Effects Of Electric Current Pulsing To The Nucleation Of Phase Transformation And Recrystallization Of Cu-Zn Alloy At Early Stage

With the development of modern society and the progress of material science, people’s demands for high-performance material is becoming more and more urgent, as a consequence, numbers of advanced methods in material properties improving has been developed to satisfy the requirements. For its impressive performance in property improving, electric current pulsing (ECP) treatment has been widely applied as one of the new material modification techniques.The current research fields about ECP include:grain refinement, electroplasticity, electron migration and healing of micro cracks, and so on. And the effects of ECP are greatly ascribed to the current density and electric pulse frequency. However, few investigations have been involved to investigate the effects of electric current on recrystallization nucleation and phase transformation nucleation. Especially, the effect of electric current direction on materials microstructures is still unknown, which limits the application of ECP on materials fields. To investigate the effects of current direction to phase transformation and recrystallization, the samples with the angles,0°,15°,30°,45°,60°,75°,90°, between current direction (CD) and rolling direction (RD) are applied in this study. Also the mechanism of the relationship between CD and the nucleation of phase transformation and recrystallization is discussed.The effects of electric current on phase transformaiton nucleation induced by ECP are investigated in a Cu-Zn alloy. The experimental results show that the inhomogeneous nucleation rate can be obtained due to different angle between CD and RD. For the samples with0°,45°,90°angles, the nucleation rates of α+β’â†'β phase transformation induced by ECP is lower than that of the samples with15°,30°,60°,75°angles. Further investigations on the αâ†'β phase transformation indicate that orientation relationship between a parent phase and β’sub-phase obeys K-S relationship. The coherent interface of αâ†'β phase transformation is the slip plane of a parent grain, which makes the possible24variants down to6variants during variant selection.The effect of electric current on recrystallization nucleation induced by ECP is investigated in a Cu-Zn alloy. For all the samples, the same single current density is applied during ECP treatment. By comparing the different microstructures obtained by EBSD, results show that recrystallization nucleation rate is higher when there is an angle between CD and RD. While for samples with CD parallel to RD, just the recovery can be observed. In addition, by detecting the texture evolution of the samples treated before and after ECP treatment, it can be found that the grain orientation distribution becomes more random after ECP treated. This phenomenon can be ascribed to the effect of electron wind force on recrystallization nucleation rate.