Mechanical Behavior of VNS9-Sh TRIP Steel after Tempering

The influence of tempering at temperatures of 300–650°C on the mechanical properties of austenitic–martensitic VNS9-Sh TRIP steel under static tension and fatigue conditions, on its phase composition, and on the residual macrostresses in it is studied. A significant change in the mechanical properties is detected after tempering at 500°C or above. When the tempering temperature increases, the amount of strain-induced martensite decreases, and an the reverse martensite transformation occurs intensely at 600°C. Tempering at above 600°C leads to an increase in the amount of the α phase, which mainly consists of alloyed ferrite. The level of compressive residual stresses decreases from 950 MPa in the initial state to 750 MPa after tempering at 600°C.