Superior dynamic mechanical properties of high nitrogen austenitic stainless steel

Although high-nitrogen austenitic stainless steels (HNASS) exhibit superior properties over traditional austenitic stainless steels, their dynamic mechanical properties and corresponding microstructural evolution are rarely explored. In this study, dynamic mechanical properties of a novel HNASS, 10Cr21Mnl6NiN, are systematically investigated under the split Hopkinson pressure bar (SHPB) loading (1460–2830 s⁻¹ and 173–673 K) and plate impact (287–1990 ms⁻¹). An accurate Hugoniot equation of state is obtained. Compared with the typical austenitic stainless steel 316L (SS316L) with a similar texture and grain size, the Hugoniot elastic limit and spall strength of HNASS are $\sim$130% and 60% higher, respectively, and the dynamic yield stress at 2000 s⁻¹ is $\sim$150% higher due to nitrogen’s solid-solution strengthening in HNASS. The deformation mechanisms are strongly correlated with loading temperature and impact velocity. In the SHPB experiments, dislocation slip results in a $〈110〉$ texture along the loading direction regardless of the loading temperature. Besides dislocation slips, stacking faults, the Lomer–Cottrell locks and nano-sized $\left\{111\right\}〈112〉$ deformation twins are found at room temperature. Cryogenic temperature promotes the FCC to HCP phase transition. In the plate impact experiments, no newly formed HCP phase is identified, and $\left\{111\right\}〈112〉$ deformation twins are only found at high shock stress. For spall damage, intragranular voids are predominant, and coalesce into cracks. Given the quasi-static, SHPB, and shock compression data, a modified Johnson–Cook and Cowper–Symonds (JC$-$CS) constitutive model is established, which can well describe the mechanical behavior of HNASS over a wide range of strain rates.