Effect of porosity and tension-compression asymmetry on the Bauschinger effect in porous sintered steels

The Bauschinger effect is a common phenomenon in metallic materials. In this paper, the Bauschinger effect in Fe-0.85Mo-2Ni powder metallurgy (PM) steel was investigated for different porosities and as a function of loading sequence (compression-tension versus tension-compression). Both the porosity and loading sequence had a significant effect on the magnitude and asymmetry of Bauschinger effect. Compression followed by tensile loading lead to a higher Bauschinger effect than tension followed by compression. This asymmetry of Bauschinger effect was more significant for higher porosity. Crack formation and propagation, observed in this study, were the main factors influencing the asymmetry in Bauschinger effect. Finite element analysis, based on the actual microstructure of the steels, yielded good agreement with the experimental stress-strain behavior. FEM showed that both the Bauschinger effect in the steel matrix and porosity contribute to the global Bauschinger effect of the PM steels.