Ultra-high-speed deformation by impact of a projectile flying at speeds on the order of km s−1

An apparatus was developed to facilitate application of an electro-thermo-chemical accelerator to high-speed deformation experiments. The apparatus is designed on the principle of sequential collision of elastic bodies. Speeds ranging from 600 to 780 m s−1 were achieved, and estimated strain rate of deformation is 107 s−1. The newly developed apparatus can be applied to various types of accelerators for attaining deformation speeds as high as several km s−1. Transmission electron microscopy of aluminum deformed at high speed by use of the apparatus revealed the formation of very small stacking fault tetrahedra (SFTs). This observation is quite new for aluminum; previously, SFTs had not been observed in aluminum, although deformation had been carried out at strain rates lower than 106 s−1. Use of the apparatus promises to provide new insight into high-speed deformation.