Experimental investigation of grain and specimen size effects during electrical-assisted forming

Alternative manufacturing processes such as hot working and electrical-assisted forming (EAF), which involves passing a high density electrical current through the workpiece during deformation, have been shown to increase the potential strain induced in materials and reduce required forces for deformation. While forming at elevated temperatures is common, the EAF process provides more significant improvements in formability without the undesirable effects associated with forming at elevated temperatures. This research investigates the effect of grain size and current density on annealed pure copper during the EAF process. The flow stress reduction effect of the process was shown to decrease with increasing grain sizes. A threshold current density, required to achieve a significant reduction in the flow stresses, becomes more apparent at larger grain sizes, and the value increases with increasing grain size. The effects increase with increasing strain due to dislocations being generated during deformation. Therefore, the dislocation density, related in part by the grain size, appears to be a factor in the EAF process. [DOI: 10.1115/1.4001039