Revealing the Mechanism of Ductility Discrepancy between Two 2205 Duplex Stainless Steels Containing Layered and Island Austenite Through In-Situ Tensile Test

Abstract

A notable discrepancy in tensile ductility was observed between two 2205 duplex stainless steels (DSS) containing layered and island-like austenite microstructures. The deformation behavior of both DSS 2205 was compared through in-situ Electron Backscatter Diffraction (EBSD) and Scanning Electron Microscope (SEM) techniques. The results indicated that the microscopic deformation mechanism for both DSS 2205 was governed by dislocation slip. The observed tensile ductility disparity was attributed to differences in dislocation slip behavior. In DSS 2205 with island austenite, slip transfer and blocking across grain boundaries occurred simultaneously, which was determined by the geometrical compatibility factor (m') calculations of adjacent ferrite and austenite grains. This intensified plastic inhomogeneities and promoted non-Schmid dislocation slip behavior. While in layered austenite of DSS 2205, the activation of slip system strictly adhered to the principle of maximizing the Schmid factor. Multiple slip systems in the ferrite on {110} and {112} planes were activated, inducing cross-slip, which enhanced ductility. The better ductility of DSS 2205 featuring layered austenite compared to the counterpart was further explained by quantitative analysis of geometrically necessary dislocations (GND) distribution in both phases and kernel average misorientation (KAM) values during deformation.

Keywords: 2205 Duplex stainless steel, In-situ EBSD/SEM, Slip trace analysis, Geometrical compatibility factor