Figure 3.

The surface microstructure of the residual projectile. (a) Microstructure of longitudinal section of residual projectile nose. There are two distinct zones: the microstructure inside the projectile almost unaffected by friction heat, while the microstructure near the surface of the projectile becomes denser. (b) Microscopic observation of the surface of the projectile nose by metallographic microscope. Many parallel and long grooves distributed on surface of the projectile nose.