Basic Science of Preparation: Transmission Electron Microscopy and Modeling of Copper and Aluminum Targets

摘要

This research involves an effort to study and compare the residual microstructures and dynamic behavior of two metallic targets of finite thicknesses, namely OFHC (oxygen-free high-conductivity) copper and 7039 aluminum, subjected to ballistic impact and perforation by a tungsten heavy alloy (WHA) projectile. Also included in this work is an attempt to validate mathematical modelling of experimental results through the use of a computer hydrocode, AUTODYN-2D, which allows for the simulation of ballistic penetration/ perforation events and possible differentiation of fundamental mechanisms through validation strategies. These targets represent two very different FCC materials. The 7039 aluminum is extremely hard in contrast to a softer, ductile copper. The 'failure' mechanisms appear to be different on a macroscopic scale, but may be similar on a microscopic scale. A preliminary investigation of the residual penetration channels in these two targets revealed significant microstructural differences. In the 7039 aluminum target there is a limited extent of microstructural deformation seen through optical microscopy, though numerous shear bands are observed near the channel wall and at the spalled region. Observations of the OHFC target, on the other hand, show a narrow region of recrystallized grains adjacent to the crater wall, beyond which is an extensive area of microband clusters. Similar features have been observed previously in connection with hypervelocity impact cratering in copper.