Mechanical properties evolution on heat treated severe cold rolled UNS S32760 Super Duplex Stainless Steel

Super Duplex Stainless Steels (SDSSs) are characterized by the compresence of austenitic and ferritic grains. They display very high corrosion resistance, especially in chloride-rich environments. They also have better mechanical properties than single-phase counterparts. In the recent years, many studies have been performed to enhance the mechanical properties of SDSS without detrimental effects on corrosion resistance. In this work, Super Duplex Stainless Steel AISI F55 - UNS S32760 is cold rolled and heat treated at different temperatures and holding times to obtain a serious enhancement of the mechanical properties of the material. Much attention is devoted to the optimization of the heat treatment performed on the plastically deformed material, in order to obtain a suitable compromise between tensile strength and ductility, without the formation of undesired embrittling phases. The heat treatment at 620° C was considered the best compromise, combining 1539 MPa of tensile strength with 8,25 % of fracture elongation after 12,5 minutes of holding time. A detailed microstructural analysis has been carried out to understand the strengthening mechanisms acting on the material and to explain the evolution of the microstructure that leads to superior mechanical properties of the treated steel. The corrosion resistance of the heat treated material has been checked for the most promising thermo-mechanical treatments.