Nitrogen partitioning between matrix, grain boundaries and precipitates in high-alloyed austenitic steels

Abstract

New high-interstitial austenitic Fe–19Cr–22Mn–1.6V–0.4C–0.8N (mass. %) and Fe–22Cr–26Mn–1.3V–0.7C–1.2N steels were designed. A combination of high interstitial content (C + N = 1.2 mass. % and C + N = 1.9 mass. %, C/N = 0.5–0.6) and V-alloying of these steels provides a complex hardening mechanism (a solid-solution hardening, a particle strengthening and a grain boundary hardening). Increase in solid-solution temperature in the interval 1100–1230 °C forces solid-solution hardening, causes grain growth and changes a distribution and volume fraction of the precipitates in austenite. The relation of these factors governs the value of a yield strength, an ultimate tensile strength and an elongation in the high-interstitial steels. The variation in particle strengthening with solid-solution temperature has minor effect on the yield strength of the steels, but the distribution of precipitates strongly influences a tensile fracture micromechanism of the steels. The effect of solid-solution temperature on fracture peculiarities is described based on microstructural analysis of the steels.