Microstructure evolution in metals induced by high density electric current pulses

In this paper, microstructure evolution in metals induced by high density electric current pulses (ECPs) treatment, such as grain refinement, formation of oriented microstructure and redistribution of inclusions, is carefully reviewed. The mechanism for these microstructure evolutions is discussed. It is suggested that there are usually several factors working during ECP: Joule heating (including temperature rise, the heating rate and the cooling rate), stress (including thermal compressive stress, skin effect, electron wind force) and free energy change caused by the current. The Joule heat and the stress usually affect the dynamics, enhance the microstructure evolutions rate, while the free energy change affects the thermodynamics and lowers the barrier of the phase transformation or recrystallisation. The experimental results indicate that high current density ECP provides an effective approach to refine the microstructure of polycrystalline materials and to improve the mechanical properties of the materials.