Microstructural study of adiabatic shear bands formed by high-speed impact in a tungsten heavy alloy penetrator

The microstructures of adiabatic shear bands formed by high-speed impact in a tungsten heavy alloy penetrator were investigated in the present study. The penetrator was highly deformed at high strain rate by high-speed impact, and microstructural observation of the remained penetrator and the debris was conducted after the impact test. Heavily elongated tungsten particles and reaction products such as tungsten oxides were observed on the surface region of the debris presumably due to the local temperature rise occurring upon high-speed impact. A few adiabatic shear bands were observed in the regions near the surface cracks of the remaining penetrator, and their width was wide in comparison to the shear band formed in armor plates. The crack had general trends to propagate along the shear band, but sometimes changed its propagation path along the interfaces between adhering tungsten particles. It was suggested from the microstructural observation of the shear bands that in order to improve the penetration performance of the tungsten heavy alloy, the minimization of the tungsten–tungsten particle interfaces and the optimization of the fabricating process were required.