Effect of Phase-Selective Nanoscale Precipitates on the Bauschinger Effect in Austenitic–Ferritic Duplex Stainless Steels

Abstract

AbstractThe Bauschinger effect in austenitic–ferritic duplex stainless steel 1.4462 was investigated using tension–compression tests combined with electron backscatter diffraction (EBSD). A major focus was on the impact of phase-selective nanoscale α′ precipitates formed in the ferritic phase due to 475 °C embrittlement. Contrary to the general knowledge that coherent precipitates have only a short-range effect and thus no significant influence, a strong increase in the Bauschinger effect was detected. Based on EBSD data and cyclic micro-indentations in individual grains, it was demonstrated that α′ precipitates enhance the phase difference between austenite and ferrite and increase deformation incompatibility and local dislocation density gradients at phase boundaries. Thus, despite their small size and coherence, α′ precipitates lead to long-range back stresses that significantly enhance the Bauschinger effect. In addition, the influence of precipitation was shown to depend on the extent of pre-strain during initial loading. The insights demonstrate that the influence of precipitates on the Bauschinger effect is highly complex and always needs to be analyzed with respect to precipitation characteristics, microstructure, and external boundary conditions.