Investigating Optimum Hot Working Window of 2205 Duplex Stainless Steel Using Modified Dynamic Material Modeling

Abstract

This paper uses a modified dynamic material modeling (MDMM) suggested by Murty and Rao to develop processing maps (PM) of 2205 duplex stainless steels (DSS). Gleeble 1500D, a thermo-mechanical simulator was used to conduct single hit compression tests at a temperature between 850 and 1050 °C and strain rates of 0.001-5 s⁻¹. Additionally hot compression tests at a strain rate of 15 s⁻¹ and same temperature range were also conducted on a Bahr 805 dilatometer. As per general procedure acquired stress-strain data were corrected for friction and adiabatic heating, before constructing PMs at true strains of 0.1, 0.3, 0.5 and 0.8. Microstructures to validate the PM were prepared from safe domains and instability regimes belonging to PM of 0.8 true strain. Results showed that hot processing at intermediate to high strain rates and temperature leads to formation of flow instabilities such as mechanical twins and adiabatic shear bands. Safe domain located within the temperature range of (850-925) °C, strain rates of (2.6-15) s⁻¹ and peak η = 35% gave an inhomogeneous microstructure with presumably non-uniform mechanical properties. This region was considered ideal for hot processing of 2205 DSS provided that deformation conditions are carefully controlled to optimise DRX. Low Z conditions also provided an optimum hot working for hot processing.