Improved uniform ductility in a high-carbon pearlitic steel via microstructural homogeneity architecture

In this work, the nucleation and growth kinetics of pearlitic transformation are quantitatively investigated to unveil the distinctive microstructural evolution behavior under a high undercooling degree. Both intra-granular and inter-granular nucleation increasingly occur with 1-2 orders of magnitude increase in nucleation rate N˙. However, a moderate increase in the growth rate GV, namely a larger N˙/GV ratio, leads to a 30%–40% size reduction in pearlitic colonies. The avalanche-type increase in nucleation events induces a more random distribution of ferrite orientation among colonies that possess a slight increase in relative misorientation but a pronounced increase in accumulative misorientation, and an arbitrary alignment of Fe3C lamellas in colony interior. Such improved microstructural homogeneity ensures more uniform and localized deformability, which allows compatible deformation between colonies or within colonies and prevents the expansion of newly-formed cracks. These results provide guidance for industrial manufacture of high-carbon pearlitic products with high safety and reliability, resulting from the improvement in localized deformability, and for low-cost wires via reducing the drawing passes, stemming from the significant increase in uniform deformability.