Thickness-Dependent Microstructure and its Effect on Anisotropic Mechanical Properties of Duplex Stainless Steel 2205 Multi-pass Welded Joints

In this study, the thickness-dependent microstructural characteristics of duplex stainless steel 2205 multi-pass welded joints were first investigated by the combination of optical microscope and electron back-scattered diffraction observation. Subsequently, a series of tensile tests of miniature samples cut from different passes and directions were performed to analyze the thickness-dependent and anisotropic mechanical properties. The results demonstrate that the microstructure changed with the welded passes, i.e., a large number of grain boundary austenite, Widmanstätten austenite and a small number of tiny intragranular austenite existed at the surface passes, while a mass of intragranular austenite were found at the middle passes. Meanwhile, the Kurdjumov–Sachs orientation relationship was widespread at the welded zone. In addition, the yield and tensile strengths of the middle passes were greater than that of the surface passes due to the grain-boundary strengthening by tiny intragranular austenite. Furthermore, due to the existence of Kurdjumov–Sachs orientation relationship, the longitudinal yield and tensile strength were greater than transverse values, particularly for the middle passes.