Effect of TMCP on Microstructure and Mechanical Properties of 304 Stainless Steel

The present study investigates the evolution of microstructure and mechanical properties of 304 stainless steel after thermo-mechanical controlled processing (TMCP). Three different FRTs (finish rolling temperatures) have been adopted and the micro-constituents are identified as austenite grains, stacking faults, annealing, and deformation twins. Fine austenite grains in the range of 1-30m are obtained at lower FRT (700 degrees C) whereas at higher FRT, coarse grains are formed. TEM and X-ray analyses indicate the formation of M23C6 ((Cr, Fe)(23)C-6) precipitates for higher FRT (900 degrees C). Specimen processed with 700 degrees C FRT results into 37% enhancement in UTS compared to the base metal which is attributed to fine partially recrystallized grain, extensive deformation twinning and high dislocation density. Maximum elongation (68%) is obtained due to the formation of strain-free equiaxed grains (approximate to 40m) at 900 degrees C FRT.