Metallographic, structural, and mechanical characterization of a low-density austenitic Fe-27Mn–8.5Al-1C steel microalloyed with Nb in as-cast condition

Austenitic Fe–Mn–Al–C low-density (LD) steels in the as-cast condition exhibit high hardness values due to the κ-carbide presence. Nb addition to LD steels generates grain refinement, solid-solution hardening, and carbide precipitation. The main objective of the present research work is to determine the Nb effect as a microalloying element on the microstructure and mechanical properties of an austenitic LD steel in the as-cast condition. For this purpose, Fe-27Mn-8.5Al-1C and Fe-27Mn-8.5Al-1C-0.25Nb (wt%) LD steels were fabricated by melting in a vacuum induction furnace. Metallographic characterization was performed by LOM and SEM–EDS. The primary and secondary phases were identified by XRD. Finally, to determine the mechanical properties, Vickers microhardness tests were carried out. In general, both steels showed a dendritic solidification microstructure with austenite grains, δ-ferrite islands, and κ-carbide. The Nb-microalloyed LD steel presented a slight increase in hardness with a greater degree of grain refinement compared to the non-microalloyed steel.