Mechanical properties and nanostructures in a duplex stainless steel subjected to equal channel angular pressing

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2012-08, Vol.551, p.154-159
• Main Authors: Chen, L., Yuan, F.P., Jiang, P., Wu, X.L.
• Format: Article
• Language: English
• Subjects: Applied sciences; Cross-disciplinary physics: materials science; rheology; Duplex stainless steel; Elasticity. Plasticity; Equal channel angular pressing; Exact sciences and technology; Materials science; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Mechanical property; Metals. Metallurgy; Nanostructure; Other heat and thermomechanical treatments; Physics; Treatment of materials and its effects on microstructure and properties
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2012.04.112

► Dual-phase nanostructure of austenite and ferrite was generated by ECAP. ► The yield stress of 1100MPa and uniform elongation of 7% was obtained. ► The response of strain hardening varies with the microstructure. The nanostructure and resultant mechanical property were studied in an UNS S32304 duplex stainless steel subjected to equal channel angular pressing. The successive refinement of original grains was observed to happen in dual phases, i.e., austenite and ferrite, during 4-pass pressing. Both phases exhibit similar lamellar features of microstructures by the formation of dislocation boundaries and their misorientation evolution with increasing strains. The deformation twinning and martensitic transformation as well were observed to happen in austenite. The transversal spacing of elongated grains is 79nm in austenite and 130nm in ferrite, respectively. After annealing at 973K for 20min, the elongated grains tend to become equiaxed, and the average size of nanograins increases to 108nm in austenite and 235nm in ferrite, respectively. The tensile tests show that the yield strength of the dual-phase nanostructure is 1460MPa after 4-pass pressing, as compared to 403MPa of its coarse-grained counterpart, but with uniform elongation of merely 2%. After annealing at 973K, the uniform elongation increases to 7% with the yield strength of 1100MPa. In addition, different stages of strain hardening were observed in various microstructures during tensile testing, and the corresponding plastic responses were discussed.