grain refinement and improved tensile properties of ti-modified aisi 316l stainless steel by cold rolling and annealing

Aisi 316 stainless steel is one of the most widely used in the industry. nevertheless, the risk of sensitization and intergranular corrosion due to the formation of chromium carbide is a major drawback when the steel is exposed to a temperature range of 500-800 °c. alloying with strong carbide-forming elements such as ti reduces the content of free carbon in the matrix to solve this problem, introducing stabilized stainless steel. regarding the mechanical properties of austenitic stainless steels, it is well-known that the average grain size is a key parameter for fine-tuning the mechanical properties. grain refinement by cold rolling and subsequent eversion/recrystallization treatments is routinely used to improve the mechanical properties of austenitic stainless steels. while this strategy has been investigated for aisi 316 and 316l austenitic stainless steels, limited work on the room temperature mechanical properties as well as on the grain refinement and recrystallization behavior during thermomechanical processing of 316ti stainless steel is available. accordingly, in the present work, the effects of ti microalloying and thermomechanical processing on the recrystallization behavior during elevated temperature annealing and the resulting mechanical properties were investigated. the results showed that, besides the temperature of rolling and reduction in thickness, the strain-induced α'-martensitic transformation is sensitive to the presence of ti and c in solid solution or their presence as tic carbides in the aged condition. during annealing at 800 °c, the reversion of martensite to austenite and primary recrystallization of the retained austenite resulted in the formation of a fine-grained microstructure with average grain size of ~2.5 μm. moreover, at this temperature, the precipitation of tic and sigma phase was found to be important in the retardation of recrystallization and grain growth as well as refining the grain size. however, annealing the cold rolled 316ti stainless steel at 900 °c resulted in a coarser average grain size of 4 μm but without the presence of the unfavorable sigma phase. the yield stress (ys) of 480 mpa, ultimate tensile strength (uts) of 805 mpa, and total elongation of 68% were obtained for annealing at 900 °c, revealing the merits of ti addition and thermomechanical processing for the improvement of mechanical properties. the yield stress data for samples with equiaxed recrystallized microstructures followed a specific hall-petch line, which reveals that the ti microalloying and thermomechanical processing can be used to adjust the average grain size (d) for tailoring the mechanical properties. the hall-petch equation of ys=193+567.5/√d was obtained, in which ys and d have been expressed as mpa and μm, respectively.