Abstract
The transformation kinetics of austenite to ausferrite for five ductile cast irons during the austemperign between 280 and 420 °C has been studied. Using dilatometry data, the kinetic parameters n and k of the Johnson-Mehl model, were determined. The activation energy was determined using the Arrhenius equation. The microstructure of samples austempered at 370 and 315 °C was observed by transmission electronic microscopy. It was found that the k constant decreased when copper and molybdenum were added and the temperature was decreased. At 370 °C and short austempering time, precipitation of carbides did not occur, while at 315 °C hexagonal carbides e appeared. The behavior of the activation energy, which increases with temperature, and the slower transformation kinetics at low temperatures seem to be related to the presence of carbides.
| Translated title of the contribution | Kinetic and microstructural study of the austenitic transformation during the austempering of ductile irons |
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| Original language | Spanish |
| Pages (from-to) | 227-233 |
| Number of pages | 7 |
| Journal | Informacion Tecnologica |
| Volume | 10 |
| Issue number | 2 |
| State | Published - 1999 |
| Externally published | Yes |