The Metallographic Study of the Structure of Pestle Obtained from the Convergence of a Hemispherical Copper Shell

An experiment was carried out on the convergence of a copper shell, under the action of an explosion the shape of which is close to hemispherical, and a pestle in the form of a biconvex lens was obtained. An acute-angled protrusion about 2 mm high has formed on the front of the pestle. The macro- and microstructure was studied in the transverse and longitudinal sections of the pestle. It has been established that during explosive loading, spall pores are formed in the pestle. The pores are located in the front half of the pestle along the surface of the diverging cone. High-speed deformation during shell convergence occurs with the development of deformation bands 400–500 μm wide. The arrangement of the bands in the cross-section shows the flow directions during deformation. The bands consist of thin extended twins and small recrystallized grains. Recrystallization indicates an increase in the temperature to 500–600°C. The location of the deformation bands in the region of the protrusion shows that the protrusion represents the initial stage of the formation of a cumulative jet. Schemes of the shell convergence process are presented.