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Matls 701/702: Bita Pourbahari, PhD Candidate

Matls 701/702: Bita Pourbahari, PhD Candidate

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MS Teams - team code ffuvgr3

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materials@mcmaster.ca

Effects of Sb on the selective oxidation and reactive wetting of advanced high strength steels (AHSS)

Overview

Advanced high strength steels (AHSSs) are typically being subjected to an annealing process prior to galvanizing in continuous galvanizing line (CGL). During this process, commonly used alloying elements such as Mn, Si, and Al, due to having higher affinity for oxygen compared to iron, selectively oxidize. Presence of thick film-like oxides on the surface of steels can inhibit the formation of the required Fe2Al5Znx interfacial layer at the steel/bath interface, consequently, eliminate the chance of reactive wetting of the steel sheets during galvanizing. There are several methods which can be used to improve the reactive wetting of steels, such as the adjustment of the steel composition, controlling the partial pressure (pO2) of the annealing furnace gas atmosphere, the deposition of a thin layer of pure Fe, Ni, or Cu on the steel surface prior to annealing and the addition of surface-active elements to the steel chemistry. In the latter, minor concentrations (<0.1 wt.%) of elements such as Sn, Sb, and Bi are added to the steel composition as they are known to have high tendency to segregate to the steel grain boundaries and external surfaces during annealing, thereby changing the oxide interfacial energies and modifying the oxide morphology. This will result in a significant reduction in the selective oxidation kinetics.

The present study aims to determine the role of Sb micro-additions in AHSS steels to pave the way for further development of these alloys, which might broaden our understanding regarding oxidation and reactive wetting of steel alloys.