Developing a novel phase balance of duplex stainless steel for exceptional mechanical properties and corrosion resistance

The classical ferrite-austenite balance of duplex stainless steel is still challenged by fulfilling an ultimate balance between mechanical property and corrosion resistance. In this work, a novel phase-balanced metastable structure is in-situ developed using additive manufacturing via para-equilibrium transformation controlled by interstitial nitrogen diffusion. The novel phase-balanced structure comprises a primary fine equiaxed intragranular austenite, an incomplete partitioning of alloying elements, a predominate Kurdjumov-Sachs orientation relationship of ferrite/austenite interface and a high-density dislocation. Synergistic breakthrough of both mechanical property and corrosion resistance is endowed, where excellent yield strength is attributed to the high-density dislocation and the fine austenite, high ductility is facilitated by triggering stacking fault and kinking deformation from the dramatic increase of stacking fault energy, and extraordinary corrosion resistance is credit to the incomplete partitioning of alloying elements. This work expands the microstructure design framework for high performance materials.