Influence of impact velocity on impact-initiated reaction behavior of Zr-Ti-Nb alloy

Reactive structural materials are of interest in military applications due to their impact-initiated characteristics. The determination of critical impact velocity is of crucial importance in designing munitions to produce a maximum destructive effect on the target upon impact. Here, combining high-speed photography and image processing technique, we demonstrate an approach to determine the critical impact velocity through quantitatively assessing the energy-release characteristics of a Zr-Ti-Nb reactive alloy under high-speed impact. The Zr-Ti-Nb alloy is fabricated by powder metallurgy and has high strength and sufficient ductility under dynamic loading. By conducting a series of ballistic impact experiments, the relationship between the impact velocity of alloy projectiles and light emission from burning fragments is obtained and discussed. Two critical impact velocities are determined. The first represents the minimum impact velocity required for initiating the intense exothermic reaction of the alloy projectiles, while the second denotes the impact velocity when the extent of reaction reached the maximum. By analyzing the fragments recovered at different velocities, it is proved that the fragmentation behavior of the alloy projectiles is found to be highly dependent on the impact velocity. This results in obvious different energy-releasing characteristics of Zr-Ti-Nb alloy, and the corresponding mechanism was also discussed.