Microstructural evolution and fatigue performance of dissimilar solid-state joints of SUS316L and SUS410

Abstract

Dissimilar stainless steels 316L (SUS316L) and SUS410 in a cylindrical butt configuration are solid-state joined along the cylinder axis by electrically assisted pressure joining (EAPJ). In EAPJ, different electric current densities are applied during compressive plastic deformation to investigate the effect of electric current density on joint performance. The microstructure analysis confirms that solid-state joints without macro- and micro-defects are fabricated through elemental diffusion and recrystallization during EAPJ. The effect of electric current density on the formation of martensite and subsequently on the variation of hardness is revealed by the grain average image quality maps and their relevant area distribution. The results of quasi-static tensile tests show that the fracture behavior of the joint is strongly affected by the applied electric current density. The fatigue behavior of joints with a higher tensile strength (SUS410 base metal fracture) is also evaluated by the S–N curve under a certain confidence level using two-parameter Weibull distribution. Finally, the fracture mechanism is investigated by examining the fracture surfaces from fatigue failure. The fracture morphology under high stress level exhibits a mixed fracture mode of base metal and interface fracture, while the fracture under low stress level exhibits interface fracture.