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Description
The main aim of this paper is to evaluate the mechanical properties and microstructure of 316LN high-nitrogen austenitic stainless steel after rolling under ambient and cryogenic conditions. Cryorolling was realized after cooling in liquid nitrogen bath at 77 K. During the rolling at ambient temperature (TA) can take place the dynamic recovery of the microstructure. This is strongly retarded by rolling under cryogenic conditions (TC). The main plastic deformation mechanism at ambient temperatures is slip. When the temperature is decreased to cryogenic level and the strain is increased, scanning electron microscope analysis showed the slip is accompanied by deformation bands and twins. In this case, stored energy also increases. For thermal analysis differential scanning calorimetry was carried out.
Samples were tested by tensile test according to the standards at three different temperatures: TT = <4.2; 293> [K]. Total deformation after rolling was in the range ε = <10; 50> [%]. The values of the mechanical properties are YS = <524; 1870> [MPa], UTS = <715; 2118> [MPa], depending on the rolling and testing temperatures. Generally, the total elongation decreased with increasing total deformation and decreasing testing temperature. The values of elongation for TA after deformation ε = <10; 50> [%] and TT = <4,2; 77; 293> [K] are in the range A5 = <1.5; 46> [%]. For TC and the same deformations and temperatures ranges, A5 = <3.7; 43> [%].