Microstructural Refinement and Strain Hardening Behavior in Low‐Density Ultrafine Pearlite Steel

Advanced low‐density steels that meet energy shortages and high safety requirements have become a hot research topic in materials science. The addition of light elements with medium‐Al content (5 wt%) to ultrahigh‐strength pearlite cable steel alloy reduces the material density and causes a microstructural change from traditional θ‐pearlite (ferrite + cementite) to θ‐pearlite and κ‐pearlite (ferrite + cementite + κ‐carbide). The results show that the moderate addition of Al and Mn (5 wt%) promotes the formation of κ‐carbide, which inhibits the diffusion of C and significantly delays the eutectoid transformation process of pearlite. Meanwhile, the transformation free energy of pearlite increases and obviously refines the lamellar spacing of the ultrafine pearlite by κ‐carbide. Simultaneously, the interaction between κ‐carbides and dislocations is initiated, which increases the strain hardening rate of ultrafine pearlitic steel.