The Effects of Martensite Thermomechanical Parameters on the Formation of Nano/Ultrafine Grained Structure in 201LN Stainless Steel

In this study, the effects cold rolling and annealing parameters during thermomechanical processing of the AISI 201LN stainless steel were investigated. The cast samples were homogenized, hot-rolled and solution-annealed to acquire a suitable microstructure for the subsequent thermomechanical treatment. Unidirectional and transverse multi-pass cold rolling at 25, 0 and -15 °C was carried out to 90% reduction in thickness, followed by annealing at temperature range of 700–900 °C for different times of 15–1800 s. Microstructures were characterized by optical and scanning electron microscopy, X-ray diffraction and feritscope measurements. Hardness test was also used for evaluating mechanical properties of the specimens. The results showed that the saturation strain of martensite formation during the cold rolling at 25, 0 and -15 °C in 201LN stainless steel was about 0.29, 0.23 And 0.17, respectively. A nano/ultrafine grained structure was formed by annealing the 90% cold rolled specimen at 800 °C for 60 s with a grain size of about 300 nm.