M23C6 carbides and Cr2N nitrides in aged duplex stainless steel: A SEM, TEM and FIB tomography investigation
Abstract
The precipitation evolution during ageing of a 2101 lean duplex stainless steel was investigated, revealing that the precipitate type and morphology depends on the nature of the grain boundary. Triangular M23C6 carbides precipitate only at γ/δ interfaces and rod-like Cr2N nitrides precipitate at both γ/δ and δ/δ interfaces. After 15 min of ageing, the M23C6 size no longer evolves, whereas that of the Cr2N continues to evolve. For Cr2N, the morphology is maintained at γ/δ interfaces, whereas percolation occurs to form a continuous layer at δ/δ interfaces. By combining 2D and 3D characterisation at the nanoscale using transmission electron microscopy (TEM) and focused ion beam (FIB) tomography, a complete description of the precipitation evolution was obtained, including the composition, crystallographic structure, orientation relationship with the matrix phases, location, morphology, size and volume fraction. © 2016 Elsevier Ltd.
Keywords
- Stainless steel
- Aged duplex stainless steels
- Continuous layers
- Carbides
- Transmission electron microscopy
- Tomography
- Solvents
- Precipitation (chemical)
- Nitrides
- Morphology
- Ion beams
- High resolution transmission electron microscopy
- Nano scale
- Orientation relationship
- Nanotomography
- Crystallographic structure
- Lean duplex stainless steel
- Matrix phasis
- Grain boundaries