Enhancing the Delamination Toughening Effect by Tempering in the Hot Rolled Fe-4Mn-4Ni-3Al-0.1C Steel

Abstract

In this study, the delamination toughening mechanism of medium manganese steel (MMnS) study was investigated and enhanced this mechanism through tempering, resulting in a further improvement in impact toughness. Hot rolling at non-recrystallization region of austenite resulted in a lamellar configuration, which contributed to the initiation and propagation of the secondary cracks along the prior austenite grain boundaries (PAGB) to release the triaxial stress and achieve a delamination toughening. However, if secondary cracks connected to each other, delamination toughening failed. Austenite formed by inter-critical annealing (IA) was the key phase to hinder cracks connection. Moreover, through the precipitation and dissolution of carbides caused by tempering before IA, austenite with higher volume fraction and higher stability was formed at the PAGB than ones without tempering. Thus, tempering enhanced the delamination toughening in the whole temperature range.