Insights on early recovery kinetics in ferrite - pearlite cold rolled high strength sheet steels

This study presents the results of temperature and composition dependent recovery behavior of ferrite-pearlite high strength steels. Annealing of cold rolled sheets at 300 °C with varying pearlite fractions results in an increase in hardness that scales with the pearlite content. In contrast, annealing at 500 °C results in a decrease in hardness, independent of pearlite content. By coupling complementary techniques such as high resolution nanoindentation mapping and electron microscopy (EBSD and TEM), microstructure-property correlations at the micrometer length scale are established to provide new insights on the driving force for temperature and composition dependent recovery kinetics. Simple recovery models are also discussed to complement the microstructural observations. Collectively, these results offer insights into the role of individual phases in the early recovery of ferrite-pearlite high strength steels that are critical for subsequent processing steps including inter-critical annealing. •High speed nanoindentation mapping to determine the hardness of ferrite & pearlite.•Ferrite-pearlite high strength steels show temperature dependent recovery kinetics.•Hardness increases during annealing at 300 °C due to Cottrell atmosphere formation.•Pearlite content dependent retardation of recovery at 300 °C.•Recovery at 500 °C follows Khulmann kinetics and is independent on pearlite content.