TRIP steels for automotive deep drawing

Recent (early 2010s) automotive steel development achieving 50%+ necking strain via martensitic transformation, as an alternative to superplasticity.

Or you can plot the log of stress versus strain and get the slope, which is equal to n, and you can prove that your necking strain for a circular tensile bar is just equal to your strain hardening exponent. Anybody have an idea what the strain hardening exponent for low-carbon steel or aluminum might be? It's on the order of 0.2. Could be 0.15 for higher-strength steel, could be 0.25 for lower-strength steel. For martensitic stainless steel, it can be 0.5 rather than 0.2, because this is a transformation-induced plasticity — remember I passed around the ferrite pot and the magnetism — it changes crystal structure, so you get increased plasticity. Your necking strain goes to a much higher value. Instead of 20% strain it's going to go to 50% strain before you get necking, or even more.