Estudo das transformações de fases das ligas Fe18Mn e Fe18Mn3Al laminadas a frio

Abstract

With the current need for optimization in steel consumption and processing, especially concerning cost reduction, this study investigated two alloys that have characteristics which could potentially replace maraging steels. The primary objective was to examine the influence of aluminum in a lean Fe18Mn alloy, aiming to reduce the fraction of ε martensite. Thereunto the microstructural behavior of two high-manganese alloys was investigated during cold rolling, the studied alloys content 18% in weight of manganese, and in one of them, 3% in weight of aluminum was added. The samples were processed by cold rolling, with reduction limits of 40% for Fe18Mn and 60% for the Fe18Mn3Al alloy. The results for the alloy without aluminum showed α’ and ε martensite in the as-received material, and as the thickness reduction increased during rolling, the fraction of α’ martensite also increased, exhibiting high hardness at all deformation stages. ε-martensite was present throughout the material's deformation until failure, and although the TRIP effect was dominant, it was not the only mechanism involved, as the TWIP effect was also observed. For the aluminum-added alloy, unlike Fe18Mn, the martensitic transformation was almost completely suppressed or at least slowed down, both ε and α’, although small regions of martensite were found, primarily at grain boundaries. Additionally, at higher strains, around 50%, the martensitic transformation influenced the material's hardness, and consequently, the TRIP effect began. The initial plastic deformation mechanism in the Fe18Mn3Al alloy was directly associated with dislocation slip and the TWIP effect, explaining the lower hardness compared to the Fe18Mn alloy.