Increasing joint strength in magnesium-aluminum dissimilar impact welding by surface nanocrystallization of magnesium alloy sheet
Jianyue Zhang, Jianxiong Li, Jiashi Miao, Yu Mao, Xuejun Huang, Anupam Vivek, Glenn S. Daehn, Alan A. Luo
Abstract
While high velocity impact welding is perceived as a solid-state joining process, localized or continuous melting on the weld interfaces has posed a significant challenge. Here we propose to overcome this challenge by introducing a nanocrystalline layer on the metal surface for impact welding of magnesium to aluminum. After surface nanocrystallization, melting and intermetallic (IMC) formation at the interface were suppressed, resulting in a 60% improvement in Mg-Al joint strength. This is because the surface nanocrystalline layer limited the plastic shearing deformation and deformation heat at the Mg-Al interface during impact welding. Meanwhile, the high density of grain boundaries in nanocrystalline Mg layer and the high density of dislocations inside the nanocrystalline provided short-circuiting paths for Al diffusion into Mg matrix, forming a diffusion layer of 30–45 nm thickness. This work provides a new approach to dramatically improve dissimilar impact welding strength via surface nanocrysallization.