Influence of thermomechanical treatments on microstructural stability of titanium modified austenitic stainless steel

The influence of thermomechanical treatments on the microstructural stability of a 15Cr-2.2Mo-15Ni Ti modified austenitic stainless steel was studied. The thermomechanical treatments involved imparting cold work followed by aging in the temperature range 873-1123 K. The cold work was varied from 15 to 22.5% at intervals of 2.5%. The influence of cold work level on recrystallisation kinetics was studied by determining the activation energy for recrystallisation. In the temperature range 873-1023 K the stability of the cold worked microstructure was enhanced by the retardation of recovery and recrystallisation by TiC precipitation. The retardation was more effective for 20% cold work than for other cold work levels. At temperatures of 1073 and 1123 K the degree of retardation was more effective for 20% cold work than for other cold work levels. At temperature of 1073 and 1123 K the degree of retardation of recovery and recrystallisation by precipitates was reduced owing to coarsening of the precipitates. Higher activation energy for recrystallisation and hence slower recrystallisation kinetics were observed for 20% cold work compared with other cold work levels. The optimum cold work level resistant to recovery and recrystallisation was identified as 20%. (C) The Institute of Materials.