Superior Strength and Ultrahigh Ductility in Hierarchical Structured 2205 Duplex Stainless Steel from Nanoscale to Microscale

Abstract

A laminated structured 2205 duplex stainless steel (DSS) with graded grain size was prepared via aluminothermic reaction and subsequent hot rolling with deformation of 80% at 1000°C, and its mechanical properties, strengthening and toughening mechanism were studied. Our materials have extraordinary elongation of 54% and high tensile strength of 990 MPa. The lamellar structure is characterized with heterogeneous lamella austenite (with nano-grain, ultrafine grain, micro-grain and nano-twin) and ferrite (with ultrafine grain and a proper amount of micro grain) coalesced alternately. The high strength is attributed to strengthening of complex grain (distribution from nanoscale to microscale) and interfaces arising from hierarchical and laminated dual-phase heterogeneous structure and distribution. The unusual high ductility is thought to be mainly attributed to the lamellar structure and dislocation hardening.

Fig. 4 The hierarchical 2205 stainless steel and conventional 2205 stainless steel: (a) tensile engineering stress-strain curves; (b) representative true stress-strain curves form (a). Inset exhibits the strain-hardening rate (Θ)-true strain curves; (c) strength-elongation plot of selected duplex stainless steels.