Comment by kragen

It's a good question; unusually, that doesn't mean I don't have a good answer.

Steel is so far from being a more or less uniform substance that it's not even funny. There are four major phases that play roles even in the commonest carbon steel (ferrite, cementite, austenite, and martensite), plus others that can form at times like graphite, which plays an important role in cast irons. Ferrite and cementite can form nanolaminated microstructures called pearlite and bainite which have a major influence on the properties of the steel, and there are other microstructures that form depending on cooling speed, heat treatment, and cold working. So even the simplest steel is a nanostructured composite of metal and ceramic whose properties are hard to model computationally, though great strides have been made in recent decades.

Then, once you add other alloying elements besides those two (intentionally or not), steel stops being so simple. You can find phase diagrams for most of the binary systems (vanadium-carbon, for example, or vanadium-iron) but most of the ternary systems probably include compounds that haven't been identified yet. In theory you could find them computationally, I think. Even when you have a phase diagram, though, that doesn't tell you how fast the phase transitions happen, which depends on things like the crystal structures of intermediate unstable phases.

I don't know anything about this stuff, I just read about it. Recommended! Start with https://www.tf.uni-kiel.de/matwis/amat/generalinfo_en/guided...