Fractographic Features of Ultrafine-Grained Metals After Tension Accompanied by Pulse Current

The microrelief of samples of pure titanium and aluminum in single-crystal, coarse-grained and ultrafine- grained states subjected to tension accompanied by different modes of pulse current is studied using scanning electron microscopy. It is shown that the metals in all the states studied fracture by a ductile mechanism characterized by a dimple-cup fracture pattern. A common feature of the single-crystal and coarse-grained states is a microrelief bearing shear bands and large cups, while the ultrafine-grained state is characterized by dimples on the fracture surface. The dimple size does not correlate with the grain size but depends on the intensity of the pulse current and on the microporosity arising during the refinement of the structure.