system
Given the following post, respond as if you're commenting on Reddit:
human
Why are depleted uranium penetrators "self sharpening"?

I keep hearing that depleted uranium is "self sharpening" and the best explanation I've found is that DU burns away on the edges. While I don't doubt this is true, it still doesn't explain what exactly it is about DU that causes it to happen instead of having the nose rounded over. 

(and yes I already know about post-pen effects so you don't need to explain that)
gpt
I work on similar self sharpening materials, and it's typically due to the way the material deforms. If it has very little plasticity,it can form shear bands. These can form into a crack, and happen at very specific angles. If your material is brittle enough, and fails the right way, the edges of the fracture surface can get very sharp. Think of how glass or obsidian fracture.