Excellent dynamic yield and spall strength of single crystal NiAlCo alloy under shock compression

Abstract

A fundamental understanding of the mechanical behaviors and deformation mechanism of materials subjected to dynamic loading is critical for developing outstanding structural materials. This work focuses on the experimental investigation into the dynamic mechanical behaviors, deformation mechanisms, and damage characteristics of single-crystal NiAlCo which was regarded as a potential structure material at high pressure and strain rate. The shock responses of the single-crystal NiAlCo alloy were tested over a range of shock pressure from 10 to 50 GPa at a strain rate of 10⁵/s utilizing the technique of magnetically driven high-velocity flyer plates on high pulsed power generator CQ-4. Based on the analyses of free surface velocity profiles, a linear Hugoniot relationship between shock wave speed and particle velocity was obtained, and the spall strength gradually increased from 2.61 GPa to 6.98 GPa with increasing shock pressure. The yield strength was calculated from the Hugoniot elastic limit, and it reaches 1.80 GPa over the wide range of shock pressure. Further, the relationship between dynamic strength and strain rate was depicted by empirical formulas in power exponential form. Finally, the detailed transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) microscopic characterization results of recovered samples disclose that single-crystal NiAlCo have abundant micro-deformation mechanisms under high pressure and high strain rate, including dislocation tangle, high-density stacking faults, and Lomer-Cottrell locks. The results show that both spall and yield strength are significantly higher than those of most alloys, exhibiting superior mechanical properties, which may be attributed to the coupling of multiple deformation mechanisms.