| About this Abstract |
| Meeting |
MS&T24: Materials Science & Technology
|
| Symposium
|
Austenite Formation and Decomposition V: A Symposium in Memory of Prof. Mats Hillert
|
| Presentation Title |
Extremely Low Cooling Rate Austenite Decomposition in FeNi Iron Meteorites |
| Author(s) |
Frederic Danoix, Raphaële Danoix, Jérome Gattacceca, Clara Maurel, Mathieu Roskosz, Matthieu Gounelle, Mohamed Gouné |
| On-Site Speaker (Planned) |
Frederic Danoix |
| Abstract Scope |
Miles away from standard austenite decomposition in steels, the transformation of austenite in iron meteorites takes place at extremely slow cooling rates, partly in full equilibrium conditions. Iron meteorites are Fe-Ni (P) alloys that cooled down from the melt at rates of kelvin(s) per million year. With an initial austenitic grain size as large as a few meters, most of the observed transformations are intragranular. During cooling, below about 800°C, austenite transforms to ferrite, leading to the iconic Thomson-Widmanstätten pattern. At lower temperatures, typically 500°C, atomic diffusion is reduced, and a decreasing Ni gradient forms in austenite from the α/γ interface. Local Ni enrichment stabilizes austenite at lower temperatures, allowing the formation below 325°C of a fcc L10 ordered equiatomic Fe-Ni phase, called tetrataenite. This phase attracts huge interest, due to its outstanding magnetic properties, making it a potential rare earth element free permanent magnet. |