| Abstract Scope |
Initially, the Al-added medium Mn steel (Fe-7.92Mn-2.7Al-0.88Si-0.21C) was developed by melting casting route in an open-air induction furnace. Further, the developed alloys in hot rolled condition have been laser welded in butt joint configuration to investigate their weldability. Microstructure characterization and mechanical properties of the welded joint have been investigated by optical microscopy, scanning electron microscopy equipped with energy-dispersive spectroscopy, electron back-scattered diffraction spectroscopy, micro and nano hardness test, and tensile test. Further, the porosity in the weld zone was measured using Micro-CT. The result shows that the Al added medium Mn steel has been successfully welded in a butt joint configuration by laser welding. The fusion zone contains dendrites of athermal fine lath martensite in a ferrite matrix due to rapid cooling. However, the presence of some traces of very fine austenite in between the fine lath martensite in dendritic structure has been confirmed by EBSD analysis. Microstructural analysis shows some shrinkage porosity inside the dendritic structure in the fusion zone, but it didn’t affect the mechanical properties of the welded joint. The welded joint exhibits 100% strength efficiency (ratio of welded joint strength to base metal strength), but the total elongation has been reduced to ~25% compared to base metal elongation (~40%) due to the formation of the hardened zone in gauge length. Further, the post-welded heat treatment of the welded joint was done at 450, 550, and 650 ℃ for 60 minutes duration to analyze the effect of heat treatment on microstructure and mechanical properties. The heart treated at 650℃ shows the complete transformation of martensite into ferrite and austenite in the weld zone. |