TEM investigation of reduced activation ferritic/martensitic alloys developed by thermodynamic modeling

Two reduced activation ferritic/martensitic (RAFM) alloys with chemical compositions guided by thermodynamic modelling were designed, fabricated, and me-chanically tested in previous work. The experimental alloys demonstrated significantly refined grain and subgrain size with a high density of dislocations leading to higher yield and tensile strength with respect to EUROFER97-2 without sacrificing the impact toughness. This improvement has been achieved thanks to the dedicated chemical and thermal treatment that alternates the nucleation, growth and coarsening as well as enables the presence of high-density small precipitates as compared to EUROFER97 steel. In this work, TEM investigation was performed to quantitatively describe the microstructural parameters such as the average sizes of M23C6 and MX particles, number density of the particles and dislocation density. Furthermore, the strengthening contribution of each microstructural feature was calculated, and the correspondence of the total strength derived via microstructure to the measured yield strength is discussed.

Automated summary

Two RAFM alloys with improved microstructures and mechanical properties were designed and tested, showing higher yield and tensile strength without sacrificing impact toughness. This improvement was achieved through dedicated chemical and thermal treatments, resulting in refined grain and subgrain size and a high density of dislocations. TEM investigation was conducted to quantitatively describe the microstructural parameters and calculate the strengthening contribution of each microstructural feature.