Effect of nanostructure on the mechanical properties of steel alloys / Sherif Ali Abdelrahman Ali ; Supervised Fawzya Kouta , Iman Elmahallawi , Taha Mohamed Mattar

Thesis (Ph.D.) - Cairo University - Faculty of Engineering - Department of Mechanical Design and Production

In this work, the nano structure has been attained in the studied steel through applying two different techniques. First methodology used is based on adding the nano sized inoculants particles to the molten of low carbon steel AISI 1020 (In ladle inoculation process). While, the second method is aimed at creating of nano sized bainitic structure of medium carbon steel by adopting the alloy's design, followed by low temperature isothermal transformation. For the in mould inoculation process SiC nano sized inoculant powders were added to the molten low carbon steel through specific ladle treatment technology. SiC provides a homogeneous dissociation in the metal matrix, generating of silicate inclusions that act as a nuclei for the grain structure causing the ductility increment. At the meantime, its dissociation acts positively on increasing the pearlite volume fraction, multiplying the tensile strength and the wear resistance properties. On the other hand, Si3N4 nano reinforcements were used as the second nano inoculants to the molten low carbon 1020 through ladle treatment process, aiming to replace the spheroidizing process in order to obtain spheroidized cementite. The existence of spheroidized cementite is desirable to before applying the severe cold rolling process. Si3N4 nano inoculant was used in order to nucleate the cementite, and modifying the morphology to a new globular cementite

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