan Failure
Clevis Pin Failure