Shock-induced phase transformation and vortex instabilities in shock loaded titanium alloys

Spall-tests of four kinds of high-strength titanium alloys (VT-6, VT-14, VT-20 and VT-23) have been performed by using a two-channel velocity interferometer for recording free surface velocity profiles and a SEM-technique for microstructure investigations of post-shocked specimens. Screw rotational structures in the spall zone are thought to be responsible for the more effective shock-wave energy scattering during spallation. Free surface velocity profiles display forward alpha --> omega and reverse omega --> alpha phase transitions in the all alloys under investigation. The threshold stress for the forward and reverse phase transitions turns out to be practically independent of the chemical and phase compositions of specimens, and monotonously increases with strain rate.