Study on the Dissolution Behavior of Sigma Precipitate in Super Ferritic Stainless Steel Under Electropulsing Treatment

This study compares the effects of electropulsing treatment (EPT) and conventional furnace heat treatment on the microstructure and mechanical properties of a 27Cr–4Mo–2Ni super ferritic stainless steel preaged at 850 °C to precipitate the σ‐phase. The results show that EPT significantly accelerates σ‐phase dissolution, with complete dissolution achieved at 950 °C for 120 s, far more efficient than conventional heat treatment. Microstructural analysis reveals that EPT transforms the σ‐phase from a continuous network into isolated particles and eventual dissolution, driven by current concentration effects and electron wind force‐enhanced atomic diffusion. Mechanical tests indicate that although EPT specimens exhibit lower hardness (213–249 HV) than furnace‐treated ones (345–350 HV), they achieve a superior strength–ductility balance, with elongation reaching 22.7% compared to 18.7% for furnace‐treated specimens. Thermodynamic and kinetic analyses elucidate that pulsed current promotes σ‐phase dissolution by introducing additional electrical Gibbs free energy, lowering the dissolution barrier, and enhancing solute atom diffusion. This study demonstrates that EPT is an efficient and energy‐saving approach for microstructural control of super ferritic stainless steels, offering a novel pathway to mitigate performance degradation caused by brittle phase precipitation.