Something I have been wondering about is the ETA carbides that form in cryo, but not sub-zero. IIRC, they are only there after cryo, and once tempered they dissolve. Is this true? At a structural level, what improvement would cryo result in over sib-zero, as long as Mf is reached by -110f? It seems obvious that Mf at -200f would benefit from cryo, but that's not what we are talking about here.