jimmyh

Unfortunately I don't know the ultimate source of that data or anything about the experiments that went into it, but it it isn't something he just made up. He traced over this one in pretty colors, which I believe originally came from some metallurgy book Alvin Johnston (of rec.knives) had.

In the 1095 temper chart I was able to find here, the unnotched charpy shows no evidence of embrittlement, but it shows up quite dramatically in torsion, rapidly dropping off at a fairly low temperature. What causes this difference?

I had the same idea recently, and I think it should be possible. The rate of diffusion is much lower for most alloying elements than it is for carbon, but it isn't zero (at 1200C, Cr is 1690x slower and Mo is 16,800x slower, according to Verhoeven). If you start with powder, mix it well, and then fold it a few times, the diffusion distance starts to become small enough to be practical. 325 mesh powder, forged to 50% and folded twice, should result in a diffusion length equal to the layer thickness after only an hour at 1040C. The spacing between different components would be more t