Fe-7.1Al-0.7Mn-0.4C-0.3Nb alloy microstructural characterization from Fe-Mn-Al-C system

In recent years, several studies have been carried out seeking to reduce the weight of motor vehicles to reduce pollutant emissions. In this scenario, low-density steels from the Fe-Mn-Al-C system can be considered a promising alternative to meet these requirements of the automotive industry. Generally, in low-density steel, a considerable aluminum amount is added in order to reduce the overall density of the steel. However, high aluminum contents promote distinct characteristics in the microstructure of these steels when compared to conventional steels, such as the k carbide presence ((Fc,Mn)(3)AlC), in addition to the need to understand the combination of this element with other alloying elements that can be added. In this context, this paper aims to evaluate the resulting microstructure, hardness and density as a function of the Al and Nb influence in a new chemical composition belonging to the Fe-Mn-Al-C system, in hot worked condition from X-ray diffraction and eletron microscopy analyses, hardness, and density measurements by Archimedes' principle. The results indicated that the high added Al promoted a reduction of about 13% in density, in relation to typical structural steels. and the delta ferrite stability up to room temperature. The condition evaluated at room temperature presented a microstructure formed by a matrix with delta and alpha ferrite. together with k-carbide (AlFe3C) and niobium carbide (NbC) precipitates, the latter two due to the Al and Nb additions. resulting in 59.4 +/- 1 HRA hardness and an estimated tensile strength limit close to 800 MPa - within the range of the Advanced High Strength Steels (AHSS).