An explosive impact technique to nanocrystallize and harden surface of metal materials

Z. Tong, Z.M. Shi, S.J. Tong
Inner Mongoli University of Technology, CN

Keywords: severe plastic deformation, nanostructure, surface, steel, copper, explosive impact

Summary:

An explosive impact surface nanorisation technique (EISNT) was developed to prepare nanostructured surface layers on medium carbon steel (MCS) and pure Copper (PC) plates. The plastic deformation involved the entire plate depth of 4-6 mm, and the sandwich structures were produced perpendicular to the impact direction. Nanocrystal layers with a thickness of 30-50 μm were produced; the granularities were reduced to approximately 10 nm for both metal plates. The surface microhardness was increased from 130HV to 475 HV for the MCS and from 70 HV to 160 HV for the PC respectively. An amorphous structure was formed around the nanocrystals in the MCS and the cementite flakes within the pearlite appeared along the slip, segmentation and fracture during the plastic deformation. The nanocrystallization and amorphous structures in the impact surface was ascribed to the adiabatic shearing band, dynamic recrystallization and rapid solidification of the melted layer. In contrast, the nanocrystallization was ascribed to the dislocation walls (DDWs) and dislocation tangles (DTs) in the PC.