Passing one electric-current pulse through deformed pearlitic steel wires at room temperature causes the formation of cementite particles around 30 nm in size. This is found not only in some particular locations but throughout the cementite area, which reveals a different mechanism from traditional spheroidization of cementite plates because the latter leads to the formation of particles with much large size. Transmission electron microscopy images show electropulse-induced strain relief and formation of fine precipitations. Differential scanning calorimetry analysis demonstrates the additional stored free energy by electropulsing treatment. The raised free energy accounts the increased interface area in finer microstructure of materials. The experiment evidences that the passing electric current in metal has alternated the free energy sequence of various microstructures in comparison with that of current-free system.