Unveiling the Dual Mechanisms of Cerium in Suppressing Antimony‐Induced Hot Ductility Deterioration in C–Mn Steel: A Combined First‐Principles and Experimental Study

This study systematically investigates the mechanism by which cerium (Ce) mitigates antimony (Sb)‐induced hot ductility deterioration in C–Mn steel, an integrated approach of first‐principles calculations and experimental characterization. First‐principles calculations reveal that Ce exhibits a stronger grain boundary (GB) segregation tendency (segregation energy: −2.56 eV) than Sb (−1.15 eV) and S (−0.18 eV), enabling it to preferentially occupy GB sites. Experimental results demonstrate that adding 0.01–0.041 wt% Ce significantly enhances hot ductility, particularly in the temperature range of 800–850 °C, evidenced by shallower ductility troughs and increased reduction of area values. Microstructural analysis shows that Ce modifies inclusions from MnS/Al 2 O 3 to Ce–Sb–O–S complexes, thereby effectively immobilizing Sb. Electron probe microanalysis confirms that Ce addition reduces the GB segregation of Sb and S (with Sb enrichment decreasing from 3.55× to 1.78×) through both GB site competition and inclusion control. The dual mechanisms of Ce‐GB segregation and Sb immobilization in inclusions synergistically suppress Sb‐induced embrittlement. These findings provide crucial insights for optimizing the thermal processing of Sb‐containing recycled steels while improving their high‐temperature performance, holding significant implications for sustainable steel manufacturing.