Identificação de fases em ligas do sistema Fe-Al-Nb-C por técnicas de caracterização de materiais

Abstract

The increasing demand for materials with high mechanical strength, thermal stability, and low density has driven the development of advanced metallic alloys for sectors such as the automotive and aerospace industries. Microstructural control is essential, as the presence and distribution of intermetallic phases and precipitates directly influence the material's properties. Therefore, detailed microstructural characterization, using techniques such as Transmission Electron Microscopy (TEM), becomes fundamental, especially for complex alloys such as those in the Fe-Al-Nb-C system. In this work, initial analyses were carried out using Scanning Electron Microscopy (SEM) to evaluate the morphology of the phases and to obtain an overview of the microstructure of the as-received samples. Based on the results obtained, specific regions were selected for the preparation of ultrathin lamellae by Focused Ion Beam (FIB). These lamellae were then analyzed by TEM, with the acquisition of High-Resolution TEM (HRTEM) images, localized chemical analyses via Energy Dispersive X-ray Spectroscopy (EDS), allowing for the semi-quantitative identification of the chemical composition in regions of interest, and interplanar distance measurements aimed at the crystallographic identification of the phases present. This combined approach enabled a comprehensive microstructural investigation, integrating information on morphology, composition, and crystalline structure, allowing for the identification of phases such as kappa carbide (κ) and cementite (Fe₃C) among those present.