Shock compression response of α″-Fe16N2 nanoparticles

The shock compression response of α''-Fe16N2 nanoparticles is studied in order to evaluate the thermo-mechanical stability of the α'' phase under shock loading. Shock compression experiments were performed using the parallel plate impact gas gun set up at velocities near 850 m/s. The experiments were performed at −21 °C and −126 °C in order to minimize temperature excursions and thereby determine the thermal effects on the phase stability. The α''-Fe16N2 phase is observed to partially decompose into α-Fe and γ'-Fe4N in both samples, as detected by the XRD analysis. The lower temperature produces a higher percentage of γ' phase in addition to the γ''-Fe50N50 phase. The pressure-volume-temperature response of the material is modeled using the dynamic mechanical properties of high nitrogen steel. The model is then used to evaluate the temperature excursions and their effect on the phase transitions observed.