Aluminum fatigue memory

[elesdee]

Can somebody explain or provide some resources about fatigue memory of aluminum? I'm finding it hard to find info that I can understand as someone with high school physics knowledge.

From what I gathered, aluminum ages and becomes weaker and more brittle as it endures stress and impacts. Eventually it fails by cracking. This is in the context of 6005 and 7005 alloys.

Also, this is different from steel in that steel can take relatively infinite amount of stress as long as it's under a certain threshold. In other words, steel doesn't age like aluminum.

I am right?

[realazy]

It has to do with the crystal structure. FCC, BCC, etc.

BCC (body centered cubic) has infinite fatigue life if you stay under half of the ultimate yield strength.

Aluminum and aluminum alloys are not BCC and therefore have a finite fatigue life.

That's all I could remember without digging through my old notes and textbooks.

[elesdee]

Thanks for the reply Lazy.

Does heat treating restore the fatigue memory? Also, does heat treating warp the object?

Anyone else got any info?