Ultrahigh strength ductile microalloyed steel with a very low yield ratio developed by quenching and partitioning heat treatment

Abstract

In this study, a microalloyed low carbon steel was subjected to quenching and partitioning (Q&P) heat treatment processes. The primary ferrite-pearlite microstructure of the steel was transformed into a bainitic microstructure containing interlath and sporadic blocks of retained austenite. The applied heat treatment process partitioned the carbon into the retained austenite to a weight percentage of 0.136. The microalloyed low-carbon steel acquired a continuous yield with high yield strength, a gigapascal level of ultimate tensile strength (i.e., ~ 1.1 GPa), and a very low yield ratio (i.e., 0.55) while retaining reasonable ductility and toughness when compared to the preheat-treated values.

Study of a Local Structure at the Interface between Corrosion Films and Carbon Steel Surface in Undersaturated CO2 Environments

“…γ-Fe is the precursor of α-Fe and Fe 3 C which form within the boundaries of austenite parental grains. However, it is known that the retained austenite can be present after a quenching process or through stabilization achieved in the presence of impurities. , The role of retained γ-Fe is still debated, but it has been suggested to be linked to fatigue crack initiation; however, other authors report benefits, , regardless, small but continuously increasing presence of amorphous γ-Fe and Fe 3 C is yet another indication of steel substrate degradation.…”

“…A mixture of γ-Fe and clusters of Fe 3 C aligned better with the PDFs (Figure S10b), although γ-Fe is only stable at temperatures between 915 and 1395 °C. 42 γ-Fe is the precursor of α-Fe and Fe 3 C which form within the boundaries of austenite parental grains. However, it is known that the retained austenite can be present after a quenching process or through stabilization achieved in the presence of impurities.…”