Simulation and analysis of the solidification characteristics of a cast austenitic stainless steel
G. Aktaş Çelik M. I. T. Tzini Ş. H. Atapek Ş. Polat G. N. Haidemenopoulos
AbstractIn automotive applications, especially in exhaust systems, cast ferrous materials (cast iron, stainless steels, mild or carbon steels etc.) are preferably used due to their excellent mechanical properties, creep, oxidation and corrosion resistance at high temperatures. In diesel and gasoline engines, the manifold materials are subjected to 950°C, at which cast austenitic stainless steels (CASSs) are preferred due to their superior physical and chemical properties. The desirable properties of CASSs are basically determined by their as cast microstructures, hence it is important to identify the solidification path revealing out the microstructural features, stability of the phases and elemental partitioning during all phase transformations. In this study, a Nbstabilized Fe-Cr-Ni austenitic stainless steel was selected as an candidate alloy for exhaust manifold material. Both its solidification behavior and microsegregation were investigated using thermodynamic calculations by Thermo-Calc. The studied composition was also cast and thermal analysis studies were carried out in order to reveal the sequence of phase formation and the phase transformations during solidification. The present study not only consists of thermal modeling and analysis but also determination of matrix phases by using microscopy. The data obtained will be useful to understand the high temperature behavior of the studied alloy.