Abstract
The mechanism of intragranular nucleation of austenite in a duplex stainless steel (Fe-23.1 Cr-6.1 Ni-3.1 Mo-O.165 N-0.017 C, wt.%) weld metal and heat-affected zone (HAZ) has been examined. In the weld metal the acicular austenite is found to nucleate intragranularly on inclusions and subsequent plates form sympathetically resulting in a fine interlocked microstructure. Austenite plates adopt the Kurdjumov-Sachs orientation relationship with the ferrite matrix and grow with diffusion-controlled mechanism as evident from partitioning of substitutional alloying elements. At least one set of fine intrinsic dislocations on the austenite/ferrite interphase interfaces is observed suggesting that the boundaries are semi-coherent. The high cooling rates involved in the HAZ result in a supersaturated ferrite matrix where precipitation of intragranular austenite occurs as a result of reheating associated with subsequent passes. Austenite particles in the HAZ nucleate preferentially away from gain boundary austenite allotriomorphs indicating that intragranular precipitation is favoured by the supersaturated matrix.
| Original language | English |
|---|---|
| Pages (from-to) | 230-239 |
| Number of pages | 10 |
| Journal | Zeitschrift für Metallkunde |
| Volume | 82 |
| Issue number | 3 |
| Publication status | Published - 1 Mar 1991 |
Keywords
- precipitation metallography
- stainless steel
- welds
- aurami equation
- austenite ferrite interphase interfaces
- austenite nucleation
- duplex stainless steels
- intragranular nucleation
- Kurdjumov Sachs orientation
- iron and steel metallography
- heat affected zone