Effects of solution heat treatment on grain growth and degree of sensitization of AISI 321 austenitic stainless steel

This work investigates the influence of solution temperature on grain growth and degree of sensitization of AISI 321 steel. Samples were solution treated at temperatures between 800 and 1,200°C for 80 min and sensitized at 600°C for 105 h. Optical microscopy and double loop electrochemical potentiodynamic reactivation (DLEPR) techniques were used to characterize and evaluate the degree of sensitization. The grain coarsening temperature (Tgc) found was 1,080°C, with occurrence of abnormal or discontinuous grain growth. Samples submitted to solution heat treatment below 1,080°C presented average grain diameter approximately equal to those presented by non-heat treated samples. The sensitization process at 600°C for 105 h became null when the samples were previously solution treated at 800 or 900°C, for 80 min. Sensitized and previously solution treated samples for temperatures greater than 1,075°C presented a decrease in sensitization intensity and an increase in transgranular precipitation.