Resume: The prediction of microstructure during processing needs to characterize the phase transformation occurring during the thermal treatments and their kinetics. In-situ high-energy synchrotron x-ray diffraction experiments performed during temperature variations allow the characterization of the phase evolution. For some transformation conditions, the continuous recording of diffraction diagrams evidences clearly intermediate phases. The quantitative analysis of the diffraction diagrams gives the transformation kinetics of each phase as well as their cell parameters. Transformation kinetics obtained by this method are compared to results obtained by electrical resistivity.
Equipe: Département SI2M : Département SI2M : Microstructures et Contraintes
Selecting non-isothermal heat treatment schedules for precipitation hardening systems: An example of coupled process--property optimizationActa Materialia, 55(1):213-223
Resume: A physically based process model for the room temperature yield strength of an age-hardenable alloy subject to selected monotonic non-isothermal heat treatment schedules is developed and used to examine the possible efficiencies in processing and enhancements in strength that may be realistically achieved. `Processing Maps' are generated which illustrate both the yield strengths achievable and the processing routes necessary to achieve them, as well as estimates of the energy consumed in the thermal treatment. A Fe-2Cu (wt.%) alloy is used as an example and the results of physical experiments are compared with the model predictions. For the conditions examined, enhancements in yield strength of similar to 8% above those achievable in comparable isothermal treatments are illustrated with 65% of the energy input. Alternatively, similar yield strengths to those from comparable isothermal treatment are shown to be achievable with similar to 35% of the energy input. The physical origins of the observed effects and the potential implications of coupled process-property optimization are considered. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Equipe: Département SI2M : Microstructures et Contraintes