Effect of punch type on microstructure and mechanical properties of aluminum alloy structures prepared by electromagnetic riveting

In this work, a special electromagnetic riveting punch with a convex die was proposed to improve deformation uniformity of rivets. Electromagnetic riveting experiments with the special and conventional flat punch were employed to contrastively investigate microstructure evolution and mechanical properties. Results showed that the width of adiabatic shear bands in the flat headers was narrower than that in the concave headers. The deformation uniformity of the concave headers was better. Microhardness distributions in concave rivet headers were more uniform than that in flat rivet headers. The plastic flow toward rivet hole was larger for the concave headers, resulted in a greater interference-fit strengthening effect of riveted structures. The difference in shear loads of riveted structures with the flat and concave headers was not significant. The riveted structures with concave headers had better vibration absorption effect. The shear friction effect on the fracture surface was more pronounced. The maximum pull-out loads of riveted structures with the flat and concave headers were respectively 13.4 kN and 13.9 kN, showing that riveted structures with concave headers had good resistance to pull-off. By changing the geometric shape of the punch, the quality of the riveted structures has been improved.