Abstract
Resistance spot weldability of martensitic stainless steels is impaired by the formation of brittle martensite in the fusion zone (FZ). In this paper, in situ rapid tempering via applying a second pulse current after a first melting/solidification pulse during resistance spot welding of AISI 420 martensitic stainless steel sheets was used as a pathway to enhance the toughness of the FZ. By using proper second pulse conditions, the FZ with reduced hardness can be generated which is featured by a decomposed martensitic structure with nano-sized carbide precipitations. The improved toughness as a consequence of this modified microstructure resulted in remarkable enhancement of the peak load and energy absorption of the spot welds compared to the single-pulse welds.
Disclosure statement
No potential conflict of interest was reported by the authors.
ORCID
Majid Pouranvari http://orcid.org/0000-0002-9603-447X
Hamidreza Aghajani http://orcid.org/0000-0003-1722-2251