Internal stresses in a 15%Cr ferritic stainless steel after large strain unidirectional processing

An interstitial free ferritic stainless steel was cold worked to a total strain of 4.6. The largely strained steel is characterized by a submicrocrystalline structure consisting of elongated grains/subgrains with the transverse size of about 210 nm; and the fraction of high-angle grain boundaries is about 0.6. Following a rapid rise at an early processing stage, the dislocation density in (sub)grain interiors unusually decreased after total strains of above 2. Nevertheless, the samples are characterized by high residual stresses that result in complex elastic distortions of the crystal lattice within the elongated crystallites. Such internal stresses are shown to be originated from deformation grain boundaries including low-angle subboundaries.