Recrystallization in commercial grade interstitial-free steel, discussing criticality of martensite and massive ferrite nucleation along with mechanical property

Abstract

Interstitial-free steel is very soft and ductile, with a fully ferritic microstructure at room temperature. In order to address this issue in the present work, the cold-rolling increases tensile strength vividly by strain hardening. The heat-treatment thereafter optimizes strength-ductility, with an excellent combination, through fine recrystallized grains. The warm-rolled sample provides relatively an inferior property by partial recrystallization of the sample. Irrespective of unannihilated dislocations, both the samples after the recrystallization treatment in the austenitic domain at 925 °C, were water quenched in a laboratory scale to explore phase transformations additionally in the system. The microstructural characterization reveals that the nucleation of massive ferrite under rapid cooling requires austenite conditioning, similar to martensite in the alloy, constrained by strained lattice. The outcome fundamentally argues against the notion that the accumulation of crystal defects/dislocations promotes an extra driving force for a reconstructive phase transformation leading to massive ferrite.