Bauschinger effect in porous sintered steels

The Bauschinger effect was investigated in a sintered Fe–Mo steel by conducting load reversal experiments in tension followed by compression and vice-versa. A significant difference in Bauschinger effect was observed based on the initial direction of loading, with a much stronger Bauschinger effect in the compression–tension than in the tension–compression loading sequence. Stress–strain hysteresis measurements and examination of microstructure evolution indicated that compressive followed by tensile loading resulted in more damage, because of the “back-stress” associated with localized deformation surrounding the pores. Cracking took place primarily at the tips of the irregularly shaped pores in the microstructure, in both tension and compression, which was confirmed by microstructure-based finite element modeling. Cracking in compression was rationalized by the formation of a localized tensile stress at the pore tips, even under a far-field applied compressive stress.