A strategy to introduce multi-gradient structures into iron by explosive shock wave processing

Abstract

A strategy combining shock-induced phase transition, twins, and dislocations to produce a multi-gradient structure in Fe is designed and proposed by the explosive processing method. A specific emulsion explosive is designed to introduce gradient pressure into iron ranging from 8.3 to 13.4 GPa by smooth particle hydrodynamics method. The pressure range generated by explosive processing covered shock loading phase transition point, shock unloading phase transition point, twin activating point and elastoplastic dislocation point of iron, creating gradient phase transition, gradient twins, gradient dislocations and gradient grain size structures in iron. The mechanism of gradient grain size formation is illustrated based on the twins and dislocation boundaries. Due to the multi-gradient microstructure, a demonstrating gradient hardness range from 1231.3 Hv to 89.8 Hv is distributed from the surface to the internal of the iron. This method lays an experimental foundation for Fe, Ti, Mg based gradient materials that undergo phase transition under low shock pressure.