High pressure treatment of iron by conically converging shock waves in a cylindrical capsule

A capsule, consisting of an inner iron rod as a sample and an outer 2024 aluminum alloy cylinder, was shock-treated. An iron flyer plate, 3.2 mm thick, was impinged on the capsules at an impact velocity of 2.2 km/s. The shock velocity in the cylinder is higher than that in the rod. This led to the formation of a Mach disk. The recovered sample was examined with an optical microscope. It was found that the grain size of the recovered sample is much smaller than that of a starting one. This means that the phase transition was induced by the propagation of shock waves. The recovered rod consisted of several regions, characterized by the respective metallographic features. These microstructures reflect shock compression history in the iron rod. In the cylindrical capsule, it was concluded that shock waves converge and interact to form the Mach disk in the iron rod.