Resistance spot weldability of Fe-15.4Mn-2.1Al-1.2C twinning induced plasticity steel

Welding of twinning induced plasticity steels contains problems due to high manganese constituent. Low manganese and high carbon included twinning induced plasticity steels have not studied throughly in the literature. In this study, resistance spot weldability of Fe-15.4Mn-2.1Al-1.2C twinning induced plasticity steel was investigated. According to the results, interfacial, partial interfacial and pull-out type failure modes were obtained in tensile-shear tests. The maximum tensile-shear load was measured as 17.7 kN with 125 J ⋅ Ω⁻¹ heat input rate separated with pull-out failure. Although the heat affected zone was narrow, it formed the weakest region of the joint. Cleavage facets which is a sign of brittle fracture were detected on the fracture surface that formed in heat affected zone. A sudden increase in hardness supports the brittleness of the heat affected zone. Also, grain coarsening reduced strength of the heat affected zone. A narrow partially melted zone was identified between heat affected zone and weld nugget. According to electron back scatter diffraction phase distribution analysis, formation of manganese carbides was detected in the heat affected zone.