Polished Section of a Porous Weld in Aluminum Casting Alloy #356

This is an unetched section showing the porosity in a weld on an aluminum casting. There are many potential sources for the porosity including wet welding gas, organic contaminants on the surface of the casting, and high porosity in the original casting. In this case, cleaning the surface of the casting removed the porosity.

Reflected Brightfield Illumination

Definition/Function:

Aluminum Alloy #356 is a very common casting alloy. It contains 7% silicon and 0.35% magnesium with less than 0.25% copper, less than 0.35% manganese, less than 0.6% iron, and less than 0.35% zinc.

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References:

Shackelford, James F. and William Alexander, MATERIALS SCIENCE AND ENGINEERING HANDBOOK, 3rd EDITION, CRC Press, p. 136, 2001