Originally Posted by FBinNY

If you note, i prefaced the post saying that the details matter. I was simply offering a possibility to consider.

Until the OP provides details, including an explanation of his stress relief process, we can only throw stuff against the wall to see what sticks.

However, having seen similar failures over the years, I admittedly tend to blame mechanics more than I do metal. However, I don't have enough info to offer an opinion, just a possibility to consider.

Lastly, there's no point debating. It's up to the OP to consider the possibilities posted here, factor those with his own experience and draw his own conclusions.