Self-organization of adiabatic shear bands in ZK60 Magnesium alloy

Self-organization of shear bands in the ZK60 magnesium alloy was investigated by means of the radial collapse of the thick-walled cylinder technique. The distribution, the width, and the spacing of the multiple shear bands were examined under different effective strains. Optical microscopic examination showed the evolution of multiple shear bands was a competitive process, and influenced each other. The perturbation source such as precipitated phase and grain boundary can affect shear-band propagation, and leading to merging and bifurcation. The shear bands propagated along clockwise or counter clockwise direction at 45° or 135° with the radius from the internal boundary of the ZK60 cylindrical specimens, and exhibited approximately a symmetrical distribution pattern without obvious optimum selecting in direction. Results from an experimental investigation, the shear-band averaged width increased with the increase of the effective strain, varied between 3.83 µm and 9.87 µm with the effective strain varying from 0.57 to 0.88. The shear-band spacing was measured and compared with theoretical predictions in the frame of Grady-Kipp (momentum diffusion), Wright-Ockendon, and Molinari (perturbation) models. The results are closer to the theoretical predictions of the perturbation models, which indicated the shear-band spacing was determined by small perturbation of initiation, and interaction effect of multiple shear bands also cannot be ignored during the propagation process.