Achieving high strength and ductility of multi-phase steel via hub-border architecture formed in 30 s

Abstract

The microstructural design utilizing heterogeneities from microscopic to atomic scales is an emerging solution beneficial for achieving extraordinary mechanical properties in hierarchy of metals. As the introduction of microstructural heterogeneities requires the alloying modification with high budget, and the conjugation of heat treatment and plastic deformation with multi-modes, the trade-off between mechanical properties and process effectiveness remains inevitable. Here, we describe a novel strategy for architecting the ‘hub-border’ constituent where rapid austenitization as well as rapid intercritical annealing at 300 K/s were imposed to harness the heterogeneity in term of carbon distribution. The final product shows a considerably higher fraction of martensite as compared to the sample produced using conventional way. Moreover, the bainite, which formed from the carbon-depleted austenite, working as border between hub martensite and ferrite plays two distinct roles in balancing strain misfit and strengthening interphase region to arrest the crack movement. The net result shows tensile ductility of 12 % with ultrahigh strength in excess of 1.5 GPa. Strikingly, such heterogeneities are attained in 30 s, which will serve industry-friendly microstructural perspective for high-performance structural candidates.