Enhanced solute diffusion to promote shear-type reverse transformation recovery in metastable austenitic stainless steel

The martensite reverse transformation behavior and the effect of microstructure differences on mechanical properties were investigated in metastable austenitic stainless steel. During continuous heating, whether annealing or pulsed electric field treatment, the deformation-induced martensite transforms to austenite by diffusionless shear reversion. In subsequent isothermal holding, the samples treated by pulsed electric treated accomplish the reverse transformation from martensite to austenite, and forming the equiaxed, defect-free austenite grains, but the martensitic reversion in annealed samples is incomplete, consisting of the diffusiontype austenite, lath-type austenite and dislocation cells. The difference in microstructure is caused by atomic diffusion in essence. Under a pulsed electric field, the atom receives an electric force that reduces the activation energy required for diffusion. Therefore, the atom diffusion is promoted, which accelerates the dislocations climbing and subgrain boundaries coalescence and then promoting the schedule of recrystallization. As a result, the difference in microstructure has a significant effect on the mechanical properties, i.e., the annealed coldrolled austenitic stainless steels have higher strength with poor ductility, yet the pulsed steels present an excellent ductility. The reason for the difference in mechanical properties is likely to the phase transformationinduced plasticity responses.

Automated summary

The study revealed that in metastable austenitic stainless steel, the martensite reverse transformation behavior and microstructure differences have a significant impact on mechanical properties. Pulsed electric field treatment can promote the reverse transformation of martensite to austenite, leading to equiaxed, defect-free austenite grains with excellent ductility.