[en] This study was undertaken to investigate the influence of predeformation in rotary swaging strain induced melt activation (SIMA) process on the microstructural characteristics and mechanical properties of C5191 copper alloy. In this paper, plastic energy was utilized as an indicator to assess the value of stored energy in materials. The plastic energy of rotary swaging (RS) under different conditions was calculated by numerical simulation using FORGE 3D software and integral equations. The results showed that the plastic energy of RS was only related to the billet radial strain, and the plastic energy of each pass reduced with the increasing of the RS passes number. The twinning and dislocation distributions in the rotary swaged materials and semi-solid materials were analyzed by the electron backscatter diffraction technique. These results illustrated the migration of high-angle boundaries were migrated and defects were removed during recrystallization. Semi-solid C5191 alloy were prepared under different radial strains. It was found that the increase of plastic energy, decrease the spherical grains formation duration. Meanwhile, the high plastic energy promoted the refinement of spherical grains, the reduction of neck-grains number, and the enhancement of hardness. - Highlights: • Globular microstructures formation mechanism of RSSIMA process is recrystallization. • Effects of billet radial strain and die speed on plastic energy were studied quantitatively. • Larger plastic energy contributes to the grain sizes refinement and materials Vickers hardness improvement during IHT.