Constitutive Flow Equation for Cast Austenite–Ferrite Stainless Steels

Cast duplex (austenite–ferrite) stainless steels are important materials in many domains. Their mechanical properties are altered by thermal aging. The demonstration of the mechanical integrity requires the assessment of the mechanical behavior before and after aging. In this work, we focus on the identification of the relevant microstructure parameters controlling the behavior of the unaged materials, which allows later to track the effect of aging temperature and time on these parameters. We propose an analytical flow equation obtained by integration of the Kocks–Mecking constitutive equations in ferrite and in austenite. The macroscopic behavior is assumed to obey a simple mixture rule of the two phases weighted by their respective volume fractions. The close agreement with many tensile curves, obtained at different temperatures on different duplex steels, suggests that the behavior of the unaged cast Duplex stainless steels is determined only by the volume fraction of ferrite, with no significant effect of the chemical composition.