Aluminum porosity–strength proportionality

In steel you can get hydrogen embrittlement. There is no embrittlement with hydrogen in aluminum; there's only porosity. People have done extensive studies looking at the percentage of porosity on the fracture surface versus the tensile strength. So full strength is 50 ksi, and if I have up to 40% porosity I lose 40% of my strength. Aluminum is a fairly ductile metal, no hydrogen embrittlement, and my strength reduction is directly proportional to the volume fraction of porosity. I can have 5% porosity, I lose 5% of my strength. It's not usually a big deal. You do lose more of your elongation — it's a little steeper loss in elongation — so it doesn't stretch as far.

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