Cold deformation and heat treatment influence on the microstructures and corrosion behavior of AISI 304 stainless steel

In the present study AISI 304 stainless steel with different degrees of cold deformation and annealing parameters were investigated. Microstructural evolutions by optical micrography and scanning electron microscopy showed relatively fully austenitic ultrafine-grained structure obtained after annealing at 700°C for 80 min. The volume fraction of α'-martensite increased with increasing compressive deformation rate and maximum volume fraction of α'-martensite was attained in the samples subjected 0·65% strain. The potentiodynamic polarization results in 3% NaCl indicated that the corrosion current density increased with cold deformation, while after annealing, it reduced from 2·86 to 2·29 μA cm-2, showing an enhancement of corrosion resistance. The immersion test showed that the austenitic ultrafine-grained structure exhibits moderate and more uniform pitting corrosion attack compared to the coarser grain in NaCl solution