Wallner lines in a nanocrystalline Ni–23% Fe alloy

Wallner lines and their variants were observed for the first time in a nanocrystalline Ni–23% Fe alloy. The physical nature of the Wallner lines and their variants were analyzed by investigating the mechanical response, deformation and fracture mechanism of the nanocrystalline Ni–23% Fe alloy. It was concluded that the Wallner lines and periodic fracture markings were results of the strong external stress wave effect combined with a specific degree of plastic deformation and crack microbranching.