Effect of Al on the oxidation of grain boundaries during hot-rolled coiling of press hardening steel

Press hardening steel (PHS) is the most widely used material in automotive white bodies owing to its excellent formability and low springback. While replacing Ti with Al ensures the hardenability of PHS without compromising its toughness, grain boundary oxidation inevitably occurs during hot-rolled coiling. This phenomenon, driven by the oxygen affinity of alloying elements such as Si and Mn, adversely affects subsequent processing. Current research predominantly focuses on the mechanisms by which Si and Mn contribute to grain boundary oxidation, whereas the influence of Al has seldom been explored. In this study, tube-sealed heating was employed to simulate the hot-rolled coiling process, specifically investigating the effect of Al on grain boundary oxidation. The results demonstrate that Al inhibits grain boundary oxidation through the following mechanisms: Al reduces the oxygen adsorption rate at the scale/matrix interface, thereby lowering the oxidation rate; Al promotes decarburization and facilitates the enrichment of Si and Mn at the scale/matrix interface. This decarburization accelerates the dissociation of FeO, and the majority of the dissociated oxygen ions combine with the enriched Si and Mn at the interface to form oxides. Consequently, less oxygen enters the steel matrix.