I've been having pretty decent results by peening with some very soft aluminium rods I bought on ebay. I think they are used for soldering normally.

You can see it's softer than brass when you cut the rod (goes through like butter) and when you peen it, goes very fast.

The razor is as thight as with brass rods and I open/closed is maybe 25 times and it did not degrade the peening yet.

But do you guys think that the fact that this material is very soft makes it a bad material for peening? I mean, over the long term.

thanks