EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Non-metallic inclusions such as oxides are commonly present in all steels as a result of steelmaking processes. These inclusions are important because they influence the mechanical properties of the material. Current knowledge concerning compositions, formation and growth mechanisms of inclusions in steel is rather well-established; however, their intrinsic mechanical properties are less well understood. In this work, micromechanical tests are conducted on spherical micron-scale silica inclusions contained within ferrous samples, which were produced by melting oxygen-containing iron under controlled conditions and adding silicon as a deoxidizer. Nanoindentation experiments performed on polished flat surfaces are conducted to evaluate their stiffness and hardness. Along electrochemically polished surfaces partially exposed inclusions are notched using a focused ion beam to produce “C-shaped” microscopic test samples, which enable measurements of their intrinsic resistance to tensile stress, free of micromachining artefacts, once data are coupled to bespoke finite element models. Data reveal that the silica inclusions in iron or steel can have intrinsic fracture strengths as high as 8 GPa.