Grain Boundary and Microstructural Characterization of Heat-Treated As-Rolled 2205 Duplex Stainless Steel

The detrimental precipitation at the 2205 duplex stainless steel (DSS) grain boundaries has characterized the material to have poor workability after being hot-rolled. However, the detrimental precipitation in the microstructure is largely influenced by the cooling rate or method. There is an insufficient investigation of this steel's grade interfaces and grain boundaries to rationale its poor workability. This study investigates the influence of heat treatment of hot-rolled 2205 DSS to eliminate the precipitation at the grain boundaries and a detailed microstructural study. The procedure was carried out by heat-treating the as-rolled 2205 DSS to achieve the equiaxed and Widmanstätten austenite morphologies. The characterization was conducted using an optical microscope, electron backscatter diffraction and X-ray diffraction. It was found that the Widmanstätten morphology carried a high fraction of austenite-ferrite interfaces and high grain boundary responsible for the steel cracking during hot rolling. The SEM analysis observed an incoherent interface in Widmanstätten morphology, while the equiaxed demonstrated a coherent interface. XRD detailed new phases such as martensite and cementite in Widmanstätten and equiaxed morphologies, respectively. The Widmanstätten will quickly be susceptible to crack initiation under the application.