The time-temperature-precipitation (TTP) and corresponding mechanical properties in high-nitrogen austenitic Fe-18Cr-18Mn-2Mo-0.9N steel (all in weight percent) were investigated using electron microscopy and ambient tensile testing. The precipitation reactions can be categorized into three stages: (1) high-temperature region (above 950 °C) - mainly coarse grain-boundary (intergranular) Cr2N; (2) nose-temperature region-intergranular Cr2N → cellular Cr2N → intragranular Cr2N + sigma (σ); and (3) low-temperature region (below 750 °C) - intergranular Cr2N → cellular Cr2N → intragranular Cr2N + σ + chi (χ) + M7C3 carbide. After cellular Cr2N precipitation became dominant above 800 °C, yield and tensile strength gradually decreased, whereas elongation abruptly deteriorated with aging time. On the contrary, prolonged aging in the low-temperature regime increased tensile strength, caused by the precipitation of fine χ and M7C3 within grains. Based on the analyses of selected area diffraction (SAD) patterns, the crystallographic features of the second phases were analyzed.
|Number of pages||10|
|Journal||Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science|
|Publication status||Published - Dec 2006|
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Mechanics of Materials
- Metals and Alloys