Formability and mechanism of pulsed current pretreatment–assisted laser impact microforming

Abstract

Pulsed current treatment was introduced into the laser impact microforming technology to improve the formability of laser impact forming. A pulsed current pretreatment–assisted laser impact microforming technology is proposed, and the formability and mechanism of such composite technology are discussed. In this study, the mechanical properties of H62 brass before and after pulse treatment were tested. The effect of pulsed current treatment on the formability of the material under high strain rate was studied by a laser impact free microbulging experiment. Moreover, the mechanism of pulsed current influence on the material’s formability was analyzed from the aspects of microstructure, texture evolution process, and grain size and morphology. Results showed that the elongation of the material was increased obviously, the flow stress during the tensile process was decreased significantly after pulsed current treatment, and the fracture form of the material gradually evolved from brittle fracture to ductile fracture. The forming height of samples under high strain rate improved greatly which may be due to the high-density pulsed current treatment that significantly alleviated the dislocation entanglement in the material. Owing to the weaker orange-peel effect which is induced by smaller recrystallized grains and lower maximum density of texture, the surface quality of formed parts after pulsed current treatment increased remarkably. In addition, the more uniform section thickness distribution of formed parts was observed, which may stem from obviously refined grains after pulsed current treatment improved the fluidity of the grains in a high–strain rate deformation process.