Precipitation Behavior of Cr ₂ N Phase in Lean Duplex Stainless Steel 2101 during Solution Treatment and its Influence on Mechanical Properties

To reveal microstructural evolution of lean duplex stainless steel (LDX) during heat treatment and further improve its mechanical properties, this study investigates the LDX 2101 through solution treatment at 950, 1050, 1150, and 1250 °C for 30 min, followed by tests about its microhardness and tensile properties. Results show that as‐cast LDX 2101 mainly contains α (matrix phase) and the dendritic γ. As the solution treatment temperature increases, morphology of γ phase transitions from coarse dendrites to discontinuous islands. The width of γ phase decreases from 47.30 μm (950 °C) to 18.25 μm (1250 °C), and the content reduces from 54.2% (950 °C) to 46.6% (1250 °C). After solution treatment at 950 °C, Cr 2 N phase precipitates and grows up at the interface between γ and α phases. After solution treatment at 1250 °C, many granular Cr 2 N phases also form within the matrix α phase. The main reason is that many N atoms diffuse from γ phase into α phase directly. And the diffusion distance increases continually with the increase of solution temperature. The yield strength, ultimate tensile strength, and elongation of LDX 2101 nearly reach their peak values (578.7, 670.8 MPa, and 40.1%) after solution treatment at 1050 °C.