Effects of Solution Treatment on the Microstructure and Mechanical Properties of UNS S32750/F53/1.4410 SDSS (Super Duplex Stainless Steel) Alloy

The influence of solution treatment time on the microstructural and mechanical properties of a super duplex stainless steel was investigated. A solution annealing treatment at 1120 °C was applied to the hot-rolled alloy, with soaking times varying between 10 and 30 min. The microstructural characteristics before and after solution treatment were examined using XRD and EBSD techniques by measuring lattice parameters and micro-strains, weight fraction, average grain size, and maximum misorientation angle. The experimental results showed that the constituent phases are δ-Fe and γ-Fe, regardless of the alloy state. The mechanical properties of the solution-treated alloy were evaluated by tensile testing, measuring the ultimate tensile strength (σ_UTS), yield strength (σ_0.2), fracture strain (ε_f), and impact toughness (KCV). Increasing the solution treatment time from 10 min to 30 min leads to improved ductility and reduced mechanical strength, with the volume of the ferrite phase increasing, the average austenite grain size decreasing, and the maximum misorientation angle decreasing. This is due to the ability of ferrite to absorb stress and to the greater participation of grains in the deformation process. Important decreases in high elastic strains and residual stress fields after solution treatment were also noted.