Abstract: Equilibrium phase diagram and element content changes in precipitated phases of a novel high-strength austenitic stainless steel were calculated based on Thermo-Calc thermodynamic software. At the same time, the types of precipitated phase in the solution treated steel were determined by SEM and TEM, and the precipitation temperature and amount of the precipitated phase were calculated when the contents of C, Nb, V, N, Ni, Mo, Cr and Mn elements in the steel changed. The results show that after solution treatment, the precipitated phases in the steel are mainly large-sized rod-shaped precipitated phases and fine spherical precipitated phases, both of which are Z phases. The Z phase is primarily affected by C, Nb, V and N elements. As the content of C and V increases, the precipitation temperature of the Z phase decreases. As the content of Nb and V increases, the amount of Z phase precipitation increases. Conversely, as the content of N increases, the amount of Z phase precipitation decreases. The Ni, Mo, Cr, and Mn elements have a relatively minor impact on the precipitation of the Z phase. Considering the solution strengthening and precipitation strengthening effects of elements in the material, as well as their impact on grain boundary corrosion, within the composition range, C, Nb and N elements are the key focuses for optimizing the composition of the steel.

Key words: high-strength austenitic stainless steel, thermodynamic calculation, equilibrium phase diagram, precipitated phase