Corrosion behaviour of resistance-spot-welded high-Mn austenitic TWIP steel

Abstract

High-Mn twinning-induced plasticity (TWIP) steels have been proposed to meet higher passenger safety and crash-safe vehicle frame requirements demanded by the automotive industry. The corrosion behaviour of welded Fe–30Mn–5Al–0.5C–6Cr TWIP steel using the resistance-spot-welding (RSW) technique was studied. Welds showed a microstructure consisting of primary austenite dendrites and interdendritic δ-ferrite in both fusion zone (FZ) and base metal (BM), which is in agreement with an austenitic-ferritic (AF) solidification mode. The results reveal that the refinement of the microstructure in the weld region does not significantly affect the corrosion resistance of this region, having a low corrosion current density of the order of 1 μA cm. It was concluded that Cr-rich second phase particles along the austenite/δ-ferrite interface can lead to Cr-depleted zones, increasing pitting corrosion susceptibility. It was found that the minimum Cr content at the Cr-depleted zones is nearly independent of the δ-ferrite volume fraction.