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

The 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 alpha ' precipitates formed in the ferritic phase due to 475 degrees 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 alpha ' 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, alpha ' 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.

Automated summary

The Bauschinger effect in austenitic-ferritic duplex stainless steel 1.4462 was investigated, and it was found that alpha ' precipitates formed in the ferritic phase significantly enhance the Bauschinger effect, contrary to the general belief. The presence of these precipitates increases the phase difference between austenite and ferrite, leading to enhanced deformation incompatibility and local dislocation density gradients. Despite their small size and coherence, the alpha ' precipitates generate long-range back stresses that contribute to the Bauschinger effect.