Dynamic mechanical properties and ignition behavior of TiZrHfX0.5 high-entropy alloys associated with temperature, trace element and strain rate

Abstract

High-entropy alloys (HEAs) have attracted much attention in the field of energetic materials due to their excellent mechanical properties, strong environmental adaptability and outstanding impact reaction energy release characteristics. The influence of temperature, trace element and strain rate on dynamic mechanical properties and impact ignition characteristics of TiZrHfCu0.5, TiZrHfNi0.5 and TiZrHfAl0.5 specimens were obtained. The ultimate strength of TiZrHfCu0.5 and TiZrHfNi0.5 specimens were significantly increased with the decreasing of temperature, while the toughness of TiZrHfAl0.5 increased at low temperature. Especially, ductile fracture mechanism of TiZrHfAl0.5 was mainly represented and the surface appeared ductile shear zone, and brittle and ductile dual fracture modes were represented in TiZrHfCu0.5 specimens during the process of deformation. However TiZrHfNi0.5 specimen underwent obvious brittle transition at low temperature. Meanwhile the ignition behavior showed a significant strain rate, trace element and temperature dependence. With the decreasing of temperature, the ignition threshold of TiZrHfNi0.5 decreased gradually. At the same temperature and strain rate, the duration and ignition severity were TiZrHfCu0.5, TiZrHfNi0.5, and TiZrHfAl0.5 from high to low, respectively. The ductile-brittle transition of the specimen at low temperature made the crack tip more prone to producing hot spots and induced stronger impact ignition reaction.