Experimental Research On5A90Al-Li Alloy Sheet Metal Forming Characteristics Under Electroplastic Effect

5A90Al-Li alloys are widely used in the aerospace industry due to low density,high specific strength, excellent specific stiffness, etc. They are considered to be themain structure materials of aviation aircraft in the21th century. However,5A90Al-Lialloys exhibit relatively low plasticity, which restricts complex parts formed atambient temperature. Therefore, many researchers have focused on forming propertyenhancement of Al-Li alloys using different methods. For instance, hot forming,incremental forming and electroplastic forming are developed. Among them,electroplastic forming is a good choice because of less production time, cost andenergy required. For the above shortcomings and studies, Experimental research on5A90Al-Li alloy sheet metal forming characteristics under electroplastic effect iscompleted. The main research content is as follows.The results of the room tension, electroplastic tension, and thermal tension of5A90Al-Li alloys show that the electropulsing can improve the elongation anddecrease the flow stress, yield stress, and the ultimate stress. Moreover, theelectroplastic effect is more obvious with increasing current. The effect ofelectropulsing on the elongation and flow stress was more obvious compared withthermal tension at the same temperature. The contribution to the elongation increaseand the flow stress drop resulted from the Joule heating and pure electroplastic effectwas calculated, and the results show the Joule heating plays a more important role inthe electroplastic effect.The microstructural variation of the room-temperature tension, electroplastictension and thermal tension was observed by SEM and TEM. Dimples weren’t foundin the fracture surface, which indicated the poor plasticity. Large numbers of dimplesappear in the fracture surface of thermal tension and electroplastic tension. Moreover, the dimples of electroplastic tension are deeper and larger than those of thermaltension which suggests the electroplastic tension can lead to better plasticity. Thedimples are larger and deeper with increasing current. Large numbers of dislocationsappear in the samples of room-temperature tension. Heating and electropulsing canboth decrease pile-ups, and reduce the density of dislocations. The electropulsing ismore able to decrease the density of dislocations compared with thermal effect. Theelectroplastic effect of5A90Al-Li alloys can enhance the mobility of dislocations,and induce their gliding and climbing, and reduce their density. The formingproperties of materials are improved when the denstiy of dislocatons is decreased.In the electroplastic bending and drawing experiments, the electropulsing caneffectively improve the plasticity, and avoid the appearance of cracks, and decreasethe yield stress and work hardening, and decrease the bending springback, andimprove the quality of the workpiece. The effect of improved quality resulted fromelectropulsing is more remarkable with increasing effective current. Theelectroplusing can improve the forming quality, and decrease the forming force.Moreover, the effect is more obvious with increasing effective current. Comparedwith the cracks at room-temperature drawing, the cross-part will be successfullydrawn to6mm when the effective current is168A, and the surface quality is excellent.