So the second bit of feedback I got from my knife fighter friend was that her training blades always get banged up in knife to knife fighting. I made the blades form 6061 aluminum, and was curious how it would hold up.
I mounted some scrap stock in a vise and did some slash cuts on it, then let my friend do the same. I marked the blades with sharpie so that the damage would show up better.
*Ahem* I looked like I was waving a tiny baseball bat around with one hand and her strokes looked like she was performing an appendectomy. The result of both our cuts though was gouges on the blade. So while 6061 Aluminum is probably fine for training knife defenses, I think I will want to make the final training blades from tool steel so that they can also be used in knife to knife training.